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4996 lines
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4996 lines
191 KiB
Plaintext
@c -*-texinfo-*-
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@c This is part of the GNU Emacs Lisp Reference Manual.
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@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001,
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@c 2002, 2005 Free Software Foundation, Inc.
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@c See the file elisp.texi for copying conditions.
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@setfilename ../info/display
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@node Display, System Interface, Processes, Top
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@chapter Emacs Display
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This chapter describes a number of features related to the display
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that Emacs presents to the user.
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@menu
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* Refresh Screen:: Clearing the screen and redrawing everything on it.
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* Forcing Redisplay:: Forcing redisplay.
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* Truncation:: Folding or wrapping long text lines.
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* The Echo Area:: Where messages are displayed.
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* Warnings:: Displaying warning messages for the user.
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* Progress:: Informing user about progress of a long operation.
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* Invisible Text:: Hiding part of the buffer text.
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* Selective Display:: Hiding part of the buffer text (the old way).
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* Temporary Displays:: Displays that go away automatically.
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* Overlays:: Use overlays to highlight parts of the buffer.
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* Width:: How wide a character or string is on the screen.
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* Line Height:: Controlling the height of lines.
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* Faces:: A face defines a graphics style for text characters:
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font, colors, etc.
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* Fringes:: Controlling window fringes.
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* Scroll Bars:: Controlling vertical scroll bars.
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* Pointer Shape:: Controlling the mouse pointer shape.
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* Display Property:: Enabling special display features.
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* Images:: Displaying images in Emacs buffers.
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* Buttons:: Adding clickable buttons to Emacs buffers.
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* Blinking:: How Emacs shows the matching open parenthesis.
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* Inverse Video:: Specifying how the screen looks.
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* Usual Display:: The usual conventions for displaying nonprinting chars.
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* Display Tables:: How to specify other conventions.
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* Beeping:: Audible signal to the user.
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* Window Systems:: Which window system is being used.
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@end menu
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@node Refresh Screen
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@section Refreshing the Screen
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The function @code{redraw-frame} clears and redisplays the entire
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contents of a given frame (@pxref{Frames}). This is useful if the
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screen is corrupted.
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@c Emacs 19 feature
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@defun redraw-frame frame
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This function clears and redisplays frame @var{frame}.
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@end defun
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Even more powerful is @code{redraw-display}:
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@deffn Command redraw-display
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This function clears and redisplays all visible frames.
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@end deffn
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This function calls for redisplay of certain windows, the next time
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redisplay is done, but does not clear them first.
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@defun force-window-update &optional object
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This function forces redisplay of some or all windows. If
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@var{object} is a window, it forces redisplay of that window. If
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@var{object} is a buffer or buffer name, it forces redisplay of all
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windows displaying that buffer. If @var{object} is @code{nil} (or
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omitted), it forces redisplay of all windows.
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@end defun
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Processing user input takes absolute priority over redisplay. If you
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call these functions when input is available, they do nothing
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immediately, but a full redisplay does happen eventually---after all the
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input has been processed.
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Normally, suspending and resuming Emacs also refreshes the screen.
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Some terminal emulators record separate contents for display-oriented
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programs such as Emacs and for ordinary sequential display. If you are
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using such a terminal, you might want to inhibit the redisplay on
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resumption.
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@defvar no-redraw-on-reenter
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@cindex suspend (cf. @code{no-redraw-on-reenter})
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@cindex resume (cf. @code{no-redraw-on-reenter})
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This variable controls whether Emacs redraws the entire screen after it
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has been suspended and resumed. Non-@code{nil} means there is no need
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to redraw, @code{nil} means redrawing is needed. The default is @code{nil}.
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@end defvar
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@node Forcing Redisplay
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@section Forcing Redisplay
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@cindex forcing redisplay
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Emacs redisplay normally stops if input arrives, and does not happen
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at all if input is available before it starts. Most of the time, this
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is exactly what you want. However, you can prevent preemption by
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binding @code{redisplay-dont-pause} to a non-@code{nil} value.
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@tindex redisplay-dont-pause
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@defvar redisplay-dont-pause
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If this variable is non-@code{nil}, pending input does not
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prevent or halt redisplay; redisplay occurs, and finishes,
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regardless of whether input is available.
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@end defvar
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You can request a display update, but only if no input is pending,
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with @code{(sit-for 0)}. To force a display update even when input is
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pending, do this:
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@example
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(let ((redisplay-dont-pause t))
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(sit-for 0))
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@end example
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@node Truncation
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@section Truncation
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@cindex line wrapping
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@cindex continuation lines
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@cindex @samp{$} in display
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@cindex @samp{\} in display
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When a line of text extends beyond the right edge of a window, the
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line can either be continued on the next screen line, or truncated to
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one screen line. The additional screen lines used to display a long
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text line are called @dfn{continuation} lines. Normally, a @samp{$} in
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the rightmost column of the window indicates truncation; a @samp{\} on
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the rightmost column indicates a line that ``wraps'' onto the next line,
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which is also called @dfn{continuing} the line. (The display table can
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specify alternative indicators; see @ref{Display Tables}.)
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On a window system display, the @samp{$} and @samp{\} indicators are
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replaced with arrow images displayed in the window fringes
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(@pxref{Fringes}).
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Note that continuation is different from filling; continuation happens
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on the screen only, not in the buffer contents, and it breaks a line
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precisely at the right margin, not at a word boundary. @xref{Filling}.
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@defopt truncate-lines
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This buffer-local variable controls how Emacs displays lines that extend
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beyond the right edge of the window. The default is @code{nil}, which
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specifies continuation. If the value is non-@code{nil}, then these
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lines are truncated.
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If the variable @code{truncate-partial-width-windows} is non-@code{nil},
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then truncation is always used for side-by-side windows (within one
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frame) regardless of the value of @code{truncate-lines}.
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@end defopt
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@defopt default-truncate-lines
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This variable is the default value for @code{truncate-lines}, for
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buffers that do not have buffer-local values for it.
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@end defopt
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@defopt truncate-partial-width-windows
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This variable controls display of lines that extend beyond the right
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edge of the window, in side-by-side windows (@pxref{Splitting Windows}).
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If it is non-@code{nil}, these lines are truncated; otherwise,
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@code{truncate-lines} says what to do with them.
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@end defopt
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When horizontal scrolling (@pxref{Horizontal Scrolling}) is in use in
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a window, that forces truncation.
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If your buffer contains @emph{very} long lines, and you use
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continuation to display them, just thinking about them can make Emacs
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redisplay slow. The column computation and indentation functions also
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become slow. Then you might find it advisable to set
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@code{cache-long-line-scans} to @code{t}.
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@defvar cache-long-line-scans
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If this variable is non-@code{nil}, various indentation and motion
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functions, and Emacs redisplay, cache the results of scanning the
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buffer, and consult the cache to avoid rescanning regions of the buffer
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unless they are modified.
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Turning on the cache slows down processing of short lines somewhat.
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This variable is automatically buffer-local in every buffer.
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@end defvar
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@node The Echo Area
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@section The Echo Area
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@cindex error display
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@cindex echo area
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The @dfn{echo area} is used for displaying error messages
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(@pxref{Errors}), for messages made with the @code{message} primitive,
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and for echoing keystrokes. It is not the same as the minibuffer,
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despite the fact that the minibuffer appears (when active) in the same
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place on the screen as the echo area. The @cite{GNU Emacs Manual}
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specifies the rules for resolving conflicts between the echo area and
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the minibuffer for use of that screen space (@pxref{Minibuffer,, The
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Minibuffer, emacs, The GNU Emacs Manual}).
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You can write output in the echo area by using the Lisp printing
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functions with @code{t} as the stream (@pxref{Output Functions}), or as
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follows:
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@defun message string &rest arguments
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This function displays a message in the echo area. The
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argument @var{string} is similar to a C language @code{printf} control
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string. See @code{format} in @ref{Formatting Strings}, for the details
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on the conversion specifications. @code{message} returns the
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constructed string.
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In batch mode, @code{message} prints the message text on the standard
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error stream, followed by a newline.
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If @var{string}, or strings among the @var{arguments}, have @code{face}
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text properties, these affect the way the message is displayed.
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@c Emacs 19 feature
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If @var{string} is @code{nil}, @code{message} clears the echo area; if
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the echo area has been expanded automatically, this brings it back to
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its normal size. If the minibuffer is active, this brings the
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minibuffer contents back onto the screen immediately.
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@vindex message-truncate-lines
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Normally, displaying a long message resizes the echo area to display
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the entire message. But if the variable @code{message-truncate-lines}
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is non-@code{nil}, the echo area does not resize, and the message is
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truncated to fit it, as in Emacs 20 and before.
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@example
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@group
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(message "Minibuffer depth is %d."
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(minibuffer-depth))
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@print{} Minibuffer depth is 0.
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@result{} "Minibuffer depth is 0."
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@end group
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@group
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---------- Echo Area ----------
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Minibuffer depth is 0.
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---------- Echo Area ----------
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@end group
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@end example
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To automatically display a message in the echo area or in a pop-buffer,
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depending on its size, use @code{display-message-or-buffer} (see below).
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@end defun
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@defopt max-mini-window-height
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This variable specifies the maximum height for resizing minibuffer
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windows. If a float, it specifies a fraction of the height of the
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frame. If an integer, it specifies a number of lines.
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@end defopt
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@tindex with-temp-message
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@defmac with-temp-message message &rest body
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This construct displays a message in the echo area temporarily, during
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the execution of @var{body}. It displays @var{message}, executes
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@var{body}, then returns the value of the last body form while restoring
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the previous echo area contents.
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@end defmac
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@defun message-or-box string &rest arguments
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This function displays a message like @code{message}, but may display it
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in a dialog box instead of the echo area. If this function is called in
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a command that was invoked using the mouse---more precisely, if
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@code{last-nonmenu-event} (@pxref{Command Loop Info}) is either
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@code{nil} or a list---then it uses a dialog box or pop-up menu to
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display the message. Otherwise, it uses the echo area. (This is the
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same criterion that @code{y-or-n-p} uses to make a similar decision; see
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@ref{Yes-or-No Queries}.)
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You can force use of the mouse or of the echo area by binding
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@code{last-nonmenu-event} to a suitable value around the call.
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@end defun
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@defun message-box string &rest arguments
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This function displays a message like @code{message}, but uses a dialog
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box (or a pop-up menu) whenever that is possible. If it is impossible
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to use a dialog box or pop-up menu, because the terminal does not
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support them, then @code{message-box} uses the echo area, like
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@code{message}.
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@end defun
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@defun display-message-or-buffer message &optional buffer-name not-this-window frame
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@tindex display-message-or-buffer
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This function displays the message @var{message}, which may be either a
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string or a buffer. If it is shorter than the maximum height of the
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echo area, as defined by @code{max-mini-window-height}, it is displayed
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in the echo area, using @code{message}. Otherwise,
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@code{display-buffer} is used to show it in a pop-up buffer.
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Returns either the string shown in the echo area, or when a pop-up
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buffer is used, the window used to display it.
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If @var{message} is a string, then the optional argument
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@var{buffer-name} is the name of the buffer used to display it when a
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pop-up buffer is used, defaulting to @samp{*Message*}. In the case
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where @var{message} is a string and displayed in the echo area, it is
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not specified whether the contents are inserted into the buffer anyway.
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The optional arguments @var{not-this-window} and @var{frame} are as for
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@code{display-buffer}, and only used if a buffer is displayed.
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@end defun
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@defun current-message
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This function returns the message currently being displayed in the
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echo area, or @code{nil} if there is none.
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@end defun
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@defvar cursor-in-echo-area
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This variable controls where the cursor appears when a message is
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displayed in the echo area. If it is non-@code{nil}, then the cursor
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appears at the end of the message. Otherwise, the cursor appears at
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point---not in the echo area at all.
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The value is normally @code{nil}; Lisp programs bind it to @code{t}
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for brief periods of time.
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@end defvar
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@defvar echo-area-clear-hook
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This normal hook is run whenever the echo area is cleared---either by
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@code{(message nil)} or for any other reason.
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@end defvar
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Almost all the messages displayed in the echo area are also recorded
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in the @samp{*Messages*} buffer.
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@defopt message-log-max
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This variable specifies how many lines to keep in the @samp{*Messages*}
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buffer. The value @code{t} means there is no limit on how many lines to
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keep. The value @code{nil} disables message logging entirely. Here's
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how to display a message and prevent it from being logged:
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@example
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(let (message-log-max)
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(message @dots{}))
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@end example
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@end defopt
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@defvar echo-keystrokes
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This variable determines how much time should elapse before command
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characters echo. Its value must be an integer or floating point number,
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which specifies the
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number of seconds to wait before echoing. If the user types a prefix
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key (such as @kbd{C-x}) and then delays this many seconds before
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continuing, the prefix key is echoed in the echo area. (Once echoing
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begins in a key sequence, all subsequent characters in the same key
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sequence are echoed immediately.)
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If the value is zero, then command input is not echoed.
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@end defvar
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@node Warnings
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@section Reporting Warnings
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@cindex warnings
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@dfn{Warnings} are a facility for a program to inform the user of a
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possible problem, but continue running.
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@menu
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* Warning Basics:: Warnings concepts and functions to report them.
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* Warning Variables:: Variables programs bind to customize their warnings.
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* Warning Options:: Variables users set to control display of warnings.
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@end menu
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@node Warning Basics
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@subsection Warning Basics
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@cindex severity level
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Every warning has a textual message, which explains the problem for
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the user, and a @dfn{severity level} which is a symbol. Here are the
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possible severity levels, in order of decreasing severity, and their
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meanings:
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@table @code
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@item :emergency
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A problem that will seriously impair Emacs operation soon
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if you do not attend to it promptly.
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@item :error
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A report of data or circumstances that are inherently wrong.
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@item :warning
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A report of data or circumstances that are not inherently wrong, but
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raise suspicion of a possible problem.
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@item :debug
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A report of information that may be useful if you are debugging.
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@end table
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When your program encounters invalid input data, it can either
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signal a Lisp error by calling @code{error} or @code{signal} or report
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a warning with severity @code{:error}. Signaling a Lisp error is the
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easiest thing to do, but it means the program cannot continue
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processing. If you want to take the trouble to implement a way to
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continue processing despite the bad data, then reporting a warning of
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severity @code{:error} is the right way to inform the user of the
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problem. For instance, the Emacs Lisp byte compiler can report an
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error that way and continue compiling other functions. (If the
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program signals a Lisp error and then handles it with
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@code{condition-case}, the user won't see the error message; it could
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show the message to the user by reporting it as a warning.)
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@cindex warning type
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Each warning has a @dfn{warning type} to classify it. The type is a
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list of symbols. The first symbol should be the custom group that you
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use for the program's user options. For example, byte compiler
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warnings use the warning type @code{(bytecomp)}. You can also
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subcategorize the warnings, if you wish, by using more symbols in the
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list.
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@defun display-warning type message &optional level buffer-name
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This function reports a warning, using @var{message} as the message
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and @var{type} as the warning type. @var{level} should be the
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severity level, with @code{:warning} being the default.
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@var{buffer-name}, if non-@code{nil}, specifies the name of the buffer
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for logging the warning. By default, it is @samp{*Warnings*}.
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@end defun
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@defun lwarn type level message &rest args
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This function reports a warning using the value of @code{(format
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@var{message} @var{args}...)} as the message. In other respects it is
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equivalent to @code{display-warning}.
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@end defun
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@defun warn message &rest args
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This function reports a warning using the value of @code{(format
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@var{message} @var{args}...)} as the message, @code{(emacs)} as the
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type, and @code{:warning} as the severity level. It exists for
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compatibility only; we recommend not using it, because you should
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specify a specific warning type.
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@end defun
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@node Warning Variables
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@subsection Warning Variables
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Programs can customize how their warnings appear by binding
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the variables described in this section.
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@defvar warning-levels
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This list defines the meaning and severity order of the warning
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severity levels. Each element defines one severity level,
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and they are arranged in order of decreasing severity.
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Each element has the form @code{(@var{level} @var{string}
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@var{function})}, where @var{level} is the severity level it defines.
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@var{string} specifies the textual description of this level.
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@var{string} should use @samp{%s} to specify where to put the warning
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type information, or it can omit the @samp{%s} so as not to include
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that information.
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The optional @var{function}, if non-@code{nil}, is a function to call
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with no arguments, to get the user's attention.
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Normally you should not change the value of this variable.
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@end defvar
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@defvar warning-prefix-function
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If non-@code{nil}, the value is a function to generate prefix text for
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warnings. Programs can bind the variable to a suitable function.
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@code{display-warning} calls this function with the warnings buffer
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current, and the function can insert text in it. That text becomes
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the beginning of the warning message.
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The function is called with two arguments, the severity level and its
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entry in @code{warning-levels}. It should return a list to use as the
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entry (this value need not be an actual member of
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@code{warning-levels}). By constructing this value, the function can
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change the severity of the warning, or specify different handling for
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a given severity level.
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If the variable's value is @code{nil} then there is no function
|
|
to call.
|
|
@end defvar
|
|
|
|
@defvar warning-series
|
|
Programs can bind this variable to @code{t} to say that the next
|
|
warning should begin a series. When several warnings form a series,
|
|
that means to leave point on the first warning of the series, rather
|
|
than keep moving it for each warning so that it appears on the last one.
|
|
The series ends when the local binding is unbound and
|
|
@code{warning-series} becomes @code{nil} again.
|
|
|
|
The value can also be a symbol with a function definition. That is
|
|
equivalent to @code{t}, except that the next warning will also call
|
|
the function with no arguments with the warnings buffer current. The
|
|
function can insert text which will serve as a header for the series
|
|
of warnings.
|
|
|
|
Once a series has begun, the value is a marker which points to the
|
|
buffer position in the warnings buffer of the start of the series.
|
|
|
|
The variable's normal value is @code{nil}, which means to handle
|
|
each warning separately.
|
|
@end defvar
|
|
|
|
@defvar warning-fill-prefix
|
|
When this variable is non-@code{nil}, it specifies a fill prefix to
|
|
use for filling each warning's text.
|
|
@end defvar
|
|
|
|
@defvar warning-type-format
|
|
This variable specifies the format for displaying the warning type
|
|
in the warning message. The result of formatting the type this way
|
|
gets included in the message under the control of the string in the
|
|
entry in @code{warning-levels}. The default value is @code{" (%s)"}.
|
|
If you bind it to @code{""} then the warning type won't appear at
|
|
all.
|
|
@end defvar
|
|
|
|
@node Warning Options
|
|
@subsection Warning Options
|
|
|
|
These variables are used by users to control what happens
|
|
when a Lisp program reports a warning.
|
|
|
|
@defopt warning-minimum-level
|
|
This user option specifies the minimum severity level that should be
|
|
shown immediately to the user. The default is @code{:warning}, which
|
|
means to immediately display all warnings except @code{:debug}
|
|
warnings.
|
|
@end defopt
|
|
|
|
@defopt warning-minimum-log-level
|
|
This user option specifies the minimum severity level that should be
|
|
logged in the warnings buffer. The default is @code{:warning}, which
|
|
means to log all warnings except @code{:debug} warnings.
|
|
@end defopt
|
|
|
|
@defopt warning-suppress-types
|
|
This list specifies which warning types should not be displayed
|
|
immediately for the user. Each element of the list should be a list
|
|
of symbols. If its elements match the first elements in a warning
|
|
type, then that warning is not displayed immediately.
|
|
@end defopt
|
|
|
|
@defopt warning-suppress-log-types
|
|
This list specifies which warning types should not be logged in the
|
|
warnings buffer. Each element of the list should be a list of
|
|
symbols. If it matches the first few elements in a warning type, then
|
|
that warning is not logged.
|
|
@end defopt
|
|
|
|
@node Progress
|
|
@section Reporting Operation Progress
|
|
@cindex progress reporting
|
|
|
|
When an operation can take a while to finish, you should inform the
|
|
user about the progress it makes. This way the user can estimate
|
|
remaining time and clearly see that Emacs is busy working, not hung.
|
|
|
|
Functions listed in this section provide simple and efficient way of
|
|
reporting operation progress. Here is a working example that does
|
|
nothing useful:
|
|
|
|
@smallexample
|
|
(let ((progress-reporter
|
|
(make-progress-reporter "Collecting mana for Emacs..."
|
|
0 500)))
|
|
(dotimes (k 500)
|
|
(sit-for 0.01)
|
|
(progress-reporter-update progress-reporter k))
|
|
(progress-reporter-done progress-reporter))
|
|
@end smallexample
|
|
|
|
@defun make-progress-reporter message min-value max-value &optional current-value min-change min-time
|
|
This function creates and returns a @dfn{progress reporter}---an
|
|
object you will use as an argument for all other functions listed
|
|
here. The idea is to precompute as much data as possible to make
|
|
progress reporting very fast.
|
|
|
|
When this progress reporter is subsequently used, it will display
|
|
@var{message} in the echo area, followed by progress percentage.
|
|
@var{message} is treated as a simple string. If you need it to depend
|
|
on a filename, for instance, use @code{format} before calling this
|
|
function.
|
|
|
|
@var{min-value} and @var{max-value} arguments stand for starting and
|
|
final states of your operation. For instance, if you scan a buffer,
|
|
they should be the results of @code{point-min} and @code{point-max}
|
|
correspondingly. It is required that @var{max-value} is greater than
|
|
@var{min-value}. If you create progress reporter when some part of
|
|
the operation has already been completed, then specify
|
|
@var{current-value} argument. But normally you should omit it or set
|
|
it to @code{nil}---it will default to @var{min-value} then.
|
|
|
|
Remaining arguments control the rate of echo area updates. Progress
|
|
reporter will wait for at least @var{min-change} more percents of the
|
|
operation to be completed before printing next message.
|
|
@var{min-time} specifies the minimum time in seconds to pass between
|
|
successive prints. It can be fractional. Depending on Emacs and
|
|
system capabilities, progress reporter may or may not respect this
|
|
last argument or do it with varying precision. Default value for
|
|
@var{min-change} is 1 (one percent), for @var{min-time}---0.2
|
|
(seconds.)
|
|
|
|
This function calls @code{progress-reporter-update}, so the first
|
|
message is printed immediately.
|
|
@end defun
|
|
|
|
@defun progress-reporter-update reporter value
|
|
This function does the main work of reporting progress of your
|
|
operation. It displays the message of @var{reporter}, followed by
|
|
progress percentage determined by @var{value}. If percentage is zero,
|
|
or close enough according to the @var{min-change} and @var{min-time}
|
|
arguments, then it is omitted from the output.
|
|
|
|
@var{reporter} must be the result of a call to
|
|
@code{make-progress-reporter}. @var{value} specifies the current
|
|
state of your operation and must be between @var{min-value} and
|
|
@var{max-value} (inclusive) as passed to
|
|
@code{make-progress-reporter}. For instance, if you scan a buffer,
|
|
then @var{value} should be the result of a call to @code{point}.
|
|
|
|
This function respects @var{min-change} and @var{min-time} as passed
|
|
to @code{make-progress-reporter} and so does not output new messages
|
|
on every invocation. It is thus very fast and normally you should not
|
|
try to reduce the number of calls to it: resulting overhead will most
|
|
likely negate your effort.
|
|
@end defun
|
|
|
|
@defun progress-reporter-force-update reporter value &optional new-message
|
|
This function is similar to @code{progress-reporter-update} except
|
|
that it prints a message in the echo area unconditionally.
|
|
|
|
The first two arguments have the same meaning as for
|
|
@code{progress-reporter-update}. Optional @var{new-message} allows
|
|
you to change the message of the @var{reporter}. Since this functions
|
|
always updates the echo area, such a change will be immediately
|
|
presented to the user.
|
|
@end defun
|
|
|
|
@defun progress-reporter-done reporter
|
|
This function should be called when the operation is finished. It
|
|
prints the message of @var{reporter} followed by word ``done'' in the
|
|
echo area.
|
|
|
|
You should always call this function and not hope for
|
|
@code{progress-reporter-update} to print ``100%.'' Firstly, it may
|
|
never print it, there are many good reasons for this not to happen.
|
|
Secondly, ``done'' is more explicit.
|
|
@end defun
|
|
|
|
@defmac dotimes-with-progress-reporter (var count [result]) message body...
|
|
This is a convenience macro that works the same way as @code{dotimes}
|
|
does, but also reports loop progress using the functions described
|
|
above. It allows you to save some typing.
|
|
|
|
You can rewrite the example in the beginning of this node using
|
|
this macro this way:
|
|
|
|
@example
|
|
(dotimes-with-progress-reporter
|
|
(k 500)
|
|
"Collecting some mana for Emacs..."
|
|
(sit-for 0.01))
|
|
@end example
|
|
@end defmac
|
|
|
|
@node Invisible Text
|
|
@section Invisible Text
|
|
|
|
@cindex invisible text
|
|
You can make characters @dfn{invisible}, so that they do not appear on
|
|
the screen, with the @code{invisible} property. This can be either a
|
|
text property (@pxref{Text Properties}) or a property of an overlay
|
|
(@pxref{Overlays}). Cursor motion also partly ignores these
|
|
characters; if the command loop finds point within them, it moves
|
|
point to the other side of them.
|
|
|
|
In the simplest case, any non-@code{nil} @code{invisible} property makes
|
|
a character invisible. This is the default case---if you don't alter
|
|
the default value of @code{buffer-invisibility-spec}, this is how the
|
|
@code{invisible} property works. You should normally use @code{t}
|
|
as the value of the @code{invisible} property if you don't plan
|
|
to set @code{buffer-invisibility-spec} yourself.
|
|
|
|
More generally, you can use the variable @code{buffer-invisibility-spec}
|
|
to control which values of the @code{invisible} property make text
|
|
invisible. This permits you to classify the text into different subsets
|
|
in advance, by giving them different @code{invisible} values, and
|
|
subsequently make various subsets visible or invisible by changing the
|
|
value of @code{buffer-invisibility-spec}.
|
|
|
|
Controlling visibility with @code{buffer-invisibility-spec} is
|
|
especially useful in a program to display the list of entries in a
|
|
database. It permits the implementation of convenient filtering
|
|
commands to view just a part of the entries in the database. Setting
|
|
this variable is very fast, much faster than scanning all the text in
|
|
the buffer looking for properties to change.
|
|
|
|
@defvar buffer-invisibility-spec
|
|
This variable specifies which kinds of @code{invisible} properties
|
|
actually make a character invisible. Setting this variable makes it
|
|
buffer-local.
|
|
|
|
@table @asis
|
|
@item @code{t}
|
|
A character is invisible if its @code{invisible} property is
|
|
non-@code{nil}. This is the default.
|
|
|
|
@item a list
|
|
Each element of the list specifies a criterion for invisibility; if a
|
|
character's @code{invisible} property fits any one of these criteria,
|
|
the character is invisible. The list can have two kinds of elements:
|
|
|
|
@table @code
|
|
@item @var{atom}
|
|
A character is invisible if its @code{invisible} property value
|
|
is @var{atom} or if it is a list with @var{atom} as a member.
|
|
|
|
@item (@var{atom} . t)
|
|
A character is invisible if its @code{invisible} property value
|
|
is @var{atom} or if it is a list with @var{atom} as a member.
|
|
Moreover, if this character is at the end of a line and is followed
|
|
by a visible newline, it displays an ellipsis.
|
|
@end table
|
|
@end table
|
|
@end defvar
|
|
|
|
Two functions are specifically provided for adding elements to
|
|
@code{buffer-invisibility-spec} and removing elements from it.
|
|
|
|
@defun add-to-invisibility-spec element
|
|
This function adds the element @var{element} to
|
|
@code{buffer-invisibility-spec}. If @code{buffer-invisibility-spec}
|
|
was @code{t}, it changes to a list, @code{(t)}, so that text whose
|
|
@code{invisible} property is @code{t} remains invisible.
|
|
@end defun
|
|
|
|
@defun remove-from-invisibility-spec element
|
|
This removes the element @var{element} from
|
|
@code{buffer-invisibility-spec}. This does nothing if @var{element}
|
|
is not in the list.
|
|
@end defun
|
|
|
|
A convention for use of @code{buffer-invisibility-spec} is that a
|
|
major mode should use the mode's own name as an element of
|
|
@code{buffer-invisibility-spec} and as the value of the
|
|
@code{invisible} property:
|
|
|
|
@example
|
|
;; @r{If you want to display an ellipsis:}
|
|
(add-to-invisibility-spec '(my-symbol . t))
|
|
;; @r{If you don't want ellipsis:}
|
|
(add-to-invisibility-spec 'my-symbol)
|
|
|
|
(overlay-put (make-overlay beginning end)
|
|
'invisible 'my-symbol)
|
|
|
|
;; @r{When done with the overlays:}
|
|
(remove-from-invisibility-spec '(my-symbol . t))
|
|
;; @r{Or respectively:}
|
|
(remove-from-invisibility-spec 'my-symbol)
|
|
@end example
|
|
|
|
@vindex line-move-ignore-invisible
|
|
Ordinarily, functions that operate on text or move point do not care
|
|
whether the text is invisible. The user-level line motion commands
|
|
explicitly ignore invisible newlines if
|
|
@code{line-move-ignore-invisible} is non-@code{nil} (the default), but
|
|
only because they are explicitly programmed to do so.
|
|
|
|
However, if a command ends with point inside or immediately after
|
|
invisible text, the main editing loop moves point further forward or
|
|
further backward (in the same direction that the command already moved
|
|
it) until that condition is no longer true. Thus, if the command
|
|
moved point back into an invisible range, Emacs moves point back to
|
|
the beginning of that range, following the previous visible character.
|
|
If the command moved point forward into an invisible range, Emacs
|
|
moves point forward past the first visible character that follows the
|
|
invisible text.
|
|
|
|
Incremental search can make invisible overlays visible temporarily
|
|
and/or permanently when a match includes invisible text. To enable
|
|
this, the overlay should have a non-@code{nil}
|
|
@code{isearch-open-invisible} property. The property value should be a
|
|
function to be called with the overlay as an argument. This function
|
|
should make the overlay visible permanently; it is used when the match
|
|
overlaps the overlay on exit from the search.
|
|
|
|
During the search, such overlays are made temporarily visible by
|
|
temporarily modifying their invisible and intangible properties. If you
|
|
want this to be done differently for a certain overlay, give it an
|
|
@code{isearch-open-invisible-temporary} property which is a function.
|
|
The function is called with two arguments: the first is the overlay, and
|
|
the second is @code{nil} to make the overlay visible, or @code{t} to
|
|
make it invisible again.
|
|
|
|
@node Selective Display
|
|
@section Selective Display
|
|
@cindex selective display
|
|
|
|
@dfn{Selective display} refers to a pair of related features for
|
|
hiding certain lines on the screen.
|
|
|
|
The first variant, explicit selective display, is designed for use
|
|
in a Lisp program: it controls which lines are hidden by altering the
|
|
text. This kind of hiding in some ways resembles the effect of the
|
|
@code{invisible} property (@pxref{Invisible Text}), but the two
|
|
features are different and do not work the same way.
|
|
|
|
In the second variant, the choice of lines to hide is made
|
|
automatically based on indentation. This variant is designed to be a
|
|
user-level feature.
|
|
|
|
The way you control explicit selective display is by replacing a
|
|
newline (control-j) with a carriage return (control-m). The text that
|
|
was formerly a line following that newline is now hidden. Strictly
|
|
speaking, it is temporarily no longer a line at all, since only
|
|
newlines can separate lines; it is now part of the previous line.
|
|
|
|
Selective display does not directly affect editing commands. For
|
|
example, @kbd{C-f} (@code{forward-char}) moves point unhesitatingly
|
|
into hidden text. However, the replacement of newline characters with
|
|
carriage return characters affects some editing commands. For
|
|
example, @code{next-line} skips hidden lines, since it searches only
|
|
for newlines. Modes that use selective display can also define
|
|
commands that take account of the newlines, or that control which
|
|
parts of the text are hidden.
|
|
|
|
When you write a selectively displayed buffer into a file, all the
|
|
control-m's are output as newlines. This means that when you next read
|
|
in the file, it looks OK, with nothing hidden. The selective display
|
|
effect is seen only within Emacs.
|
|
|
|
@defvar selective-display
|
|
This buffer-local variable enables selective display. This means that
|
|
lines, or portions of lines, may be made hidden.
|
|
|
|
@itemize @bullet
|
|
@item
|
|
If the value of @code{selective-display} is @code{t}, then the character
|
|
control-m marks the start of hidden text; the control-m, and the rest
|
|
of the line following it, are not displayed. This is explicit selective
|
|
display.
|
|
|
|
@item
|
|
If the value of @code{selective-display} is a positive integer, then
|
|
lines that start with more than that many columns of indentation are not
|
|
displayed.
|
|
@end itemize
|
|
|
|
When some portion of a buffer is hidden, the vertical movement
|
|
commands operate as if that portion did not exist, allowing a single
|
|
@code{next-line} command to skip any number of hidden lines.
|
|
However, character movement commands (such as @code{forward-char}) do
|
|
not skip the hidden portion, and it is possible (if tricky) to insert
|
|
or delete text in an hidden portion.
|
|
|
|
In the examples below, we show the @emph{display appearance} of the
|
|
buffer @code{foo}, which changes with the value of
|
|
@code{selective-display}. The @emph{contents} of the buffer do not
|
|
change.
|
|
|
|
@example
|
|
@group
|
|
(setq selective-display nil)
|
|
@result{} nil
|
|
|
|
---------- Buffer: foo ----------
|
|
1 on this column
|
|
2on this column
|
|
3n this column
|
|
3n this column
|
|
2on this column
|
|
1 on this column
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
|
|
@group
|
|
(setq selective-display 2)
|
|
@result{} 2
|
|
|
|
---------- Buffer: foo ----------
|
|
1 on this column
|
|
2on this column
|
|
2on this column
|
|
1 on this column
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
@end example
|
|
@end defvar
|
|
|
|
@defvar selective-display-ellipses
|
|
If this buffer-local variable is non-@code{nil}, then Emacs displays
|
|
@samp{@dots{}} at the end of a line that is followed by hidden text.
|
|
This example is a continuation of the previous one.
|
|
|
|
@example
|
|
@group
|
|
(setq selective-display-ellipses t)
|
|
@result{} t
|
|
|
|
---------- Buffer: foo ----------
|
|
1 on this column
|
|
2on this column ...
|
|
2on this column
|
|
1 on this column
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
@end example
|
|
|
|
You can use a display table to substitute other text for the ellipsis
|
|
(@samp{@dots{}}). @xref{Display Tables}.
|
|
@end defvar
|
|
|
|
@node Temporary Displays
|
|
@section Temporary Displays
|
|
|
|
Temporary displays are used by Lisp programs to put output into a
|
|
buffer and then present it to the user for perusal rather than for
|
|
editing. Many help commands use this feature.
|
|
|
|
@defspec with-output-to-temp-buffer buffer-name forms@dots{}
|
|
This function executes @var{forms} while arranging to insert any output
|
|
they print into the buffer named @var{buffer-name}, which is first
|
|
created if necessary, and put into Help mode. Finally, the buffer is
|
|
displayed in some window, but not selected.
|
|
|
|
If the @var{forms} do not change the major mode in the output buffer,
|
|
so that it is still Help mode at the end of their execution, then
|
|
@code{with-output-to-temp-buffer} makes this buffer read-only at the
|
|
end, and also scans it for function and variable names to make them
|
|
into clickable cross-references. @xref{Docstring hyperlinks, , Tips
|
|
for Documentation Strings}, in particular the item on hyperlinks in
|
|
documentation strings, for more details.
|
|
|
|
The string @var{buffer-name} specifies the temporary buffer, which
|
|
need not already exist. The argument must be a string, not a buffer.
|
|
The buffer is erased initially (with no questions asked), and it is
|
|
marked as unmodified after @code{with-output-to-temp-buffer} exits.
|
|
|
|
@code{with-output-to-temp-buffer} binds @code{standard-output} to the
|
|
temporary buffer, then it evaluates the forms in @var{forms}. Output
|
|
using the Lisp output functions within @var{forms} goes by default to
|
|
that buffer (but screen display and messages in the echo area, although
|
|
they are ``output'' in the general sense of the word, are not affected).
|
|
@xref{Output Functions}.
|
|
|
|
Several hooks are available for customizing the behavior
|
|
of this construct; they are listed below.
|
|
|
|
The value of the last form in @var{forms} is returned.
|
|
|
|
@example
|
|
@group
|
|
---------- Buffer: foo ----------
|
|
This is the contents of foo.
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
|
|
@group
|
|
(with-output-to-temp-buffer "foo"
|
|
(print 20)
|
|
(print standard-output))
|
|
@result{} #<buffer foo>
|
|
|
|
---------- Buffer: foo ----------
|
|
20
|
|
|
|
#<buffer foo>
|
|
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
@end example
|
|
@end defspec
|
|
|
|
@defvar temp-buffer-show-function
|
|
If this variable is non-@code{nil}, @code{with-output-to-temp-buffer}
|
|
calls it as a function to do the job of displaying a help buffer. The
|
|
function gets one argument, which is the buffer it should display.
|
|
|
|
It is a good idea for this function to run @code{temp-buffer-show-hook}
|
|
just as @code{with-output-to-temp-buffer} normally would, inside of
|
|
@code{save-selected-window} and with the chosen window and buffer
|
|
selected.
|
|
@end defvar
|
|
|
|
@defvar temp-buffer-setup-hook
|
|
@tindex temp-buffer-setup-hook
|
|
This normal hook is run by @code{with-output-to-temp-buffer} before
|
|
evaluating @var{body}. When the hook runs, the temporary buffer is
|
|
current. This hook is normally set up with a function to put the
|
|
buffer in Help mode.
|
|
@end defvar
|
|
|
|
@defvar temp-buffer-show-hook
|
|
This normal hook is run by @code{with-output-to-temp-buffer} after
|
|
displaying the temporary buffer. When the hook runs, the temporary buffer
|
|
is current, and the window it was displayed in is selected. This hook
|
|
is normally set up with a function to make the buffer read only, and
|
|
find function names and variable names in it, provided the major mode
|
|
is Help mode.
|
|
@end defvar
|
|
|
|
@defun momentary-string-display string position &optional char message
|
|
This function momentarily displays @var{string} in the current buffer at
|
|
@var{position}. It has no effect on the undo list or on the buffer's
|
|
modification status.
|
|
|
|
The momentary display remains until the next input event. If the next
|
|
input event is @var{char}, @code{momentary-string-display} ignores it
|
|
and returns. Otherwise, that event remains buffered for subsequent use
|
|
as input. Thus, typing @var{char} will simply remove the string from
|
|
the display, while typing (say) @kbd{C-f} will remove the string from
|
|
the display and later (presumably) move point forward. The argument
|
|
@var{char} is a space by default.
|
|
|
|
The return value of @code{momentary-string-display} is not meaningful.
|
|
|
|
If the string @var{string} does not contain control characters, you can
|
|
do the same job in a more general way by creating (and then subsequently
|
|
deleting) an overlay with a @code{before-string} property.
|
|
@xref{Overlay Properties}.
|
|
|
|
If @var{message} is non-@code{nil}, it is displayed in the echo area
|
|
while @var{string} is displayed in the buffer. If it is @code{nil}, a
|
|
default message says to type @var{char} to continue.
|
|
|
|
In this example, point is initially located at the beginning of the
|
|
second line:
|
|
|
|
@example
|
|
@group
|
|
---------- Buffer: foo ----------
|
|
This is the contents of foo.
|
|
@point{}Second line.
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
|
|
@group
|
|
(momentary-string-display
|
|
"**** Important Message! ****"
|
|
(point) ?\r
|
|
"Type RET when done reading")
|
|
@result{} t
|
|
@end group
|
|
|
|
@group
|
|
---------- Buffer: foo ----------
|
|
This is the contents of foo.
|
|
**** Important Message! ****Second line.
|
|
---------- Buffer: foo ----------
|
|
|
|
---------- Echo Area ----------
|
|
Type RET when done reading
|
|
---------- Echo Area ----------
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@node Overlays
|
|
@section Overlays
|
|
@cindex overlays
|
|
|
|
You can use @dfn{overlays} to alter the appearance of a buffer's text on
|
|
the screen, for the sake of presentation features. An overlay is an
|
|
object that belongs to a particular buffer, and has a specified
|
|
beginning and end. It also has properties that you can examine and set;
|
|
these affect the display of the text within the overlay.
|
|
|
|
An overlays uses markers to record its beginning and end; thus,
|
|
editing the text of the buffer adjusts the beginning and end of each
|
|
overlay so that it stays with the text. When you create the overlay,
|
|
you can specify whether text inserted at the beginning should be
|
|
inside the overlay or outside, and likewise for the end of the overlay.
|
|
|
|
@menu
|
|
* Managing Overlays:: Creating and moving overlays.
|
|
* Overlay Properties:: How to read and set properties.
|
|
What properties do to the screen display.
|
|
* Finding Overlays:: Searching for overlays.
|
|
@end menu
|
|
|
|
@node Managing Overlays
|
|
@subsection Managing Overlays
|
|
|
|
This section describes the functions to create, delete and move
|
|
overlays, and to examine their contents. Overlay changes are not
|
|
recorded in the buffer's undo list, since the overlays are not
|
|
part of the buffer's contents.
|
|
|
|
@defun overlayp object
|
|
This function returns @code{t} if @var{object} is an overlay.
|
|
@end defun
|
|
|
|
@defun make-overlay start end &optional buffer front-advance rear-advance
|
|
This function creates and returns an overlay that belongs to
|
|
@var{buffer} and ranges from @var{start} to @var{end}. Both @var{start}
|
|
and @var{end} must specify buffer positions; they may be integers or
|
|
markers. If @var{buffer} is omitted, the overlay is created in the
|
|
current buffer.
|
|
|
|
The arguments @var{front-advance} and @var{rear-advance} specify the
|
|
insertion type for the start of the overlay and for the end of the
|
|
overlay, respectively. @xref{Marker Insertion Types}. If
|
|
@var{front-advance} is non-@code{nil}, text inserted at the beginning
|
|
of the overlay is excluded from the overlay. If @var{read-advance} is
|
|
non-@code{nil}, text inserted at the beginning of the overlay is
|
|
included in the overlay.
|
|
@end defun
|
|
|
|
@defun overlay-start overlay
|
|
This function returns the position at which @var{overlay} starts,
|
|
as an integer.
|
|
@end defun
|
|
|
|
@defun overlay-end overlay
|
|
This function returns the position at which @var{overlay} ends,
|
|
as an integer.
|
|
@end defun
|
|
|
|
@defun overlay-buffer overlay
|
|
This function returns the buffer that @var{overlay} belongs to. It
|
|
returns @code{nil} if @var{overlay} has been deleted.
|
|
@end defun
|
|
|
|
@defun delete-overlay overlay
|
|
This function deletes @var{overlay}. The overlay continues to exist as
|
|
a Lisp object, and its property list is unchanged, but it ceases to be
|
|
attached to the buffer it belonged to, and ceases to have any effect on
|
|
display.
|
|
|
|
A deleted overlay is not permanently disconnected. You can give it a
|
|
position in a buffer again by calling @code{move-overlay}.
|
|
@end defun
|
|
|
|
@defun move-overlay overlay start end &optional buffer
|
|
This function moves @var{overlay} to @var{buffer}, and places its bounds
|
|
at @var{start} and @var{end}. Both arguments @var{start} and @var{end}
|
|
must specify buffer positions; they may be integers or markers.
|
|
|
|
If @var{buffer} is omitted, @var{overlay} stays in the same buffer it
|
|
was already associated with; if @var{overlay} was deleted, it goes into
|
|
the current buffer.
|
|
|
|
The return value is @var{overlay}.
|
|
|
|
This is the only valid way to change the endpoints of an overlay. Do
|
|
not try modifying the markers in the overlay by hand, as that fails to
|
|
update other vital data structures and can cause some overlays to be
|
|
``lost''.
|
|
@end defun
|
|
|
|
@defun remove-overlays &optional start end name value
|
|
This function removes all the overlays between @var{start} and
|
|
@var{end} whose property @var{name} has the value @var{value}. It can
|
|
move the endpoints of the overlays in the region, or split them.
|
|
|
|
If @var{name} is omitted or @code{nil}, it means to delete all overlays in
|
|
the specified region. If @var{start} and/or @var{end} are omitted or
|
|
@code{nil}, that means the beginning and end of the buffer respectively.
|
|
Therefore, @code{(remove-overlays)} removes all the overlays in the
|
|
current buffer.
|
|
@end defun
|
|
|
|
Here are some examples:
|
|
|
|
@example
|
|
;; @r{Create an overlay.}
|
|
(setq foo (make-overlay 1 10))
|
|
@result{} #<overlay from 1 to 10 in display.texi>
|
|
(overlay-start foo)
|
|
@result{} 1
|
|
(overlay-end foo)
|
|
@result{} 10
|
|
(overlay-buffer foo)
|
|
@result{} #<buffer display.texi>
|
|
;; @r{Give it a property we can check later.}
|
|
(overlay-put foo 'happy t)
|
|
@result{} t
|
|
;; @r{Verify the property is present.}
|
|
(overlay-get foo 'happy)
|
|
@result{} t
|
|
;; @r{Move the overlay.}
|
|
(move-overlay foo 5 20)
|
|
@result{} #<overlay from 5 to 20 in display.texi>
|
|
(overlay-start foo)
|
|
@result{} 5
|
|
(overlay-end foo)
|
|
@result{} 20
|
|
;; @r{Delete the overlay.}
|
|
(delete-overlay foo)
|
|
@result{} nil
|
|
;; @r{Verify it is deleted.}
|
|
foo
|
|
@result{} #<overlay in no buffer>
|
|
;; @r{A deleted overlay has no position.}
|
|
(overlay-start foo)
|
|
@result{} nil
|
|
(overlay-end foo)
|
|
@result{} nil
|
|
(overlay-buffer foo)
|
|
@result{} nil
|
|
;; @r{Undelete the overlay.}
|
|
(move-overlay foo 1 20)
|
|
@result{} #<overlay from 1 to 20 in display.texi>
|
|
;; @r{Verify the results.}
|
|
(overlay-start foo)
|
|
@result{} 1
|
|
(overlay-end foo)
|
|
@result{} 20
|
|
(overlay-buffer foo)
|
|
@result{} #<buffer display.texi>
|
|
;; @r{Moving and deleting the overlay does not change its properties.}
|
|
(overlay-get foo 'happy)
|
|
@result{} t
|
|
@end example
|
|
|
|
@node Overlay Properties
|
|
@subsection Overlay Properties
|
|
|
|
Overlay properties are like text properties in that the properties that
|
|
alter how a character is displayed can come from either source. But in
|
|
most respects they are different. @xref{Text Properties}, for comparison.
|
|
|
|
Text properties are considered a part of the text; overlays and
|
|
their properties are specifically considered not to be part of the
|
|
text. Thus, copying text between various buffers and strings
|
|
preserves text properties, but does not try to preserve overlays.
|
|
Changing a buffer's text properties marks the buffer as modified,
|
|
while moving an overlay or changing its properties does not. Unlike
|
|
text property changes, overlay property changes are not recorded in
|
|
the buffer's undo list.
|
|
|
|
These functions read and set the properties of an overlay:
|
|
|
|
@defun overlay-get overlay prop
|
|
This function returns the value of property @var{prop} recorded in
|
|
@var{overlay}, if any. If @var{overlay} does not record any value for
|
|
that property, but it does have a @code{category} property which is a
|
|
symbol, that symbol's @var{prop} property is used. Otherwise, the value
|
|
is @code{nil}.
|
|
@end defun
|
|
|
|
@defun overlay-put overlay prop value
|
|
This function sets the value of property @var{prop} recorded in
|
|
@var{overlay} to @var{value}. It returns @var{value}.
|
|
@end defun
|
|
|
|
@defun overlay-properties overlay
|
|
This returns a copy of the property list of @var{overlay}.
|
|
@end defun
|
|
|
|
See also the function @code{get-char-property} which checks both
|
|
overlay properties and text properties for a given character.
|
|
@xref{Examining Properties}.
|
|
|
|
Many overlay properties have special meanings; here is a table
|
|
of them:
|
|
|
|
@table @code
|
|
@item priority
|
|
@kindex priority @r{(overlay property)}
|
|
This property's value (which should be a nonnegative integer number)
|
|
determines the priority of the overlay. The priority matters when two
|
|
or more overlays cover the same character and both specify the same
|
|
property; the one whose @code{priority} value is larger takes priority
|
|
over the other. For the @code{face} property, the higher priority
|
|
value does not completely replace the other; instead, its face
|
|
attributes override the face attributes of the lower priority
|
|
@code{face} property.
|
|
|
|
Currently, all overlays take priority over text properties. Please
|
|
avoid using negative priority values, as we have not yet decided just
|
|
what they should mean.
|
|
|
|
@item window
|
|
@kindex window @r{(overlay property)}
|
|
If the @code{window} property is non-@code{nil}, then the overlay
|
|
applies only on that window.
|
|
|
|
@item category
|
|
@kindex category @r{(overlay property)}
|
|
If an overlay has a @code{category} property, we call it the
|
|
@dfn{category} of the overlay. It should be a symbol. The properties
|
|
of the symbol serve as defaults for the properties of the overlay.
|
|
|
|
@item face
|
|
@kindex face @r{(overlay property)}
|
|
This property controls the way text is displayed---for example, which
|
|
font and which colors. @xref{Faces}, for more information.
|
|
|
|
In the simplest case, the value is a face name. It can also be a list;
|
|
then each element can be any of these possibilities:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
A face name (a symbol or string).
|
|
|
|
@item
|
|
A property list of face attributes. This has the form (@var{keyword}
|
|
@var{value} @dots{}), where each @var{keyword} is a face attribute
|
|
name and @var{value} is a meaningful value for that attribute. With
|
|
this feature, you do not need to create a face each time you want to
|
|
specify a particular attribute for certain text. @xref{Face
|
|
Attributes}.
|
|
|
|
@item
|
|
A cons cell of the form @code{(foreground-color . @var{color-name})} or
|
|
@code{(background-color . @var{color-name})}. These elements specify
|
|
just the foreground color or just the background color.
|
|
|
|
@code{(foreground-color . @var{color-name})} has the same effect as
|
|
@code{(:foreground @var{color-name})}; likewise for the background.
|
|
@end itemize
|
|
|
|
@item mouse-face
|
|
@kindex mouse-face @r{(overlay property)}
|
|
This property is used instead of @code{face} when the mouse is within
|
|
the range of the overlay.
|
|
|
|
@item display
|
|
@kindex display @r{(overlay property)}
|
|
This property activates various features that change the
|
|
way text is displayed. For example, it can make text appear taller
|
|
or shorter, higher or lower, wider or narrower, or replaced with an image.
|
|
@xref{Display Property}.
|
|
|
|
@item help-echo
|
|
@kindex help-echo @r{(overlay property)}
|
|
If an overlay has a @code{help-echo} property, then when you move the
|
|
mouse onto the text in the overlay, Emacs displays a help string in the
|
|
echo area, or in the tooltip window. For details see @ref{Text
|
|
help-echo}.
|
|
|
|
@item modification-hooks
|
|
@kindex modification-hooks @r{(overlay property)}
|
|
This property's value is a list of functions to be called if any
|
|
character within the overlay is changed or if text is inserted strictly
|
|
within the overlay.
|
|
|
|
The hook functions are called both before and after each change.
|
|
If the functions save the information they receive, and compare notes
|
|
between calls, they can determine exactly what change has been made
|
|
in the buffer text.
|
|
|
|
When called before a change, each function receives four arguments: the
|
|
overlay, @code{nil}, and the beginning and end of the text range to be
|
|
modified.
|
|
|
|
When called after a change, each function receives five arguments: the
|
|
overlay, @code{t}, the beginning and end of the text range just
|
|
modified, and the length of the pre-change text replaced by that range.
|
|
(For an insertion, the pre-change length is zero; for a deletion, that
|
|
length is the number of characters deleted, and the post-change
|
|
beginning and end are equal.)
|
|
|
|
@item insert-in-front-hooks
|
|
@kindex insert-in-front-hooks @r{(overlay property)}
|
|
This property's value is a list of functions to be called before and
|
|
after inserting text right at the beginning of the overlay. The calling
|
|
conventions are the same as for the @code{modification-hooks} functions.
|
|
|
|
@item insert-behind-hooks
|
|
@kindex insert-behind-hooks @r{(overlay property)}
|
|
This property's value is a list of functions to be called before and
|
|
after inserting text right at the end of the overlay. The calling
|
|
conventions are the same as for the @code{modification-hooks} functions.
|
|
|
|
@item invisible
|
|
@kindex invisible @r{(overlay property)}
|
|
The @code{invisible} property can make the text in the overlay
|
|
invisible, which means that it does not appear on the screen.
|
|
@xref{Invisible Text}, for details.
|
|
|
|
@item intangible
|
|
@kindex intangible @r{(overlay property)}
|
|
The @code{intangible} property on an overlay works just like the
|
|
@code{intangible} text property. @xref{Special Properties}, for details.
|
|
|
|
@item isearch-open-invisible
|
|
This property tells incremental search how to make an invisible overlay
|
|
visible, permanently, if the final match overlaps it. @xref{Invisible
|
|
Text}.
|
|
|
|
@item isearch-open-invisible-temporary
|
|
This property tells incremental search how to make an invisible overlay
|
|
visible, temporarily, during the search. @xref{Invisible Text}.
|
|
|
|
@item before-string
|
|
@kindex before-string @r{(overlay property)}
|
|
This property's value is a string to add to the display at the beginning
|
|
of the overlay. The string does not appear in the buffer in any
|
|
sense---only on the screen.
|
|
|
|
@item after-string
|
|
@kindex after-string @r{(overlay property)}
|
|
This property's value is a string to add to the display at the end of
|
|
the overlay. The string does not appear in the buffer in any
|
|
sense---only on the screen.
|
|
|
|
@item evaporate
|
|
@kindex evaporate @r{(overlay property)}
|
|
If this property is non-@code{nil}, the overlay is deleted automatically
|
|
if it becomes empty (i.e., if its length becomes zero). If you give
|
|
an empty overlay a non-@code{nil} @code{evaporate} property, that deletes
|
|
it immediately.
|
|
|
|
@item local-map
|
|
@cindex keymap of character (and overlays)
|
|
@kindex local-map @r{(overlay property)}
|
|
If this property is non-@code{nil}, it specifies a keymap for a portion
|
|
of the text. The property's value replaces the buffer's local map, when
|
|
the character after point is within the overlay. @xref{Active Keymaps}.
|
|
|
|
@item keymap
|
|
@kindex keymap @r{(overlay property)}
|
|
The @code{keymap} property is similar to @code{local-map} but overrides the
|
|
buffer's local map (and the map specified by the @code{local-map}
|
|
property) rather than replacing it.
|
|
@end table
|
|
|
|
@node Finding Overlays
|
|
@subsection Searching for Overlays
|
|
|
|
@defun overlays-at pos
|
|
This function returns a list of all the overlays that cover the
|
|
character at position @var{pos} in the current buffer. The list is in
|
|
no particular order. An overlay contains position @var{pos} if it
|
|
begins at or before @var{pos}, and ends after @var{pos}.
|
|
|
|
To illustrate usage, here is a Lisp function that returns a list of the
|
|
overlays that specify property @var{prop} for the character at point:
|
|
|
|
@smallexample
|
|
(defun find-overlays-specifying (prop)
|
|
(let ((overlays (overlays-at (point)))
|
|
found)
|
|
(while overlays
|
|
(let ((overlay (car overlays)))
|
|
(if (overlay-get overlay prop)
|
|
(setq found (cons overlay found))))
|
|
(setq overlays (cdr overlays)))
|
|
found))
|
|
@end smallexample
|
|
@end defun
|
|
|
|
@defun overlays-in beg end
|
|
This function returns a list of the overlays that overlap the region
|
|
@var{beg} through @var{end}. ``Overlap'' means that at least one
|
|
character is contained within the overlay and also contained within the
|
|
specified region; however, empty overlays are included in the result if
|
|
they are located at @var{beg}, or strictly between @var{beg} and @var{end}.
|
|
@end defun
|
|
|
|
@defun next-overlay-change pos
|
|
This function returns the buffer position of the next beginning or end
|
|
of an overlay, after @var{pos}. If there is none, it returns
|
|
@code{(point-max)}.
|
|
@end defun
|
|
|
|
@defun previous-overlay-change pos
|
|
This function returns the buffer position of the previous beginning or
|
|
end of an overlay, before @var{pos}. If there is none, it returns
|
|
@code{(point-min)}.
|
|
@end defun
|
|
|
|
Here's an easy way to use @code{next-overlay-change} to search for the
|
|
next character which gets a non-@code{nil} @code{happy} property from
|
|
either its overlays or its text properties (@pxref{Property Search}):
|
|
|
|
@smallexample
|
|
(defun find-overlay-prop (prop)
|
|
(save-excursion
|
|
(while (and (not (eobp))
|
|
(not (get-char-property (point) 'happy)))
|
|
(goto-char (min (next-overlay-change (point))
|
|
(next-single-property-change (point) 'happy))))
|
|
(point)))
|
|
@end smallexample
|
|
|
|
@node Width
|
|
@section Width
|
|
|
|
Since not all characters have the same width, these functions let you
|
|
check the width of a character. @xref{Primitive Indent}, and
|
|
@ref{Screen Lines}, for related functions.
|
|
|
|
@defun char-width char
|
|
This function returns the width in columns of the character @var{char},
|
|
if it were displayed in the current buffer and the selected window.
|
|
@end defun
|
|
|
|
@defun string-width string
|
|
This function returns the width in columns of the string @var{string},
|
|
if it were displayed in the current buffer and the selected window.
|
|
@end defun
|
|
|
|
@defun truncate-string-to-width string width &optional start-column padding ellipsis
|
|
This function returns the part of @var{string} that fits within
|
|
@var{width} columns, as a new string.
|
|
|
|
If @var{string} does not reach @var{width}, then the result ends where
|
|
@var{string} ends. If one multi-column character in @var{string}
|
|
extends across the column @var{width}, that character is not included in
|
|
the result. Thus, the result can fall short of @var{width} but cannot
|
|
go beyond it.
|
|
|
|
The optional argument @var{start-column} specifies the starting column.
|
|
If this is non-@code{nil}, then the first @var{start-column} columns of
|
|
the string are omitted from the value. If one multi-column character in
|
|
@var{string} extends across the column @var{start-column}, that
|
|
character is not included.
|
|
|
|
The optional argument @var{padding}, if non-@code{nil}, is a padding
|
|
character added at the beginning and end of the result string, to extend
|
|
it to exactly @var{width} columns. The padding character is used at the
|
|
end of the result if it falls short of @var{width}. It is also used at
|
|
the beginning of the result if one multi-column character in
|
|
@var{string} extends across the column @var{start-column}.
|
|
|
|
If @var{ellipsis} is non-@code{nil}, it should be a string which will
|
|
replace the end of @var{str} (including any padding) if it extends
|
|
beyond @var{end-column}, unless the display width of @var{str} is
|
|
equal to or less than the display width of @var{ellipsis}. If
|
|
@var{ellipsis} is non-@code{nil} and not a string, it stands for
|
|
@code{"..."}.
|
|
|
|
@example
|
|
(truncate-string-to-width "\tab\t" 12 4)
|
|
@result{} "ab"
|
|
(truncate-string-to-width "\tab\t" 12 4 ?\s)
|
|
@result{} " ab "
|
|
@end example
|
|
@end defun
|
|
|
|
@node Line Height
|
|
@section Line Height
|
|
@cindex line height
|
|
|
|
The total height of each display line consists of the height of the
|
|
contents of the line, and additional vertical line spacing below the
|
|
display row.
|
|
|
|
The height of the line contents is normally determined from the
|
|
maximum height of any character or image on that display line,
|
|
including the final newline if there is one. (A line that is
|
|
continued doesn't include a final newline.) In the most common case,
|
|
the line height equals the height of the default frame font.
|
|
|
|
There are several ways to explicitly control or change the line
|
|
height, either by specifying an absolute height for the display line,
|
|
or by adding additional vertical space below one or all lines.
|
|
|
|
@kindex line-height @r{(text property)}
|
|
A newline can have a @code{line-height} text or overlay property
|
|
that controls the total height of the display line ending in that
|
|
newline.
|
|
|
|
If the property value is a list @code{(@var{height} @var{total})},
|
|
then @var{height} is used as the actual property value for the
|
|
@code{line-height}, and @var{total} specifies the total displayed
|
|
height of the line, so the line spacing added below the line equals
|
|
the @var{total} height minus the actual line height. In this case,
|
|
the other ways to specify the line spacing are ignored.
|
|
|
|
If the property value is @code{t}, the displayed height of the
|
|
line is exactly what its contents demand; no line-spacing is added.
|
|
This case is useful for tiling small images or image slices without
|
|
adding blank areas between the images.
|
|
|
|
If the property value is not @code{t}, it is a height spec. A height
|
|
spec stands for a numeric height value; this height spec specifies the
|
|
actual line height, @var{line-height}. There are several ways to
|
|
write a height spec; here's how each of them translates into a numeric
|
|
height:
|
|
|
|
@table @code
|
|
@item @var{integer}
|
|
If the height spec is a positive integer, the height value is that integer.
|
|
@item @var{float}
|
|
If the height spec is a float, @var{float}, the numeric height value
|
|
is @var{float} times the frame's default line height.
|
|
@item (@var{face} . @var{ratio})
|
|
If the height spec is a cons of the format shown, the numeric height
|
|
is @var{ratio} times the height of face @var{face}. @var{ratio} can
|
|
be any type of number, or @code{nil} which means a ratio of 1.
|
|
If @var{face} is @code{t}, it refers to the current face.
|
|
@item (nil . @var{ratio})
|
|
If the height spec is a cons of the format shown, the numeric height
|
|
is @var{ratio} times the height of the contents of the line.
|
|
@end table
|
|
|
|
Thus, any valid non-@code{t} property value specifies a height in pixels,
|
|
@var{line-height}, one way or another. If the line contents' height
|
|
is less than @var{line-height}, Emacs adds extra vertical space above
|
|
the line to achieve the total height @var{line-height}. Otherwise,
|
|
@var{line-height} has no effect.
|
|
|
|
If you don't specify the @code{line-height} property, the line's
|
|
height consists of the contents' height plus the line spacing.
|
|
There are several ways to specify the line spacing for different
|
|
parts of Emacs text.
|
|
|
|
@vindex default-line-spacing
|
|
You can specify the line spacing for all lines in a frame with the
|
|
@code{line-spacing} frame parameter, @xref{Window Frame Parameters}.
|
|
However, if the variable @code{default-line-spacing} is
|
|
non-@code{nil}, it overrides the frame's @code{line-spacing}
|
|
parameter. An integer value specifies the number of pixels put below
|
|
lines on window systems. A floating point number specifies the
|
|
spacing relative to the frame's default line height.
|
|
|
|
@vindex line-spacing
|
|
You can specify the line spacing for all lines in a buffer via the
|
|
buffer-local @code{line-spacing} variable. An integer value specifies
|
|
the number of pixels put below lines on window systems. A floating
|
|
point number specifies the spacing relative to the default frame line
|
|
height. This overrides line spacings specified for the frame.
|
|
|
|
@kindex line-spacing @r{(text property)}
|
|
Finally, a newline can have a @code{line-spacing} text or overlay
|
|
property that controls the height of the display line ending with that
|
|
newline. The property value overrides the default frame line spacing
|
|
and the buffer local @code{line-spacing} variable.
|
|
|
|
One way or another, these mechanisms specify a Lisp value for the
|
|
spacing of each line. The value is a height spec, and it translates
|
|
into a Lisp value as described above. However, in this case the
|
|
numeric height value specifies the line spacing, rather than the line
|
|
height.
|
|
|
|
@node Faces
|
|
@section Faces
|
|
@cindex faces
|
|
|
|
A @dfn{face} is a named collection of graphical attributes: font
|
|
family, foreground color, background color, optional underlining, and
|
|
many others. Faces are used in Emacs to control the style of display of
|
|
particular parts of the text or the frame.
|
|
|
|
@cindex face id
|
|
Each face has its own @dfn{face number}, which distinguishes faces at
|
|
low levels within Emacs. However, for most purposes, you refer to
|
|
faces in Lisp programs by their names.
|
|
|
|
@defun facep object
|
|
This function returns @code{t} if @var{object} is a face name symbol (or
|
|
if it is a vector of the kind used internally to record face data). It
|
|
returns @code{nil} otherwise.
|
|
@end defun
|
|
|
|
Each face name is meaningful for all frames, and by default it has the
|
|
same meaning in all frames. But you can arrange to give a particular
|
|
face name a special meaning in one frame if you wish.
|
|
|
|
@menu
|
|
* Standard Faces:: The faces Emacs normally comes with.
|
|
* Defining Faces:: How to define a face with @code{defface}.
|
|
* Face Attributes:: What is in a face?
|
|
* Attribute Functions:: Functions to examine and set face attributes.
|
|
* Displaying Faces:: How Emacs combines the faces specified for a character.
|
|
* Font Selection:: Finding the best available font for a face.
|
|
* Face Functions:: How to define and examine faces.
|
|
* Auto Faces:: Hook for automatic face assignment.
|
|
* Font Lookup:: Looking up the names of available fonts
|
|
and information about them.
|
|
* Fontsets:: A fontset is a collection of fonts
|
|
that handle a range of character sets.
|
|
@end menu
|
|
|
|
@node Standard Faces
|
|
@subsection Standard Faces
|
|
|
|
This table lists all the standard faces and their uses. Most of them
|
|
are used for displaying certain parts of the frames or certain kinds of
|
|
text; you can control how those places look by customizing these faces.
|
|
|
|
@table @code
|
|
@item default
|
|
@kindex default @r{(face name)}
|
|
This face is used for ordinary text.
|
|
|
|
@item mode-line
|
|
@kindex mode-line @r{(face name)}
|
|
This face is used for the mode line of the selected window, and for
|
|
menu bars when toolkit menus are not used---but only if
|
|
@code{mode-line-inverse-video} is non-@code{nil}.
|
|
|
|
@item modeline
|
|
@kindex modeline @r{(face name)}
|
|
This is an alias for the @code{mode-line} face, for compatibility with
|
|
old Emacs versions.
|
|
|
|
@item mode-line-inactive
|
|
@kindex mode-line-inactive @r{(face name)}
|
|
This face is used for mode lines of non-selected windows.
|
|
This face inherits from @code{mode-line}, so changes
|
|
in that face affect all windows.
|
|
|
|
@item header-line
|
|
@kindex header-line @r{(face name)}
|
|
This face is used for the header lines of windows that have them.
|
|
|
|
@item menu
|
|
This face controls the display of menus, both their colors and their
|
|
font. (This works only on certain systems.)
|
|
|
|
@item fringe
|
|
@kindex fringe @r{(face name)}
|
|
This face controls the default colors of window fringes, the thin
|
|
areas on either side that are used to display continuation and
|
|
truncation glyphs. Other faces used to display bitmaps in the fringe
|
|
are implicitly merged with this face.
|
|
|
|
@item minibuffer-prompt
|
|
@kindex minibuffer-prompt @r{(face name)}
|
|
@vindex minibuffer-prompt-properties
|
|
This face is used for the text of minibuffer prompts. By default,
|
|
Emacs automatically adds this face to the value of
|
|
@code{minibuffer-prompt-properties}, which is a list of text
|
|
properties used to display the prompt text.
|
|
|
|
@item scroll-bar
|
|
@kindex scroll-bar @r{(face name)}
|
|
This face controls the colors for display of scroll bars.
|
|
|
|
@item tool-bar
|
|
@kindex tool-bar @r{(face name)}
|
|
This face is used for display of the tool bar, if any.
|
|
|
|
@item region
|
|
@kindex region @r{(face name)}
|
|
This face is used for highlighting the region in Transient Mark mode.
|
|
|
|
@item secondary-selection
|
|
@kindex secondary-selection @r{(face name)}
|
|
This face is used to show any secondary selection you have made.
|
|
|
|
@item highlight
|
|
@kindex highlight @r{(face name)}
|
|
This face is meant to be used for highlighting for various purposes.
|
|
|
|
@item mode-line-highlight
|
|
@kindex mode-line-highlight @r{(face name)}
|
|
This face is used for highlighting something on @code{mode-line} or
|
|
@code{header-line} for various purposes.
|
|
|
|
@item trailing-whitespace
|
|
@kindex trailing-whitespace @r{(face name)}
|
|
This face is used to display excess whitespace at the end of a line,
|
|
if @code{show-trailing-whitespace} is non-@code{nil}.
|
|
|
|
@item escape-glyph
|
|
@kindex escape-glyph @r{(face name)}
|
|
This face is used to display control characters and escape glyphs.
|
|
@end table
|
|
|
|
In contrast, these faces are provided to change the appearance of text
|
|
in specific ways. You can use them on specific text, when you want
|
|
the effects they produce.
|
|
|
|
@table @code
|
|
@item bold
|
|
@kindex bold @r{(face name)}
|
|
This face uses a bold font, if possible. It uses the bold variant of
|
|
the frame's font, if it has one. It's up to you to choose a default
|
|
font that has a bold variant, if you want to use one.
|
|
|
|
@item italic
|
|
@kindex italic @r{(face name)}
|
|
This face uses the italic variant of the frame's font, if it has one.
|
|
|
|
@item bold-italic
|
|
@kindex bold-italic @r{(face name)}
|
|
This face uses the bold italic variant of the frame's font, if it has
|
|
one.
|
|
|
|
@item underline
|
|
@kindex underline @r{(face name)}
|
|
This face underlines text.
|
|
|
|
@item fixed-pitch
|
|
@kindex fixed-pitch @r{(face name)}
|
|
This face forces use of a particular fixed-width font.
|
|
|
|
@item variable-pitch
|
|
@kindex variable-pitch @r{(face name)}
|
|
This face forces use of a particular variable-width font. It's
|
|
reasonable to customize this to use a different variable-width font, if
|
|
you like, but you should not make it a fixed-width font.
|
|
|
|
@item shadow
|
|
@kindex shadow @r{(face name)}
|
|
This face is used for making the text less noticeable than the
|
|
surrounding ordinary text.
|
|
@end table
|
|
|
|
@defvar show-trailing-whitespace
|
|
@tindex show-trailing-whitespace
|
|
If this variable is non-@code{nil}, Emacs uses the
|
|
@code{trailing-whitespace} face to display any spaces and tabs at the
|
|
end of a line.
|
|
@end defvar
|
|
|
|
@node Defining Faces
|
|
@subsection Defining Faces
|
|
|
|
The way to define a new face is with @code{defface}. This creates a
|
|
kind of customization item (@pxref{Customization}) which the user can
|
|
customize using the Customization buffer (@pxref{Easy Customization,,,
|
|
emacs, The GNU Emacs Manual}).
|
|
|
|
@defmac defface face spec doc [keyword value]...
|
|
This declares @var{face} as a customizable face that defaults
|
|
according to @var{spec}. You should not quote the symbol @var{face},
|
|
and it should not end in @samp{-face} (that would be redundant). The
|
|
argument @var{doc} specifies the face documentation. The keywords you
|
|
can use in @code{defface} are the same as in @code{defgroup} and
|
|
@code{defcustom} (@pxref{Common Keywords}).
|
|
|
|
When @code{defface} executes, it defines the face according to
|
|
@var{spec}, then uses any customizations that were read from the
|
|
init file (@pxref{Init File}) to override that specification.
|
|
|
|
The purpose of @var{spec} is to specify how the face should appear on
|
|
different kinds of terminals. It should be an alist whose elements
|
|
have the form @code{(@var{display} @var{atts})}. Each element's
|
|
@sc{car}, @var{display}, specifies a class of terminals. (The first
|
|
element, if it s @sc{car} is @code{default}, is special---it specifies
|
|
defaults for the remaining elements). The element's @sc{cadr},
|
|
@var{atts}, is a list of face attributes and their values; it
|
|
specifies what the face should look like on that kind of terminal.
|
|
The possible attributes are defined in the value of
|
|
@code{custom-face-attributes}.
|
|
|
|
The @var{display} part of an element of @var{spec} determines which
|
|
frames the element matches. If more than one element of @var{spec}
|
|
matches a given frame, the first element that matches is the one used
|
|
for that frame. There are three possibilities for @var{display}:
|
|
|
|
@table @asis
|
|
@item @code{default}
|
|
This element of @var{spec} doesn't match any frames; instead, it
|
|
specifies defaults that apply to all frames. This kind of element, if
|
|
used, must be the first element of @var{spec}. Each of the following
|
|
elements can override any or all of these defaults.
|
|
|
|
@item @code{t}
|
|
This element of @var{spec} matches all frames. Therefore, any
|
|
subsequent elements of @var{spec} are never used. Normally
|
|
@code{t} is used in the last (or only) element of @var{spec}.
|
|
|
|
@item a list
|
|
If @var{display} is a list, each element should have the form
|
|
@code{(@var{characteristic} @var{value}@dots{})}. Here
|
|
@var{characteristic} specifies a way of classifying frames, and the
|
|
@var{value}s are possible classifications which @var{display} should
|
|
apply to. Here are the possible values of @var{characteristic}:
|
|
|
|
@table @code
|
|
@item type
|
|
The kind of window system the frame uses---either @code{graphic} (any
|
|
graphics-capable display), @code{x}, @code{pc} (for the MS-DOS console),
|
|
@code{w32} (for MS Windows 9X/NT), or @code{tty} (a non-graphics-capable
|
|
display).
|
|
|
|
@item class
|
|
What kinds of colors the frame supports---either @code{color},
|
|
@code{grayscale}, or @code{mono}.
|
|
|
|
@item background
|
|
The kind of background---either @code{light} or @code{dark}.
|
|
|
|
@item min-colors
|
|
An integer that represents the minimum number of colors the frame
|
|
should support. This matches a frame if its
|
|
@code{display-color-cells} value is at least the specified integer.
|
|
|
|
@item supports
|
|
Whether or not the frame can display the face attributes given in
|
|
@var{value}@dots{} (@pxref{Face Attributes}). See the documentation
|
|
for the function @code{display-supports-face-attributes-p} for more
|
|
information on exactly how this testing is done. @xref{Display Face
|
|
Attribute Testing}.
|
|
@end table
|
|
|
|
If an element of @var{display} specifies more than one @var{value} for a
|
|
given @var{characteristic}, any of those values is acceptable. If
|
|
@var{display} has more than one element, each element should specify a
|
|
different @var{characteristic}; then @emph{each} characteristic of the
|
|
frame must match one of the @var{value}s specified for it in
|
|
@var{display}.
|
|
@end table
|
|
@end defmac
|
|
|
|
Here's how the standard face @code{region} is defined:
|
|
|
|
@example
|
|
@group
|
|
'((((class color) (min-colors 88) (background dark))
|
|
:background "blue3")
|
|
@end group
|
|
(((class color) (min-colors 88) (background light))
|
|
:background "lightgoldenrod2")
|
|
(((class color) (min-colors 16) (background dark))
|
|
:background "blue3")
|
|
(((class color) (min-colors 16) (background light))
|
|
:background "lightgoldenrod2")
|
|
(((class color) (min-colors 8))
|
|
:background "blue" :foreground "white")
|
|
(((type tty) (class mono))
|
|
:inverse-video t)
|
|
(t :background "gray"))
|
|
@group
|
|
"Basic face for highlighting the region."
|
|
:group 'basic-faces)
|
|
@end group
|
|
@end example
|
|
|
|
Internally, @code{defface} uses the symbol property
|
|
@code{face-defface-spec} to record the face attributes specified in
|
|
@code{defface}, @code{saved-face} for the attributes saved by the user
|
|
with the customization buffer, @code{customized-face} for the
|
|
attributes customized by the user for the current session, but not
|
|
saved, and @code{face-documentation} for the documentation string.
|
|
|
|
@defopt frame-background-mode
|
|
This option, if non-@code{nil}, specifies the background type to use for
|
|
interpreting face definitions. If it is @code{dark}, then Emacs treats
|
|
all frames as if they had a dark background, regardless of their actual
|
|
background colors. If it is @code{light}, then Emacs treats all frames
|
|
as if they had a light background.
|
|
@end defopt
|
|
|
|
@node Face Attributes
|
|
@subsection Face Attributes
|
|
@cindex face attributes
|
|
|
|
The effect of using a face is determined by a fixed set of @dfn{face
|
|
attributes}. This table lists all the face attributes, and what they
|
|
mean. Note that in general, more than one face can be specified for a
|
|
given piece of text; when that happens, the attributes of all the faces
|
|
are merged to specify how to display the text. @xref{Displaying Faces}.
|
|
|
|
Any attribute in a face can have the value @code{unspecified}. This
|
|
means the face doesn't specify that attribute. In face merging, when
|
|
the first face fails to specify a particular attribute, that means the
|
|
next face gets a chance. However, the @code{default} face must
|
|
specify all attributes.
|
|
|
|
Some of these font attributes are meaningful only on certain kinds of
|
|
displays---if your display cannot handle a certain attribute, the
|
|
attribute is ignored. (The attributes @code{:family}, @code{:width},
|
|
@code{:height}, @code{:weight}, and @code{:slant} correspond to parts of
|
|
an X Logical Font Descriptor.)
|
|
|
|
@table @code
|
|
@item :family
|
|
Font family name, or fontset name (@pxref{Fontsets}). If you specify a
|
|
font family name, the wild-card characters @samp{*} and @samp{?} are
|
|
allowed.
|
|
|
|
@item :width
|
|
Relative proportionate width, also known as the character set width or
|
|
set width. This should be one of the symbols @code{ultra-condensed},
|
|
@code{extra-condensed}, @code{condensed}, @code{semi-condensed},
|
|
@code{normal}, @code{semi-expanded}, @code{expanded},
|
|
@code{extra-expanded}, or @code{ultra-expanded}.
|
|
|
|
@item :height
|
|
Either the font height, an integer in units of 1/10 point, a floating
|
|
point number specifying the amount by which to scale the height of any
|
|
underlying face, or a function, which is called with the old height
|
|
(from the underlying face), and should return the new height.
|
|
|
|
@item :weight
|
|
Font weight---a symbol from this series (from most dense to most faint):
|
|
@code{ultra-bold}, @code{extra-bold}, @code{bold}, @code{semi-bold},
|
|
@code{normal}, @code{semi-light}, @code{light}, @code{extra-light},
|
|
or @code{ultra-light}.
|
|
|
|
On a text-only terminal, any weight greater than normal is displayed as
|
|
extra bright, and any weight less than normal is displayed as
|
|
half-bright (provided the terminal supports the feature).
|
|
|
|
@item :slant
|
|
Font slant---one of the symbols @code{italic}, @code{oblique}, @code{normal},
|
|
@code{reverse-italic}, or @code{reverse-oblique}.
|
|
|
|
On a text-only terminal, slanted text is displayed as half-bright, if
|
|
the terminal supports the feature.
|
|
|
|
@item :foreground
|
|
Foreground color, a string. The value can be a system-defined color
|
|
name, or a hexadecimal color specification of the form
|
|
@samp{#@var{rr}@var{gg}@var{bb}}. (@samp{#000000} is black,
|
|
@samp{#ff0000} is red, @samp{#00ff00} is green, @samp{#0000ff} is
|
|
blue, and @samp{#ffffff} is white.)
|
|
|
|
@item :background
|
|
Background color, a string, like the foreground color.
|
|
|
|
@item :inverse-video
|
|
Whether or not characters should be displayed in inverse video. The
|
|
value should be @code{t} (yes) or @code{nil} (no).
|
|
|
|
@item :stipple
|
|
The background stipple, a bitmap.
|
|
|
|
The value can be a string; that should be the name of a file containing
|
|
external-format X bitmap data. The file is found in the directories
|
|
listed in the variable @code{x-bitmap-file-path}.
|
|
|
|
Alternatively, the value can specify the bitmap directly, with a list
|
|
of the form @code{(@var{width} @var{height} @var{data})}. Here,
|
|
@var{width} and @var{height} specify the size in pixels, and
|
|
@var{data} is a string containing the raw bits of the bitmap, row by
|
|
row. Each row occupies @math{(@var{width} + 7) / 8} consecutive bytes
|
|
in the string (which should be a unibyte string for best results).
|
|
This means that each row always occupies at least one whole byte.
|
|
|
|
If the value is @code{nil}, that means use no stipple pattern.
|
|
|
|
Normally you do not need to set the stipple attribute, because it is
|
|
used automatically to handle certain shades of gray.
|
|
|
|
@item :underline
|
|
Whether or not characters should be underlined, and in what color. If
|
|
the value is @code{t}, underlining uses the foreground color of the
|
|
face. If the value is a string, underlining uses that color. The
|
|
value @code{nil} means do not underline.
|
|
|
|
@item :overline
|
|
Whether or not characters should be overlined, and in what color.
|
|
The value is used like that of @code{:underline}.
|
|
|
|
@item :strike-through
|
|
Whether or not characters should be strike-through, and in what
|
|
color. The value is used like that of @code{:underline}.
|
|
|
|
@item :inherit
|
|
The name of a face from which to inherit attributes, or a list of face
|
|
names. Attributes from inherited faces are merged into the face like an
|
|
underlying face would be, with higher priority than underlying faces.
|
|
If a list of faces is used, attributes from faces earlier in the list
|
|
override those from later faces.
|
|
|
|
@item :box
|
|
Whether or not a box should be drawn around characters, its color, the
|
|
width of the box lines, and 3D appearance.
|
|
@end table
|
|
|
|
Here are the possible values of the @code{:box} attribute, and what
|
|
they mean:
|
|
|
|
@table @asis
|
|
@item @code{nil}
|
|
Don't draw a box.
|
|
|
|
@item @code{t}
|
|
Draw a box with lines of width 1, in the foreground color.
|
|
|
|
@item @var{color}
|
|
Draw a box with lines of width 1, in color @var{color}.
|
|
|
|
@item @code{(:line-width @var{width} :color @var{color} :style @var{style})}
|
|
This way you can explicitly specify all aspects of the box. The value
|
|
@var{width} specifies the width of the lines to draw; it defaults to 1.
|
|
|
|
The value @var{color} specifies the color to draw with. The default is
|
|
the foreground color of the face for simple boxes, and the background
|
|
color of the face for 3D boxes.
|
|
|
|
The value @var{style} specifies whether to draw a 3D box. If it is
|
|
@code{released-button}, the box looks like a 3D button that is not being
|
|
pressed. If it is @code{pressed-button}, the box looks like a 3D button
|
|
that is being pressed. If it is @code{nil} or omitted, a plain 2D box
|
|
is used.
|
|
@end table
|
|
|
|
In older versions of Emacs, before @code{:family}, @code{:height},
|
|
@code{:width}, @code{:weight}, and @code{:slant} existed, these
|
|
attributes were used to specify the type face. They are now
|
|
semi-obsolete, but they still work:
|
|
|
|
@table @code
|
|
@item :font
|
|
This attribute specifies the font name.
|
|
|
|
@item :bold
|
|
A non-@code{nil} value specifies a bold font.
|
|
|
|
@item :italic
|
|
A non-@code{nil} value specifies an italic font.
|
|
@end table
|
|
|
|
For compatibility, you can still set these ``attributes'', even
|
|
though they are not real face attributes. Here is what that does:
|
|
|
|
@table @code
|
|
@item :font
|
|
You can specify an X font name as the ``value'' of this ``attribute'';
|
|
that sets the @code{:family}, @code{:width}, @code{:height},
|
|
@code{:weight}, and @code{:slant} attributes according to the font name.
|
|
|
|
If the value is a pattern with wildcards, the first font that matches
|
|
the pattern is used to set these attributes.
|
|
|
|
@item :bold
|
|
A non-@code{nil} makes the face bold; @code{nil} makes it normal.
|
|
This actually works by setting the @code{:weight} attribute.
|
|
|
|
@item :italic
|
|
A non-@code{nil} makes the face italic; @code{nil} makes it normal.
|
|
This actually works by setting the @code{:slant} attribute.
|
|
@end table
|
|
|
|
@defvar x-bitmap-file-path
|
|
This variable specifies a list of directories for searching
|
|
for bitmap files, for the @code{:stipple} attribute.
|
|
@end defvar
|
|
|
|
@defun bitmap-spec-p object
|
|
This returns @code{t} if @var{object} is a valid bitmap specification,
|
|
suitable for use with @code{:stipple} (see above). It returns
|
|
@code{nil} otherwise.
|
|
@end defun
|
|
|
|
@node Attribute Functions
|
|
@subsection Face Attribute Functions
|
|
|
|
You can modify the attributes of an existing face with the following
|
|
functions. If you specify @var{frame}, they affect just that frame;
|
|
otherwise, they affect all frames as well as the defaults that apply to
|
|
new frames.
|
|
|
|
@tindex set-face-attribute
|
|
@defun set-face-attribute face frame &rest arguments
|
|
This function sets one or more attributes of face @var{face}
|
|
for frame @var{frame}. If @var{frame} is @code{nil}, it sets
|
|
the attribute for all frames, and the defaults for new frames.
|
|
|
|
The extra arguments @var{arguments} specify the attributes to set, and
|
|
the values for them. They should consist of alternating attribute names
|
|
(such as @code{:family} or @code{:underline}) and corresponding values.
|
|
Thus,
|
|
|
|
@example
|
|
(set-face-attribute 'foo nil
|
|
:width 'extended
|
|
:weight 'bold
|
|
:underline "red")
|
|
@end example
|
|
|
|
@noindent
|
|
sets the attributes @code{:width}, @code{:weight} and @code{:underline}
|
|
to the corresponding values.
|
|
@end defun
|
|
|
|
@tindex face-attribute
|
|
@defun face-attribute face attribute &optional frame inherit
|
|
This returns the value of the @var{attribute} attribute of face
|
|
@var{face} on @var{frame}. If @var{frame} is @code{nil},
|
|
that means the selected frame (@pxref{Input Focus}).
|
|
|
|
If @var{frame} is @code{t}, the value is the default for
|
|
@var{face} for new frames.
|
|
|
|
If @var{inherit} is @code{nil}, only attributes directly defined by
|
|
@var{face} are considered, so the return value may be
|
|
@code{unspecified}, or a relative value. If @var{inherit} is
|
|
non-@code{nil}, @var{face}'s definition of @var{attribute} is merged
|
|
with the faces specified by its @code{:inherit} attribute; however the
|
|
return value may still be @code{unspecified} or relative. If
|
|
@var{inherit} is a face or a list of faces, then the result is further
|
|
merged with that face (or faces), until it becomes specified and
|
|
absolute.
|
|
|
|
To ensure that the return value is always specified and absolute, use
|
|
a value of @code{default} for @var{inherit}; this will resolve any
|
|
unspecified or relative values by merging with the @code{default} face
|
|
(which is always completely specified).
|
|
|
|
For example,
|
|
|
|
@example
|
|
(face-attribute 'bold :weight)
|
|
@result{} bold
|
|
@end example
|
|
@end defun
|
|
|
|
The functions above did not exist before Emacs 21. For compatibility
|
|
with older Emacs versions, you can use the following functions to set
|
|
and examine the face attributes which existed in those versions.
|
|
|
|
@tindex face-attribute-relative-p
|
|
@defun face-attribute-relative-p attribute value
|
|
This function returns non-@code{nil} if @var{value}, when used as
|
|
the value of the face attribute @var{attribute}, is relative (that is,
|
|
if it modifies an underlying or inherited value of @var{attribute}).
|
|
@end defun
|
|
|
|
@tindex merge-face-attribute
|
|
@defun merge-face-attribute attribute value1 value2
|
|
If @var{value1} is a relative value for the face attribute
|
|
@var{attribute}, returns it merged with the underlying value
|
|
@var{value2}; otherwise, if @var{value1} is an absolute value for the
|
|
face attribute @var{attribute}, returns @var{value1} unchanged.
|
|
@end defun
|
|
|
|
@defun set-face-foreground face color &optional frame
|
|
@defunx set-face-background face color &optional frame
|
|
These functions set the foreground (or background, respectively) color
|
|
of face @var{face} to @var{color}. The argument @var{color} should be a
|
|
string, the name of a color.
|
|
|
|
Certain shades of gray are implemented by stipple patterns on
|
|
black-and-white screens.
|
|
@end defun
|
|
|
|
@defun set-face-stipple face pattern &optional frame
|
|
This function sets the background stipple pattern of face @var{face}
|
|
to @var{pattern}. The argument @var{pattern} should be the name of a
|
|
stipple pattern defined by the X server, or actual bitmap data
|
|
(@pxref{Face Attributes}), or @code{nil} meaning don't use stipple.
|
|
|
|
Normally there is no need to pay attention to stipple patterns, because
|
|
they are used automatically to handle certain shades of gray.
|
|
@end defun
|
|
|
|
@defun set-face-font face font &optional frame
|
|
This function sets the font of face @var{face}. This actually sets
|
|
the attributes @code{:family}, @code{:width}, @code{:height},
|
|
@code{:weight}, and @code{:slant} according to the font name
|
|
@var{font}.
|
|
@end defun
|
|
|
|
@defun set-face-bold-p face bold-p &optional frame
|
|
This function specifies whether @var{face} should be bold. If
|
|
@var{bold-p} is non-@code{nil}, that means yes; @code{nil} means no.
|
|
This actually sets the @code{:weight} attribute.
|
|
@end defun
|
|
|
|
@defun set-face-italic-p face italic-p &optional frame
|
|
This function specifies whether @var{face} should be italic. If
|
|
@var{italic-p} is non-@code{nil}, that means yes; @code{nil} means no.
|
|
This actually sets the @code{:slant} attribute.
|
|
@end defun
|
|
|
|
@defun set-face-underline-p face underline-p &optional frame
|
|
This function sets the underline attribute of face @var{face}.
|
|
Non-@code{nil} means do underline; @code{nil} means don't.
|
|
@end defun
|
|
|
|
@defun invert-face face &optional frame
|
|
This function inverts the @code{:inverse-video} attribute of face
|
|
@var{face}. If the attribute is @code{nil}, this function sets it to
|
|
@code{t}, and vice versa.
|
|
@end defun
|
|
|
|
These functions examine the attributes of a face. If you don't
|
|
specify @var{frame}, they refer to the default data for new frames.
|
|
They return the symbol @code{unspecified} if the face doesn't define any
|
|
value for that attribute.
|
|
|
|
@defun face-foreground face &optional frame inherit
|
|
@defunx face-background face &optional frame
|
|
These functions return the foreground color (or background color,
|
|
respectively) of face @var{face}, as a string.
|
|
|
|
If @var{inherit} is @code{nil}, only a color directly defined by the face is
|
|
returned. If @var{inherit} is non-@code{nil}, any faces specified by its
|
|
@code{:inherit} attribute are considered as well, and if @var{inherit}
|
|
is a face or a list of faces, then they are also considered, until a
|
|
specified color is found. To ensure that the return value is always
|
|
specified, use a value of @code{default} for @var{inherit}.
|
|
@end defun
|
|
|
|
@defun face-stipple face &optional frame inherit
|
|
This function returns the name of the background stipple pattern of face
|
|
@var{face}, or @code{nil} if it doesn't have one.
|
|
|
|
If @var{inherit} is @code{nil}, only a stipple directly defined by the
|
|
face is returned. If @var{inherit} is non-@code{nil}, any faces
|
|
specified by its @code{:inherit} attribute are considered as well, and
|
|
if @var{inherit} is a face or a list of faces, then they are also
|
|
considered, until a specified stipple is found. To ensure that the
|
|
return value is always specified, use a value of @code{default} for
|
|
@var{inherit}.
|
|
@end defun
|
|
|
|
@defun face-font face &optional frame
|
|
This function returns the name of the font of face @var{face}.
|
|
@end defun
|
|
|
|
@defun face-bold-p face &optional frame
|
|
This function returns @code{t} if @var{face} is bold---that is, if it is
|
|
bolder than normal. It returns @code{nil} otherwise.
|
|
@end defun
|
|
|
|
@defun face-italic-p face &optional frame
|
|
This function returns @code{t} if @var{face} is italic or oblique,
|
|
@code{nil} otherwise.
|
|
@end defun
|
|
|
|
@defun face-underline-p face &optional frame
|
|
This function returns the @code{:underline} attribute of face @var{face}.
|
|
@end defun
|
|
|
|
@defun face-inverse-video-p face &optional frame
|
|
This function returns the @code{:inverse-video} attribute of face @var{face}.
|
|
@end defun
|
|
|
|
@node Displaying Faces
|
|
@subsection Displaying Faces
|
|
|
|
Here are the ways to specify which faces to use for display of text:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
With defaults. The @code{default} face is used as the ultimate
|
|
default for all text. (In Emacs 19 and 20, the @code{default}
|
|
face is used only when no other face is specified.)
|
|
|
|
@item
|
|
For a mode line or header line, the face @code{mode-line} or
|
|
@code{mode-line-inactive}, or @code{header-line}, is merged in just
|
|
before @code{default}.
|
|
|
|
@item
|
|
With text properties. A character can have a @code{face} property; if
|
|
so, the faces and face attributes specified there apply. @xref{Special
|
|
Properties}.
|
|
|
|
If the character has a @code{mouse-face} property, that is used instead
|
|
of the @code{face} property when the mouse is ``near enough'' to the
|
|
character.
|
|
|
|
@item
|
|
With overlays. An overlay can have @code{face} and @code{mouse-face}
|
|
properties too; they apply to all the text covered by the overlay.
|
|
|
|
@item
|
|
With a region that is active. In Transient Mark mode, the region is
|
|
highlighted with the face @code{region} (@pxref{Standard Faces}).
|
|
|
|
@item
|
|
With special glyphs. Each glyph can specify a particular face
|
|
number. @xref{Glyphs}.
|
|
@end itemize
|
|
|
|
If these various sources together specify more than one face for a
|
|
particular character, Emacs merges the attributes of the various faces
|
|
specified. For each attribute, Emacs tries first the face of any
|
|
special glyph; then the face for region highlighting, if appropriate;
|
|
then the faces specified by overlays, followed by those specified by
|
|
text properties, then the @code{mode-line} or
|
|
@code{mode-line-inactive} or @code{header-line} face (if in a mode
|
|
line or a header line), and last the @code{default} face.
|
|
|
|
When multiple overlays cover one character, an overlay with higher
|
|
priority overrides those with lower priority. @xref{Overlays}.
|
|
|
|
@node Font Selection
|
|
@subsection Font Selection
|
|
|
|
@dfn{Selecting a font} means mapping the specified face attributes for
|
|
a character to a font that is available on a particular display. The
|
|
face attributes, as determined by face merging, specify most of the
|
|
font choice, but not all. Part of the choice depends on what character
|
|
it is.
|
|
|
|
If the face specifies a fontset name, that fontset determines a
|
|
pattern for fonts of the given charset. If the face specifies a font
|
|
family, a font pattern is constructed.
|
|
|
|
Emacs tries to find an available font for the given face attributes
|
|
and character's registry and encoding. If there is a font that matches
|
|
exactly, it is used, of course. The hard case is when no available font
|
|
exactly fits the specification. Then Emacs looks for one that is
|
|
``close''---one attribute at a time. You can specify the order to
|
|
consider the attributes. In the case where a specified font family is
|
|
not available, you can specify a set of mappings for alternatives to
|
|
try.
|
|
|
|
@defvar face-font-selection-order
|
|
@tindex face-font-selection-order
|
|
This variable specifies the order of importance of the face attributes
|
|
@code{:width}, @code{:height}, @code{:weight}, and @code{:slant}. The
|
|
value should be a list containing those four symbols, in order of
|
|
decreasing importance.
|
|
|
|
Font selection first finds the best available matches for the first
|
|
attribute listed; then, among the fonts which are best in that way, it
|
|
searches for the best matches in the second attribute, and so on.
|
|
|
|
The attributes @code{:weight} and @code{:width} have symbolic values in
|
|
a range centered around @code{normal}. Matches that are more extreme
|
|
(farther from @code{normal}) are somewhat preferred to matches that are
|
|
less extreme (closer to @code{normal}); this is designed to ensure that
|
|
non-normal faces contrast with normal ones, whenever possible.
|
|
|
|
The default is @code{(:width :height :weight :slant)}, which means first
|
|
find the fonts closest to the specified @code{:width}, then---among the
|
|
fonts with that width---find a best match for the specified font height,
|
|
and so on.
|
|
|
|
One example of a case where this variable makes a difference is when the
|
|
default font has no italic equivalent. With the default ordering, the
|
|
@code{italic} face will use a non-italic font that is similar to the
|
|
default one. But if you put @code{:slant} before @code{:height}, the
|
|
@code{italic} face will use an italic font, even if its height is not
|
|
quite right.
|
|
@end defvar
|
|
|
|
@defvar face-font-family-alternatives
|
|
@tindex face-font-family-alternatives
|
|
This variable lets you specify alternative font families to try, if a
|
|
given family is specified and doesn't exist. Each element should have
|
|
this form:
|
|
|
|
@example
|
|
(@var{family} @var{alternate-families}@dots{})
|
|
@end example
|
|
|
|
If @var{family} is specified but not available, Emacs will try the other
|
|
families given in @var{alternate-families}, one by one, until it finds a
|
|
family that does exist.
|
|
@end defvar
|
|
|
|
@defvar face-font-registry-alternatives
|
|
@tindex face-font-registry-alternatives
|
|
This variable lets you specify alternative font registries to try, if a
|
|
given registry is specified and doesn't exist. Each element should have
|
|
this form:
|
|
|
|
@example
|
|
(@var{registry} @var{alternate-registries}@dots{})
|
|
@end example
|
|
|
|
If @var{registry} is specified but not available, Emacs will try the
|
|
other registries given in @var{alternate-registries}, one by one,
|
|
until it finds a registry that does exist.
|
|
@end defvar
|
|
|
|
Emacs can make use of scalable fonts, but by default it does not use
|
|
them, since the use of too many or too big scalable fonts can crash
|
|
XFree86 servers.
|
|
|
|
@defvar scalable-fonts-allowed
|
|
@tindex scalable-fonts-allowed
|
|
This variable controls which scalable fonts to use. A value of
|
|
@code{nil}, the default, means do not use scalable fonts. @code{t}
|
|
means to use any scalable font that seems appropriate for the text.
|
|
|
|
Otherwise, the value must be a list of regular expressions. Then a
|
|
scalable font is enabled for use if its name matches any regular
|
|
expression in the list. For example,
|
|
|
|
@example
|
|
(setq scalable-fonts-allowed '("muleindian-2$"))
|
|
@end example
|
|
|
|
@noindent
|
|
allows the use of scalable fonts with registry @code{muleindian-2}.
|
|
@end defvar
|
|
|
|
@defun clear-face-cache &optional unload-p
|
|
@tindex clear-face-cache
|
|
This function clears the face cache for all frames.
|
|
If @var{unload-p} is non-@code{nil}, that means to unload
|
|
all unused fonts as well.
|
|
@end defun
|
|
|
|
@defvar face-font-rescale-alist
|
|
This variable specifies scaling for certain faces. Its value should
|
|
be a list of elements of the form
|
|
|
|
@example
|
|
(@var{fontname-regexp} . @var{scale-factor})
|
|
@end example
|
|
|
|
If @var{fontname-regexp} matches the font name that is about to be
|
|
used, this says to choose a larger similar font according to the
|
|
factor @var{scale-factor}. You would use this feature to normalize
|
|
the font size if certain fonts are bigger or smaller than their
|
|
nominal heights and widths would suggest.
|
|
@end defvar
|
|
|
|
@node Face Functions
|
|
@subsection Functions for Working with Faces
|
|
|
|
Here are additional functions for creating and working with faces.
|
|
|
|
@defun make-face name
|
|
This function defines a new face named @var{name}, initially with all
|
|
attributes @code{nil}. It does nothing if there is already a face named
|
|
@var{name}.
|
|
@end defun
|
|
|
|
@defun face-list
|
|
This function returns a list of all defined face names.
|
|
@end defun
|
|
|
|
@defun copy-face old-face new-name &optional frame new-frame
|
|
This function defines a face named @var{new-name} as a copy of the existing
|
|
face named @var{old-face}. It creates the face @var{new-name} if that
|
|
doesn't already exist.
|
|
|
|
If the optional argument @var{frame} is given, this function applies
|
|
only to that frame. Otherwise it applies to each frame individually,
|
|
copying attributes from @var{old-face} in each frame to @var{new-face}
|
|
in the same frame.
|
|
|
|
If the optional argument @var{new-frame} is given, then @code{copy-face}
|
|
copies the attributes of @var{old-face} in @var{frame} to @var{new-name}
|
|
in @var{new-frame}.
|
|
@end defun
|
|
|
|
@defun face-id face
|
|
This function returns the face number of face @var{face}.
|
|
@end defun
|
|
|
|
@defun face-documentation face
|
|
This function returns the documentation string of face @var{face}, or
|
|
@code{nil} if none was specified for it.
|
|
@end defun
|
|
|
|
@defun face-equal face1 face2 &optional frame
|
|
This returns @code{t} if the faces @var{face1} and @var{face2} have the
|
|
same attributes for display.
|
|
@end defun
|
|
|
|
@defun face-differs-from-default-p face &optional frame
|
|
This returns non-@code{nil} if the face @var{face} displays
|
|
differently from the default face.
|
|
@end defun
|
|
|
|
@cindex face alias
|
|
A @dfn{face alias} provides an equivalent name for a face. You can
|
|
define a face alias by giving the alias symbol the @code{face-alias}
|
|
property, with a value of the target face name. The following example
|
|
makes @code{modeline} an alias for the @code{mode-line} face.
|
|
|
|
@example
|
|
(put 'modeline 'face-alias 'mode-line)
|
|
@end example
|
|
|
|
|
|
@node Auto Faces
|
|
@subsection Automatic Face Assignment
|
|
@cindex automatic face assignment
|
|
@cindex faces, automatic choice
|
|
|
|
@cindex Font-Lock mode
|
|
This hook is used for automatically assigning faces to text in the
|
|
buffer. It is part of the implementation of Font-Lock mode.
|
|
|
|
@tindex fontification-functions
|
|
@defvar fontification-functions
|
|
This variable holds a list of functions that are called by Emacs
|
|
redisplay as needed to assign faces automatically to text in the buffer.
|
|
|
|
The functions are called in the order listed, with one argument, a
|
|
buffer position @var{pos}. Each function should attempt to assign faces
|
|
to the text in the current buffer starting at @var{pos}.
|
|
|
|
Each function should record the faces they assign by setting the
|
|
@code{face} property. It should also add a non-@code{nil}
|
|
@code{fontified} property for all the text it has assigned faces to.
|
|
That property tells redisplay that faces have been assigned to that text
|
|
already.
|
|
|
|
It is probably a good idea for each function to do nothing if the
|
|
character after @var{pos} already has a non-@code{nil} @code{fontified}
|
|
property, but this is not required. If one function overrides the
|
|
assignments made by a previous one, the properties as they are
|
|
after the last function finishes are the ones that really matter.
|
|
|
|
For efficiency, we recommend writing these functions so that they
|
|
usually assign faces to around 400 to 600 characters at each call.
|
|
@end defvar
|
|
|
|
@node Font Lookup
|
|
@subsection Looking Up Fonts
|
|
|
|
@defun x-list-fonts pattern &optional face frame maximum
|
|
This function returns a list of available font names that match
|
|
@var{pattern}. If the optional arguments @var{face} and @var{frame} are
|
|
specified, then the list is limited to fonts that are the same size as
|
|
@var{face} currently is on @var{frame}.
|
|
|
|
The argument @var{pattern} should be a string, perhaps with wildcard
|
|
characters: the @samp{*} character matches any substring, and the
|
|
@samp{?} character matches any single character. Pattern matching
|
|
of font names ignores case.
|
|
|
|
If you specify @var{face} and @var{frame}, @var{face} should be a face name
|
|
(a symbol) and @var{frame} should be a frame.
|
|
|
|
The optional argument @var{maximum} sets a limit on how many fonts to
|
|
return. If this is non-@code{nil}, then the return value is truncated
|
|
after the first @var{maximum} matching fonts. Specifying a small value
|
|
for @var{maximum} can make this function much faster, in cases where
|
|
many fonts match the pattern.
|
|
@end defun
|
|
|
|
@defun x-family-fonts &optional family frame
|
|
@tindex x-family-fonts
|
|
This function returns a list describing the available fonts for family
|
|
@var{family} on @var{frame}. If @var{family} is omitted or @code{nil},
|
|
this list applies to all families, and therefore, it contains all
|
|
available fonts. Otherwise, @var{family} must be a string; it may
|
|
contain the wildcards @samp{?} and @samp{*}.
|
|
|
|
The list describes the display that @var{frame} is on; if @var{frame} is
|
|
omitted or @code{nil}, it applies to the selected frame's display
|
|
(@pxref{Input Focus}).
|
|
|
|
The list contains a vector of the following form for each font:
|
|
|
|
@example
|
|
[@var{family} @var{width} @var{point-size} @var{weight} @var{slant}
|
|
@var{fixed-p} @var{full} @var{registry-and-encoding}]
|
|
@end example
|
|
|
|
The first five elements correspond to face attributes; if you
|
|
specify these attributes for a face, it will use this font.
|
|
|
|
The last three elements give additional information about the font.
|
|
@var{fixed-p} is non-@code{nil} if the font is fixed-pitch.
|
|
@var{full} is the full name of the font, and
|
|
@var{registry-and-encoding} is a string giving the registry and
|
|
encoding of the font.
|
|
|
|
The result list is sorted according to the current face font sort order.
|
|
@end defun
|
|
|
|
@defun x-font-family-list &optional frame
|
|
@tindex x-font-family-list
|
|
This function returns a list of the font families available for
|
|
@var{frame}'s display. If @var{frame} is omitted or @code{nil}, it
|
|
describes the selected frame's display (@pxref{Input Focus}).
|
|
|
|
The value is a list of elements of this form:
|
|
|
|
@example
|
|
(@var{family} . @var{fixed-p})
|
|
@end example
|
|
|
|
@noindent
|
|
Here @var{family} is a font family, and @var{fixed-p} is
|
|
non-@code{nil} if fonts of that family are fixed-pitch.
|
|
@end defun
|
|
|
|
@defvar font-list-limit
|
|
@tindex font-list-limit
|
|
This variable specifies maximum number of fonts to consider in font
|
|
matching. The function @code{x-family-fonts} will not return more than
|
|
that many fonts, and font selection will consider only that many fonts
|
|
when searching a matching font for face attributes. The default is
|
|
currently 100.
|
|
@end defvar
|
|
|
|
@node Fontsets
|
|
@subsection Fontsets
|
|
|
|
A @dfn{fontset} is a list of fonts, each assigned to a range of
|
|
character codes. An individual font cannot display the whole range of
|
|
characters that Emacs supports, but a fontset can. Fontsets have names,
|
|
just as fonts do, and you can use a fontset name in place of a font name
|
|
when you specify the ``font'' for a frame or a face. Here is
|
|
information about defining a fontset under Lisp program control.
|
|
|
|
@defun create-fontset-from-fontset-spec fontset-spec &optional style-variant-p noerror
|
|
This function defines a new fontset according to the specification
|
|
string @var{fontset-spec}. The string should have this format:
|
|
|
|
@smallexample
|
|
@var{fontpattern}, @r{[}@var{charsetname}:@var{fontname}@r{]@dots{}}
|
|
@end smallexample
|
|
|
|
@noindent
|
|
Whitespace characters before and after the commas are ignored.
|
|
|
|
The first part of the string, @var{fontpattern}, should have the form of
|
|
a standard X font name, except that the last two fields should be
|
|
@samp{fontset-@var{alias}}.
|
|
|
|
The new fontset has two names, one long and one short. The long name is
|
|
@var{fontpattern} in its entirety. The short name is
|
|
@samp{fontset-@var{alias}}. You can refer to the fontset by either
|
|
name. If a fontset with the same name already exists, an error is
|
|
signaled, unless @var{noerror} is non-@code{nil}, in which case this
|
|
function does nothing.
|
|
|
|
If optional argument @var{style-variant-p} is non-@code{nil}, that says
|
|
to create bold, italic and bold-italic variants of the fontset as well.
|
|
These variant fontsets do not have a short name, only a long one, which
|
|
is made by altering @var{fontpattern} to indicate the bold or italic
|
|
status.
|
|
|
|
The specification string also says which fonts to use in the fontset.
|
|
See below for the details.
|
|
@end defun
|
|
|
|
The construct @samp{@var{charset}:@var{font}} specifies which font to
|
|
use (in this fontset) for one particular character set. Here,
|
|
@var{charset} is the name of a character set, and @var{font} is the font
|
|
to use for that character set. You can use this construct any number of
|
|
times in the specification string.
|
|
|
|
For the remaining character sets, those that you don't specify
|
|
explicitly, Emacs chooses a font based on @var{fontpattern}: it replaces
|
|
@samp{fontset-@var{alias}} with a value that names one character set.
|
|
For the @acronym{ASCII} character set, @samp{fontset-@var{alias}} is replaced
|
|
with @samp{ISO8859-1}.
|
|
|
|
In addition, when several consecutive fields are wildcards, Emacs
|
|
collapses them into a single wildcard. This is to prevent use of
|
|
auto-scaled fonts. Fonts made by scaling larger fonts are not usable
|
|
for editing, and scaling a smaller font is not useful because it is
|
|
better to use the smaller font in its own size, which Emacs does.
|
|
|
|
Thus if @var{fontpattern} is this,
|
|
|
|
@example
|
|
-*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24
|
|
@end example
|
|
|
|
@noindent
|
|
the font specification for @acronym{ASCII} characters would be this:
|
|
|
|
@example
|
|
-*-fixed-medium-r-normal-*-24-*-ISO8859-1
|
|
@end example
|
|
|
|
@noindent
|
|
and the font specification for Chinese GB2312 characters would be this:
|
|
|
|
@example
|
|
-*-fixed-medium-r-normal-*-24-*-gb2312*-*
|
|
@end example
|
|
|
|
You may not have any Chinese font matching the above font
|
|
specification. Most X distributions include only Chinese fonts that
|
|
have @samp{song ti} or @samp{fangsong ti} in the @var{family} field. In
|
|
such a case, @samp{Fontset-@var{n}} can be specified as below:
|
|
|
|
@smallexample
|
|
Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\
|
|
chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-*
|
|
@end smallexample
|
|
|
|
@noindent
|
|
Then, the font specifications for all but Chinese GB2312 characters have
|
|
@samp{fixed} in the @var{family} field, and the font specification for
|
|
Chinese GB2312 characters has a wild card @samp{*} in the @var{family}
|
|
field.
|
|
|
|
@defun set-fontset-font name character fontname &optional frame
|
|
This function modifies the existing fontset @var{name} to
|
|
use the font name @var{fontname} for the character @var{character}.
|
|
|
|
If @var{name} is @code{nil}, this function modifies the default
|
|
fontset, whose short name is @samp{fontset-default}.
|
|
|
|
@var{character} may be a cons; @code{(@var{from} . @var{to})}, where
|
|
@var{from} and @var{to} are non-generic characters. In that case, use
|
|
@var{fontname} for all characters in the range @var{from} and @var{to}
|
|
(inclusive).
|
|
|
|
@var{character} may be a charset. In that case, use
|
|
@var{fontname} for all character in the charsets.
|
|
|
|
@var{fontname} may be a cons; @code{(@var{family} . @var{registry})},
|
|
where @var{family} is a family name of a font (possibly including a
|
|
foundry name at the head), @var{registry} is a registry name of a font
|
|
(possibly including an encoding name at the tail).
|
|
|
|
For instance, this changes the default fontset to use a font of which
|
|
registry name is @samp{JISX0208.1983} for all characters belonging to
|
|
the charset @code{japanese-jisx0208}.
|
|
|
|
@smallexample
|
|
(set-fontset-font nil 'japanese-jisx0208 '(nil . "JISX0208.1983"))
|
|
@end smallexample
|
|
@end defun
|
|
|
|
@defun char-displayable-p char
|
|
This function returns @code{t} if Emacs ought to be able to display
|
|
@var{char}. More precisely, if the selected frame's fontset has a
|
|
font to display the character set that @var{char} belongs to.
|
|
|
|
Fontsets can specify a font on a per-character basis; when the fontset
|
|
does that, this function's value may not be accurate.
|
|
@end defun
|
|
|
|
@node Fringes
|
|
@section Fringes
|
|
@cindex Fringes
|
|
|
|
The @dfn{fringes} of a window are thin vertical strips down the
|
|
sides that are used for displaying bitmaps that indicate truncation,
|
|
continuation, horizontal scrolling, and the overlay arrow.
|
|
|
|
@menu
|
|
* Fringe Size/Pos:: Specifying where to put the window fringes.
|
|
* Fringe Bitmaps:: Displaying bitmaps in the window fringes.
|
|
* Customizing Bitmaps:: Specifying your own bitmaps to use in the fringes.
|
|
* Overlay Arrow:: Display of an arrow to indicate position.
|
|
@end menu
|
|
|
|
@node Fringe Size/Pos
|
|
@subsection Fringe Size and Position
|
|
|
|
Here's how to control the position and width of the window fringes.
|
|
|
|
@defvar fringes-outside-margins
|
|
If the value is non-@code{nil}, the frames appear outside the display
|
|
margins. The fringes normally appear between the display margins and
|
|
the window text. It works to set @code{fringes-outside-margins}
|
|
buffer-locally. @xref{Display Margins}.
|
|
@end defvar
|
|
|
|
@defvar left-fringe-width
|
|
This variable, if non-@code{nil}, specifies the width of the left
|
|
fringe in pixels.
|
|
@end defvar
|
|
|
|
@defvar right-fringe-width
|
|
This variable, if non-@code{nil}, specifies the width of the right
|
|
fringe in pixels.
|
|
@end defvar
|
|
|
|
The values of these variables take effect when you display the
|
|
buffer in a window. If you change them while the buffer is visible,
|
|
you can call @code{set-window-buffer} to display it once again in the
|
|
same window, to make the changes take effect.
|
|
|
|
@defun set-window-fringes window left &optional right outside-margins
|
|
This function sets the fringe widths of window @var{window}.
|
|
If @var{window} is @code{nil}, the selected window is used.
|
|
|
|
The argument @var{left} specifies the width in pixels of the left
|
|
fringe, and likewise @var{right} for the right fringe. A value of
|
|
@code{nil} for either one stands for the default width. If
|
|
@var{outside-margins} is non-@code{nil}, that specifies that fringes
|
|
should appear outside of the display margins.
|
|
@end defun
|
|
|
|
@defun window-fringes &optional window
|
|
This function returns information about the fringes of a window
|
|
@var{window}. If @var{window} is omitted or @code{nil}, the selected
|
|
window is used. The value has the form @code{(@var{left-width}
|
|
@var{right-width} @var{outside-margins})}.
|
|
@end defun
|
|
|
|
@defvar overflow-newline-into-fringe
|
|
If this is non-@code{nil}, lines exactly as wide as the window (not
|
|
counting the final newline character) are not continued. Instead,
|
|
when point is at the end of the line, the cursor appears in the right
|
|
fringe.
|
|
@end defvar
|
|
|
|
@node Fringe Bitmaps
|
|
@subsection Fringe Bitmaps
|
|
@cindex fringe bitmaps
|
|
@cindex bitmaps, fringe
|
|
|
|
The @dfn{fringe bitmaps} are tiny icons Emacs displays in the window
|
|
fringe (on a graphic display) to indicate truncated or continued
|
|
lines, buffer boundaries, overlay arrow, etc. The fringe bitmaps are
|
|
shared by all frames and windows. You can redefine the built-in
|
|
fringe bitmaps, and you can define new fringe bitmaps.
|
|
|
|
The way to display a bitmap in the left or right fringes for a given
|
|
line in a window is by specifying the @code{display} property for one
|
|
of the characters that appears in it. Use a display specification of
|
|
the form @code{(left-fringe @var{bitmap} [@var{face}])} or
|
|
@code{(right-fringe @var{bitmap} [@var{face}])} (@pxref{Display
|
|
Property}). Here, @var{bitmap} is a symbol identifying the bitmap you
|
|
want, and @var{face} (which is optional) is the name of the face whose
|
|
colors should be used for displaying the bitmap, instead of the
|
|
default @code{fringe} face. @var{face} is automatically merged with
|
|
the @code{fringe} face, so normally @var{face} need only specify the
|
|
foreground color for the bitmap.
|
|
|
|
These are the symbols identify the standard fringe bitmaps.
|
|
Evaluate @code{(require 'fringe)} to define them. Fringe bitmap
|
|
symbols have their own name space.
|
|
|
|
@table @asis
|
|
@item Truncation and continuation line bitmaps:
|
|
@code{left-truncation}, @code{right-truncation},
|
|
@code{continued-line}, @code{continuation-line}.
|
|
|
|
@item Buffer indication bitmaps:
|
|
@code{up-arrow}, @code{down-arrow},
|
|
@code{top-left-angle}, @code{top-right-angle},
|
|
@code{bottom-left-angle}, @code{bottom-right-angle},
|
|
@code{left-bracket}, @code{right-bracket}.
|
|
|
|
@item Empty line indication bitmap:
|
|
@code{empty-line}.
|
|
|
|
@item Overlay arrow bitmap:
|
|
@code{overlay-arrow}.
|
|
|
|
@item Bitmaps for displaying the cursor in right fringe:
|
|
@code{filled-box-cursor}, @code{hollow-box-cursor}, @code{hollow-square},
|
|
@code{bar-cursor}, @code{hbar-cursor}.
|
|
@end table
|
|
|
|
@defun fringe-bitmaps-at-pos &optional pos window
|
|
This function returns the fringe bitmaps of the display line
|
|
containing position @var{pos} in window @var{window}. The return
|
|
value has the form @code{(@var{left} @var{right} @var{ov})}, where @var{left}
|
|
is the symbol for the fringe bitmap in the left fringe (or @code{nil}
|
|
if no bitmap), @var{right} is similar for the right fringe, and @var{ov}
|
|
is non-@code{nil} if there is an overlay arrow in the left fringe.
|
|
|
|
The value is @code{nil} if @var{pos} is not visible in @var{window}.
|
|
If @var{window} is @code{nil}, that stands for the selected window.
|
|
If @var{pos} is @code{nil}, that stands for the value of point in
|
|
@var{window}.
|
|
@end defun
|
|
|
|
@node Customizing Bitmaps
|
|
@subsection Customizing Fringe Bitmaps
|
|
|
|
@defun define-fringe-bitmap bitmap bits &optional height width align
|
|
This function defines the symbol @var{bitmap} as a new fringe bitmap,
|
|
or replaces an existing bitmap with that name.
|
|
|
|
The argument @var{bits} specifies the image to use. It should be
|
|
either a string or a vector of integers, where each element (an
|
|
integer) corresponds to one row of the bitmap. Each bit of an integer
|
|
corresponds to one pixel of the bitmap, where the low bit corresponds
|
|
to the rightmost pixel of the bitmap.
|
|
|
|
The height is normally the length of @var{bits}. However, you
|
|
can specify a different height with non-@code{nil} @var{height}. The width
|
|
is normally 8, but you can specify a different width with non-@code{nil}
|
|
@var{width}. The width must be an integer between 1 and 16.
|
|
|
|
The argument @var{align} specifies the positioning of the bitmap
|
|
relative to the range of rows where it is used; the default is to
|
|
center the bitmap. The allowed values are @code{top}, @code{center},
|
|
or @code{bottom}.
|
|
|
|
The @var{align} argument may also be a list @code{(@var{align}
|
|
@var{periodic})} where @var{align} is interpreted as described above.
|
|
If @var{periodic} is non-@code{nil}, it specifies that the rows in
|
|
@code{bits} should be repeated enough times to reach the specified
|
|
height.
|
|
|
|
The return value on success is an integer identifying the new bitmap.
|
|
You should save that integer in a variable so it can be used to select
|
|
this bitmap.
|
|
|
|
This function signals an error if there are no more free bitmap slots.
|
|
@end defun
|
|
|
|
@defun destroy-fringe-bitmap bitmap
|
|
This function destroy the fringe bitmap identified by @var{bitmap}.
|
|
If @var{bitmap} identifies a standard fringe bitmap, it actually
|
|
restores the standard definition of that bitmap, instead of
|
|
eliminating it entirely.
|
|
@end defun
|
|
|
|
@defun set-fringe-bitmap-face bitmap &optional face
|
|
This sets the face for the fringe bitmap @var{bitmap} to @var{face}.
|
|
If @var{face} is @code{nil}, it selects the @code{fringe} face. The
|
|
bitmap's face controls the color to draw it in.
|
|
|
|
@var{face} is merged with the @code{fringe} face, so normally
|
|
@var{face} should specify only the foreground color.
|
|
@end defun
|
|
|
|
@node Overlay Arrow
|
|
@subsection The Overlay Arrow
|
|
@cindex overlay arrow
|
|
|
|
The @dfn{overlay arrow} is useful for directing the user's attention
|
|
to a particular line in a buffer. For example, in the modes used for
|
|
interface to debuggers, the overlay arrow indicates the line of code
|
|
about to be executed. This feature has nothing to do with
|
|
@dfn{overlays} (@pxref{Overlays}).
|
|
|
|
@defvar overlay-arrow-string
|
|
This variable holds the string to display to call attention to a
|
|
particular line, or @code{nil} if the arrow feature is not in use.
|
|
On a graphical display the contents of the string are ignored; instead a
|
|
glyph is displayed in the fringe area to the left of the display area.
|
|
@end defvar
|
|
|
|
@defvar overlay-arrow-position
|
|
This variable holds a marker that indicates where to display the overlay
|
|
arrow. It should point at the beginning of a line. On a non-graphical
|
|
display the arrow text
|
|
appears at the beginning of that line, overlaying any text that would
|
|
otherwise appear. Since the arrow is usually short, and the line
|
|
usually begins with indentation, normally nothing significant is
|
|
overwritten.
|
|
|
|
The overlay string is displayed only in the buffer that this marker
|
|
points into. Thus, only one buffer can have an overlay arrow at any
|
|
given time.
|
|
@c !!! overlay-arrow-position: but the overlay string may remain in the display
|
|
@c of some other buffer until an update is required. This should be fixed
|
|
@c now. Is it?
|
|
@end defvar
|
|
|
|
You can do a similar job by creating an overlay with a
|
|
@code{before-string} property. @xref{Overlay Properties}.
|
|
|
|
You can define multiple overlay arrows via the variable
|
|
@code{overlay-arrow-variable-list}.
|
|
|
|
@defvar overlay-arrow-variable-list
|
|
This variable's value is a list of variables, each of which specifies
|
|
the position of an overlay arrow. The variable
|
|
@code{overlay-arrow-position} has its normal meaning because it is on
|
|
this list.
|
|
@end defvar
|
|
|
|
Each variable on this list can have properties
|
|
@code{overlay-arrow-string} and @code{overlay-arrow-bitmap} that
|
|
specify an overlay arrow string (for text-only terminals) or fringe
|
|
bitmap (for graphical terminals) to display at the corresponding
|
|
overlay arrow position. If either property is not set, the default
|
|
(@code{overlay-arrow-string} or @code{overlay-arrow-fringe-bitmap}) is
|
|
used.
|
|
|
|
@node Scroll Bars
|
|
@section Scroll Bars
|
|
|
|
Normally the frame parameter @code{vertical-scroll-bars} controls
|
|
whether the windows in the frame have vertical scroll bars, and
|
|
whether they are on the left or right. The frame parameter
|
|
@code{scroll-bar-width} specifies how wide they are (@code{nil}
|
|
meaning the default). @xref{Window Frame Parameters}.
|
|
|
|
@defun frame-current-scroll-bars &optional frame
|
|
This function reports the scroll bar type settings for frame
|
|
@var{frame}. The value is a cons cell
|
|
@code{(@var{vertical-type} .@: @var{horizontal-type})}, where
|
|
@var{vertical-type} is either @code{left}, @code{right}, or @code{nil}
|
|
(which means no scroll bar.) @var{horizontal-type} is meant to
|
|
specify the horizontal scroll bar type, but since they are not
|
|
implemented, it is always @code{nil}.
|
|
@end defun
|
|
|
|
@vindex vertical-scroll-bar
|
|
You can enable or disable scroll bars for a particular buffer,
|
|
by setting the variable @code{vertical-scroll-bar}. This variable
|
|
automatically becomes buffer-local when set. The possible values are
|
|
@code{left}, @code{right}, @code{t}, which means to use the
|
|
frame's default, and @code{nil} for no scroll bar.
|
|
|
|
You can also control this for individual windows. Call the function
|
|
@code{set-window-scroll-bars} to specify what to do for a specific window:
|
|
|
|
@defun set-window-scroll-bars window width &optional vertical-type horizontal-type
|
|
This function sets the width and type of scroll bars for window
|
|
@var{window}.
|
|
|
|
@var{width} specifies the scroll bar width in pixels (@code{nil} means
|
|
use the width specified for the frame). @var{vertical-type} specifies
|
|
whether to have a vertical scroll bar and, if so, where. The possible
|
|
values are @code{left}, @code{right} and @code{nil}, just like the
|
|
values of the @code{vertical-scroll-bars} frame parameter.
|
|
|
|
The argument @var{horizontal-type} is meant to specify whether and
|
|
where to have horizontal scroll bars, but since they are not
|
|
implemented, it has no effect. If @var{window} is @code{nil}, the
|
|
selected window is used.
|
|
@end defun
|
|
|
|
@defun window-scroll-bars &optional window
|
|
Report the width and type of scroll bars specified for @var{window}.
|
|
If @var{window} is omitted or @code{nil}, the selected window is used.
|
|
The value is a list of the form @code{(@var{width}
|
|
@var{cols} @var{vertical-type} @var{horizontal-type})}. The value
|
|
@var{width} is the value that was specified for the width (which may
|
|
be @code{nil}); @var{cols} is the number of columns that the scroll
|
|
bar actually occupies.
|
|
|
|
@var{horizontal-type} is not actually meaningful.
|
|
@end defun
|
|
|
|
If you don't specify these values for a window with
|
|
@code{set-window-scroll-bars}, the buffer-local variables
|
|
@code{scroll-bar-mode} and @code{scroll-bar-width} in the buffer being
|
|
displayed control the window's vertical scroll bars. The function
|
|
@code{set-window-buffer} examines these variables. If you change them
|
|
in a buffer that is already visible in a window, you can make the
|
|
window take note of the new values by calling @code{set-window-buffer}
|
|
specifying the same buffer that is already displayed.
|
|
|
|
@defvar scroll-bar-mode
|
|
This variable, always local in all buffers, controls whether and where
|
|
to put scroll bars in windows displaying the buffer. The possible values
|
|
are @code{nil} for no scroll bar, @code{left} to put a scroll bar on
|
|
the left, and @code{right} to put a scroll bar on the right.
|
|
@end defvar
|
|
|
|
@defun window-current-scroll-bars &optional window
|
|
This function reports the scroll bar type for window @var{window}.
|
|
If @var{window} is omitted or @code{nil}, the selected window is used.
|
|
The value is a cons cell
|
|
@code{(@var{vertical-type} .@: @var{horizontal-type})}. Unlike
|
|
@code{window-scroll-bars}, this reports the scroll bar type actually
|
|
used, once frame defaults and @code{scroll-bar-mode} are taken into
|
|
account.
|
|
@end defun
|
|
|
|
@defvar scroll-bar-width
|
|
This variable, always local in all buffers, specifies the width of the
|
|
buffer's scroll bars, measured in pixels. A value of @code{nil} means
|
|
to use the value specified by the frame.
|
|
@end defvar
|
|
|
|
@node Pointer Shape
|
|
@section Pointer Shape
|
|
|
|
Normally, the mouse pointer has the @code{text} shape over text and
|
|
the @code{arrow} shape over window areas which do not correspond to
|
|
any buffer text. You can specify the mouse pointer shape over text or
|
|
images via the @code{pointer} text property, and for images with the
|
|
@code{:pointer} and @code{:map} image properties.
|
|
|
|
The available pointer shapes are: @code{text} (or @code{nil}),
|
|
@code{arrow}, @code{hand}, @code{vdrag}, @code{hdrag},
|
|
@code{modeline}, and @code{hourglass}.
|
|
|
|
@defvar void-text-area-pointer
|
|
@tindex void-text-area-pointer
|
|
This variable specifies the mouse pointer shape in void text areas,
|
|
i.e. the areas after the end of a line or below the last line in the
|
|
buffer. The default is to use the @code{arrow} (non-text) pointer.
|
|
@end defvar
|
|
|
|
@node Display Property
|
|
@section The @code{display} Property
|
|
@cindex display specification
|
|
@kindex display @r{(text property)}
|
|
|
|
The @code{display} text property (or overlay property) is used to
|
|
insert images into text, and also control other aspects of how text
|
|
displays. The value of the @code{display} property should be a
|
|
display specification, or a list or vector containing several display
|
|
specifications.
|
|
|
|
Some kinds of @code{display} properties specify something to display
|
|
instead of the text that has the property. In this case, ``the text''
|
|
means all the consecutive characters that have the same Lisp object as
|
|
their @code{display} property; these characters are replaced as a
|
|
single unit. By contrast, characters that have similar but distinct
|
|
Lisp objects as their @code{display} properties are handled
|
|
separately. Here's a function that illustrates this point:
|
|
|
|
@smallexample
|
|
(defun foo ()
|
|
(goto-char (point-min))
|
|
(dotimes (i 5)
|
|
(let ((string (concat "A")))
|
|
(put-text-property (point) (1+ (point)) 'display string)
|
|
(forward-char 1)
|
|
(put-text-property (point) (1+ (point)) 'display string)
|
|
(forward-char 1))))
|
|
@end smallexample
|
|
|
|
@noindent
|
|
It gives each of the first ten characters in the buffer string
|
|
@code{"A"} as the @code{display} property, but they don't all get the
|
|
same string. The first two characters get the same string, so they
|
|
together are replaced with one @samp{A}. The next two characters get
|
|
a second string, so they together are replaced with one @samp{A}.
|
|
Likewise for each following pair of characters. Thus, the ten
|
|
characters appear as five A's. This function would have the same
|
|
results:
|
|
|
|
@smallexample
|
|
(defun foo ()
|
|
(goto-char (point-min))
|
|
(dotimes (i 5)
|
|
(let ((string (concat "A")))
|
|
(put-text-property (point) (2+ (point)) 'display string)
|
|
(put-text-property (point) (1+ (point)) 'display string)
|
|
(forward-char 2))))
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This illustrates that what matters is the property value for
|
|
each character. If two consecutive characters have the same
|
|
object as the @code{display} property value, it's irrelevant
|
|
whether they got this property from a single call to
|
|
@code{put-text-property} or from two different calls.
|
|
|
|
The rest of this section describes several kinds of
|
|
display specifications and what they mean.
|
|
|
|
@menu
|
|
* Specified Space:: Displaying one space with a specified width.
|
|
* Pixel Specification:: Specifying space width or height in pixels.
|
|
* Other Display Specs:: Displaying an image; magnifying text; moving it
|
|
up or down on the page; adjusting the width
|
|
of spaces within text.
|
|
* Display Margins:: Displaying text or images to the side of the main text.
|
|
@end menu
|
|
|
|
@node Specified Space
|
|
@subsection Specified Spaces
|
|
@cindex spaces, specified height or width
|
|
@cindex specified spaces
|
|
@cindex variable-width spaces
|
|
|
|
To display a space of specified width and/or height, use a display
|
|
specification of the form @code{(space . @var{props})}, where
|
|
@var{props} is a property list (a list of alternating properties and
|
|
values). You can put this property on one or more consecutive
|
|
characters; a space of the specified height and width is displayed in
|
|
place of @emph{all} of those characters. These are the properties you
|
|
can use in @var{props} to specify the weight of the space:
|
|
|
|
@table @code
|
|
@item :width @var{width}
|
|
If @var{width} is an integer or floating point number, it specifies
|
|
that the space width should be @var{width} times the normal character
|
|
width. @var{width} can also be a @dfn{pixel width} specification
|
|
(@pxref{Pixel Specification}).
|
|
|
|
@item :relative-width @var{factor}
|
|
Specifies that the width of the stretch should be computed from the
|
|
first character in the group of consecutive characters that have the
|
|
same @code{display} property. The space width is the width of that
|
|
character, multiplied by @var{factor}.
|
|
|
|
@item :align-to @var{hpos}
|
|
Specifies that the space should be wide enough to reach @var{hpos}.
|
|
If @var{hpos} is a number, it is measured in units of the normal
|
|
character width. @var{hpos} can also be a @dfn{pixel width}
|
|
specification (@pxref{Pixel Specification}).
|
|
@end table
|
|
|
|
You should use one and only one of the above properties. You can
|
|
also specify the height of the space, with these properties:
|
|
|
|
@table @code
|
|
@item :height @var{height}
|
|
Specifies the height of the space.
|
|
If @var{height} is an integer or floating point number, it specifies
|
|
that the space height should be @var{height} times the normal character
|
|
height. The @var{height} may also be a @dfn{pixel height} specification
|
|
(@pxref{Pixel Specification}).
|
|
|
|
@item :relative-height @var{factor}
|
|
Specifies the height of the space, multiplying the ordinary height
|
|
of the text having this display specification by @var{factor}.
|
|
|
|
@item :ascent @var{ascent}
|
|
If the value of @var{ascent} is a non-negative number no greater than
|
|
100, it specifies that @var{ascent} percent of the height of the space
|
|
should be considered as the ascent of the space---that is, the part
|
|
above the baseline. The ascent may also be specified in pixel units
|
|
with a @dfn{pixel ascent} specification (@pxref{Pixel Specification}).
|
|
|
|
@end table
|
|
|
|
Don't use both @code{:height} and @code{:relative-height} together.
|
|
|
|
The @code{:width} and @code{:align-to} properties are supported on
|
|
non-graphic terminals, but the other space properties in this section
|
|
are not.
|
|
|
|
@node Pixel Specification
|
|
@subsection Pixel Specification for Spaces
|
|
@cindex spaces, pixel specification
|
|
|
|
The value of the @code{:width}, @code{:align-to}, @code{:height},
|
|
and @code{:ascent} properties can be a special kind of expression that
|
|
is evaluated during redisplay. The result of the evaluation is used
|
|
as an absolute number of pixels.
|
|
|
|
The following expressions are supported:
|
|
|
|
@smallexample
|
|
@group
|
|
@var{expr} ::= @var{num} | (@var{num}) | @var{unit} | @var{elem} | @var{pos} | @var{image} | @var{form}
|
|
@var{num} ::= @var{integer} | @var{float} | @var{symbol}
|
|
@var{unit} ::= in | mm | cm | width | height
|
|
@end group
|
|
@group
|
|
@var{elem} ::= left-fringe | right-fringe | left-margin | right-margin
|
|
| scroll-bar | text
|
|
@var{pos} ::= left | center | right
|
|
@var{form} ::= (@var{num} . @var{expr}) | (@var{op} @var{expr} ...)
|
|
@var{op} ::= + | -
|
|
@end group
|
|
@end smallexample
|
|
|
|
The form @var{num} specifies a fraction of the default frame font
|
|
height or width. The form @code{(@var{num})} specifies an absolute
|
|
number of pixels. If @var{num} is a symbol, @var{symbol}, its
|
|
buffer-local variable binding is used.
|
|
|
|
The @code{in}, @code{mm}, and @code{cm} units specify the number of
|
|
pixels per inch, millimeter, and centimeter, respectively. The
|
|
@code{width} and @code{height} units correspond to the default width
|
|
and height of the current face. An image specification @code{image}
|
|
corresponds to the width or height of the image.
|
|
|
|
The @code{left-fringe}, @code{right-fringe}, @code{left-margin},
|
|
@code{right-margin}, @code{scroll-bar}, and @code{text} elements
|
|
specify to the width of the corresponding area of the window.
|
|
|
|
The @code{left}, @code{center}, and @code{right} positions can be
|
|
used with @code{:align-to} to specify a position relative to the left
|
|
edge, center, or right edge of the text area.
|
|
|
|
Any of the above window elements (except @code{text}) can also be
|
|
used with @code{:align-to} to specify that the position is relative to
|
|
the left edge of the given area. Once the base offset for a relative
|
|
position has been set (by the first occurrence of one of these
|
|
symbols), further occurrences of these symbols are interpreted as the
|
|
width of the specified area. For example, to align to the center of
|
|
the left-margin, use
|
|
|
|
@example
|
|
:align-to (+ left-margin (0.5 . left-margin))
|
|
@end example
|
|
|
|
If no specific base offset is set for alignment, it is always relative
|
|
to the left edge of the text area. For example, @samp{:align-to 0} in a
|
|
header-line aligns with the first text column in the text area.
|
|
|
|
A value of the form @code{(@var{num} . @var{expr})} stands for the
|
|
product of the values of @var{num} and @var{expr}. For example,
|
|
@code{(2 . in)} specifies a width of 2 inches, while @code{(0.5 .
|
|
@var{image})} specifies half the width (or height) of the specified
|
|
image.
|
|
|
|
The form @code{(+ @var{expr} ...)} adds up the value of the
|
|
expressions. The form @code{(- @var{expr} ...)} negates or subtracts
|
|
the value of the expressions.
|
|
|
|
@node Other Display Specs
|
|
@subsection Other Display Specifications
|
|
|
|
Here are the other sorts of display specifications that you can use
|
|
in the @code{display} text property.
|
|
|
|
@table @code
|
|
@item @var{string}
|
|
Display @var{string} instead of the text that has this property.
|
|
|
|
@item (image . @var{image-props})
|
|
This kind of display specification is an image descriptor (@pxref{Images}).
|
|
When used as a display specification, it means to display the image
|
|
instead of the text that has the display specification.
|
|
|
|
@item (slice @var{x} @var{y} @var{width} @var{height})
|
|
This specification together with @code{image} specifies a @dfn{slice}
|
|
(a partial area) of the image to display. The elements @var{y} and
|
|
@var{x} specify the top left corner of the slice, within the image;
|
|
@var{width} and @var{height} specify the width and height of the
|
|
slice. Integer values are numbers of pixels. A floating point number
|
|
in the range 0.0--1.0 stands for that fraction of the width or height
|
|
of the entire image.
|
|
|
|
@item ((margin nil) @var{string})
|
|
@itemx @var{string}
|
|
A display specification of this form means to display @var{string}
|
|
instead of the text that has the display specification, at the same
|
|
position as that text. This is a special case of marginal display
|
|
(@pxref{Display Margins}).
|
|
|
|
Recursive display specifications are not supported---string display
|
|
specifications must not have @code{display} properties themselves.
|
|
|
|
@item (space-width @var{factor})
|
|
This display specification affects all the space characters within the
|
|
text that has the specification. It displays all of these spaces
|
|
@var{factor} times as wide as normal. The element @var{factor} should
|
|
be an integer or float. Characters other than spaces are not affected
|
|
at all; in particular, this has no effect on tab characters.
|
|
|
|
@item (height @var{height})
|
|
This display specification makes the text taller or shorter.
|
|
Here are the possibilities for @var{height}:
|
|
|
|
@table @asis
|
|
@item @code{(+ @var{n})}
|
|
This means to use a font that is @var{n} steps larger. A ``step'' is
|
|
defined by the set of available fonts---specifically, those that match
|
|
what was otherwise specified for this text, in all attributes except
|
|
height. Each size for which a suitable font is available counts as
|
|
another step. @var{n} should be an integer.
|
|
|
|
@item @code{(- @var{n})}
|
|
This means to use a font that is @var{n} steps smaller.
|
|
|
|
@item a number, @var{factor}
|
|
A number, @var{factor}, means to use a font that is @var{factor} times
|
|
as tall as the default font.
|
|
|
|
@item a symbol, @var{function}
|
|
A symbol is a function to compute the height. It is called with the
|
|
current height as argument, and should return the new height to use.
|
|
|
|
@item anything else, @var{form}
|
|
If the @var{height} value doesn't fit the previous possibilities, it is
|
|
a form. Emacs evaluates it to get the new height, with the symbol
|
|
@code{height} bound to the current specified font height.
|
|
@end table
|
|
|
|
@item (raise @var{factor})
|
|
This kind of display specification raises or lowers the text
|
|
it applies to, relative to the baseline of the line.
|
|
|
|
@var{factor} must be a number, which is interpreted as a multiple of the
|
|
height of the affected text. If it is positive, that means to display
|
|
the characters raised. If it is negative, that means to display them
|
|
lower down.
|
|
|
|
If the text also has a @code{height} display specification, that does
|
|
not affect the amount of raising or lowering, which is based on the
|
|
faces used for the text.
|
|
@end table
|
|
|
|
You can make any display specification conditional. To do that,
|
|
package it in another list of the form @code{(when @var{condition} .
|
|
@var{spec})}. Then the specification @var{spec} applies only when
|
|
@var{condition} evaluates to a non-@code{nil} value. During the
|
|
evaluation, @code{object} is bound to the string or buffer having the
|
|
conditional @code{display} property. @code{position} and
|
|
@code{buffer-position} are bound to the position within @code{object}
|
|
and the buffer position where the @code{display} property was found,
|
|
respectively. Both positions can be different when @code{object} is a
|
|
string.
|
|
|
|
@node Display Margins
|
|
@subsection Displaying in the Margins
|
|
@cindex display margins
|
|
@cindex margins, display
|
|
|
|
A buffer can have blank areas called @dfn{display margins} on the left
|
|
and on the right. Ordinary text never appears in these areas, but you
|
|
can put things into the display margins using the @code{display}
|
|
property.
|
|
|
|
To put text in the left or right display margin of the window, use a
|
|
display specification of the form @code{(margin right-margin)} or
|
|
@code{(margin left-margin)} on it. To put an image in a display margin,
|
|
use that display specification along with the display specification for
|
|
the image. Unfortunately, there is currently no way to make
|
|
text or images in the margin mouse-sensitive.
|
|
|
|
If you put such a display specification directly on text in the
|
|
buffer, the specified margin display appears @emph{instead of} that
|
|
buffer text itself. To put something in the margin @emph{in
|
|
association with} certain buffer text without preventing or altering
|
|
the display of that text, put a @code{before-string} property on the
|
|
text and put the display specification on the contents of the
|
|
before-string.
|
|
|
|
Before the display margins can display anything, you must give
|
|
them a nonzero width. The usual way to do that is to set these
|
|
variables:
|
|
|
|
@defvar left-margin-width
|
|
@tindex left-margin-width
|
|
This variable specifies the width of the left margin.
|
|
It is buffer-local in all buffers.
|
|
@end defvar
|
|
|
|
@defvar right-margin-width
|
|
@tindex right-margin-width
|
|
This variable specifies the width of the right margin.
|
|
It is buffer-local in all buffers.
|
|
@end defvar
|
|
|
|
Setting these variables does not immediately affect the window. These
|
|
variables are checked when a new buffer is displayed in the window.
|
|
Thus, you can make changes take effect by calling
|
|
@code{set-window-buffer}.
|
|
|
|
You can also set the margin widths immediately.
|
|
|
|
@defun set-window-margins window left &optional right
|
|
@tindex set-window-margins
|
|
This function specifies the margin widths for window @var{window}.
|
|
The argument @var{left} controls the left margin and
|
|
@var{right} controls the right margin (default @code{0}).
|
|
@end defun
|
|
|
|
@defun window-margins &optional window
|
|
@tindex window-margins
|
|
This function returns the left and right margins of @var{window}
|
|
as a cons cell of the form @code{(@var{left} . @var{right})}.
|
|
If @var{window} is @code{nil}, the selected window is used.
|
|
@end defun
|
|
|
|
@node Images
|
|
@section Images
|
|
@cindex images in buffers
|
|
|
|
To display an image in an Emacs buffer, you must first create an image
|
|
descriptor, then use it as a display specifier in the @code{display}
|
|
property of text that is displayed (@pxref{Display Property}).
|
|
|
|
Emacs can display a number of different image formats; some of them
|
|
are supported only if particular support libraries are installed on
|
|
your machine. In some environments, Emacs can load image
|
|
libraries on demand; if so, the variable @code{image-library-alist}
|
|
can be used to modify the set of known names for these dynamic
|
|
libraries (though it is not possible to add new image formats).
|
|
|
|
The supported image formats include XBM, XPM (this requires the
|
|
libraries @code{libXpm} version 3.4k and @code{libz}), GIF (requiring
|
|
@code{libungif} 4.1.0), Postscript, PBM, JPEG (requiring the
|
|
@code{libjpeg} library version v6a), TIFF (requiring @code{libtiff}
|
|
v3.4), and PNG (requiring @code{libpng} 1.0.2).
|
|
|
|
You specify one of these formats with an image type symbol. The image
|
|
type symbols are @code{xbm}, @code{xpm}, @code{gif}, @code{postscript},
|
|
@code{pbm}, @code{jpeg}, @code{tiff}, and @code{png}.
|
|
|
|
@defvar image-types
|
|
This variable contains a list of those image type symbols that are
|
|
potentially supported in the current configuration.
|
|
@emph{Potentially} here means that Emacs knows about the image types,
|
|
not necessarily that they can be loaded (they could depend on
|
|
unavailable dynamic libraries, for example).
|
|
|
|
To know which image types are really available, use
|
|
@code{image-type-available-p}.
|
|
@end defvar
|
|
|
|
@defvar image-library-alist
|
|
This in an alist of image types vs external libraries needed to
|
|
display them.
|
|
|
|
Each element is a list @code{(@var{image-type} @var{library}...)},
|
|
where the car is a supported image format from @code{image-types}, and
|
|
the rest are strings giving alternate filenames for the corresponding
|
|
external libraries to load.
|
|
|
|
Emacs tries to load the libraries in the order they appear on the
|
|
list; if none is loaded, the running session of Emacs won't support
|
|
the image type. @code{pbm} and @code{xbm} don't need to be listed;
|
|
they're always supported.
|
|
|
|
This variable is ignored if the image libraries are statically linked
|
|
into Emacs.
|
|
@end defvar
|
|
|
|
@defun image-type-available-p type
|
|
@findex image-type-available-p
|
|
|
|
This function returns non-@code{nil} if image type @var{type} is
|
|
available, i.e., if images of this type can be loaded and displayed in
|
|
Emacs. @var{type} should be one of the types contained in
|
|
@code{image-types}.
|
|
|
|
For image types whose support libraries are statically linked, this
|
|
function always returns @code{t}; for other image types, it returns
|
|
@code{t} if the dynamic library could be loaded, @code{nil} otherwise.
|
|
@end defun
|
|
|
|
@menu
|
|
* Image Descriptors:: How to specify an image for use in @code{:display}.
|
|
* XBM Images:: Special features for XBM format.
|
|
* XPM Images:: Special features for XPM format.
|
|
* GIF Images:: Special features for GIF format.
|
|
* Postscript Images:: Special features for Postscript format.
|
|
* Other Image Types:: Various other formats are supported.
|
|
* Defining Images:: Convenient ways to define an image for later use.
|
|
* Showing Images:: Convenient ways to display an image once it is defined.
|
|
* Image Cache:: Internal mechanisms of image display.
|
|
@end menu
|
|
|
|
@node Image Descriptors
|
|
@subsection Image Descriptors
|
|
@cindex image descriptor
|
|
|
|
An image description is a list of the form @code{(image
|
|
. @var{props})}, where @var{props} is a property list containing
|
|
alternating keyword symbols (symbols whose names start with a colon) and
|
|
their values. You can use any Lisp object as a property, but the only
|
|
properties that have any special meaning are certain symbols, all of
|
|
them keywords.
|
|
|
|
Every image descriptor must contain the property @code{:type
|
|
@var{type}} to specify the format of the image. The value of @var{type}
|
|
should be an image type symbol; for example, @code{xpm} for an image in
|
|
XPM format.
|
|
|
|
Here is a list of other properties that are meaningful for all image
|
|
types:
|
|
|
|
@table @code
|
|
@item :file @var{file}
|
|
The @code{:file} property says to load the image from file
|
|
@var{file}. If @var{file} is not an absolute file name, it is expanded
|
|
in @code{data-directory}.
|
|
|
|
@item :data @var{data}
|
|
The @code{:data} property says the actual contents of the image.
|
|
Each image must use either @code{:data} or @code{:file}, but not both.
|
|
For most image types, the value of the @code{:data} property should be a
|
|
string containing the image data; we recommend using a unibyte string.
|
|
|
|
Before using @code{:data}, look for further information in the section
|
|
below describing the specific image format. For some image types,
|
|
@code{:data} may not be supported; for some, it allows other data types;
|
|
for some, @code{:data} alone is not enough, so you need to use other
|
|
image properties along with @code{:data}.
|
|
|
|
@item :margin @var{margin}
|
|
The @code{:margin} property specifies how many pixels to add as an
|
|
extra margin around the image. The value, @var{margin}, must be a
|
|
non-negative number, or a pair @code{(@var{x} . @var{y})} of such
|
|
numbers. If it is a pair, @var{x} specifies how many pixels to add
|
|
horizontally, and @var{y} specifies how many pixels to add vertically.
|
|
If @code{:margin} is not specified, the default is zero.
|
|
|
|
@item :ascent @var{ascent}
|
|
The @code{:ascent} property specifies the amount of the image's
|
|
height to use for its ascent---that is, the part above the baseline.
|
|
The value, @var{ascent}, must be a number in the range 0 to 100, or
|
|
the symbol @code{center}.
|
|
|
|
If @var{ascent} is a number, that percentage of the image's height is
|
|
used for its ascent.
|
|
|
|
If @var{ascent} is @code{center}, the image is vertically centered
|
|
around a centerline which would be the vertical centerline of text drawn
|
|
at the position of the image, in the manner specified by the text
|
|
properties and overlays that apply to the image.
|
|
|
|
If this property is omitted, it defaults to 50.
|
|
|
|
@item :relief @var{relief}
|
|
The @code{:relief} property, if non-@code{nil}, adds a shadow rectangle
|
|
around the image. The value, @var{relief}, specifies the width of the
|
|
shadow lines, in pixels. If @var{relief} is negative, shadows are drawn
|
|
so that the image appears as a pressed button; otherwise, it appears as
|
|
an unpressed button.
|
|
|
|
@item :conversion @var{algorithm}
|
|
The @code{:conversion} property, if non-@code{nil}, specifies a
|
|
conversion algorithm that should be applied to the image before it is
|
|
displayed; the value, @var{algorithm}, specifies which algorithm.
|
|
|
|
@table @code
|
|
@item laplace
|
|
@itemx emboss
|
|
Specifies the Laplace edge detection algorithm, which blurs out small
|
|
differences in color while highlighting larger differences. People
|
|
sometimes consider this useful for displaying the image for a
|
|
``disabled'' button.
|
|
|
|
@item (edge-detection :matrix @var{matrix} :color-adjust @var{adjust})
|
|
Specifies a general edge-detection algorithm. @var{matrix} must be
|
|
either a nine-element list or a nine-element vector of numbers. A pixel
|
|
at position @math{x/y} in the transformed image is computed from
|
|
original pixels around that position. @var{matrix} specifies, for each
|
|
pixel in the neighborhood of @math{x/y}, a factor with which that pixel
|
|
will influence the transformed pixel; element @math{0} specifies the
|
|
factor for the pixel at @math{x-1/y-1}, element @math{1} the factor for
|
|
the pixel at @math{x/y-1} etc., as shown below:
|
|
@iftex
|
|
@tex
|
|
$$\pmatrix{x-1/y-1 & x/y-1 & x+1/y-1 \cr
|
|
x-1/y & x/y & x+1/y \cr
|
|
x-1/y+1& x/y+1 & x+1/y+1 \cr}$$
|
|
@end tex
|
|
@end iftex
|
|
@ifnottex
|
|
@display
|
|
(x-1/y-1 x/y-1 x+1/y-1
|
|
x-1/y x/y x+1/y
|
|
x-1/y+1 x/y+1 x+1/y+1)
|
|
@end display
|
|
@end ifnottex
|
|
|
|
The resulting pixel is computed from the color intensity of the color
|
|
resulting from summing up the RGB values of surrounding pixels,
|
|
multiplied by the specified factors, and dividing that sum by the sum
|
|
of the factors' absolute values.
|
|
|
|
Laplace edge-detection currently uses a matrix of
|
|
@iftex
|
|
@tex
|
|
$$\pmatrix{1 & 0 & 0 \cr
|
|
0& 0 & 0 \cr
|
|
9 & 9 & -1 \cr}$$
|
|
@end tex
|
|
@end iftex
|
|
@ifnottex
|
|
@display
|
|
(1 0 0
|
|
0 0 0
|
|
9 9 -1)
|
|
@end display
|
|
@end ifnottex
|
|
|
|
Emboss edge-detection uses a matrix of
|
|
@iftex
|
|
@tex
|
|
$$\pmatrix{ 2 & -1 & 0 \cr
|
|
-1 & 0 & 1 \cr
|
|
0 & 1 & -2 \cr}$$
|
|
@end tex
|
|
@end iftex
|
|
@ifnottex
|
|
@display
|
|
( 2 -1 0
|
|
-1 0 1
|
|
0 1 -2)
|
|
@end display
|
|
@end ifnottex
|
|
|
|
@item disabled
|
|
Specifies transforming the image so that it looks ``disabled''.
|
|
@end table
|
|
|
|
@item :mask @var{mask}
|
|
If @var{mask} is @code{heuristic} or @code{(heuristic @var{bg})}, build
|
|
a clipping mask for the image, so that the background of a frame is
|
|
visible behind the image. If @var{bg} is not specified, or if @var{bg}
|
|
is @code{t}, determine the background color of the image by looking at
|
|
the four corners of the image, assuming the most frequently occurring
|
|
color from the corners is the background color of the image. Otherwise,
|
|
@var{bg} must be a list @code{(@var{red} @var{green} @var{blue})}
|
|
specifying the color to assume for the background of the image.
|
|
|
|
If @var{mask} is @code{nil}, remove a mask from the image, if it has
|
|
one. Images in some formats include a mask which can be removed by
|
|
specifying @code{:mask nil}.
|
|
|
|
@item :pointer @var{shape}
|
|
This specifies the pointer shape when the mouse pointer is over this
|
|
image. @xref{Pointer Shape}, for available pointer shapes.
|
|
|
|
@item :map @var{map}
|
|
This associates an image map of @dfn{hot spots} with this image.
|
|
|
|
An image map is an alist where each element has the format
|
|
@code{(@var{area} @var{id} @var{plist})}. An @var{area} is specified
|
|
as either a rectangle, a circle, or a polygon.
|
|
|
|
A rectangle is a cons
|
|
@code{(rect . ((@var{x0} . @var{y0}) . (@var{x1} . @var{y1})))}
|
|
which specifies the pixel coordinates of the upper left and bottom right
|
|
corners of the rectangle area.
|
|
|
|
A circle is a cons
|
|
@code{(circle . ((@var{x0} . @var{y0}) . @var{r}))}
|
|
which specifies the center and the radius of the circle; @var{r} may
|
|
be a float or integer.
|
|
|
|
A polygon is a cons
|
|
@code{(poly . [@var{x0} @var{y0} @var{x1} @var{y1} ...])}
|
|
where each pair in the vector describes one corner in the polygon.
|
|
|
|
When the mouse pointer is above a hot-spot area of an image, the
|
|
@var{plist} of that hot-spot is consulted; if it contains a @code{help-echo}
|
|
property it defines a tool-tip for the hot-spot, and if it contains
|
|
a @code{pointer} property, it defines the shape of the mouse cursor when
|
|
it is over the hot-spot.
|
|
@xref{Pointer Shape}, for available pointer shapes.
|
|
|
|
When you click the mouse when the mouse pointer is over a hot-spot, an
|
|
event is composed by combining the @var{id} of the hot-spot with the
|
|
mouse event; for instance, @code{[area4 mouse-1]} if the hot-spot's
|
|
@var{id} is @code{area4}.
|
|
@end table
|
|
|
|
@defun image-mask-p spec &optional frame
|
|
@tindex image-mask-p
|
|
This function returns @code{t} if image @var{spec} has a mask bitmap.
|
|
@var{frame} is the frame on which the image will be displayed.
|
|
@var{frame} @code{nil} or omitted means to use the selected frame
|
|
(@pxref{Input Focus}).
|
|
@end defun
|
|
|
|
@node XBM Images
|
|
@subsection XBM Images
|
|
@cindex XBM
|
|
|
|
To use XBM format, specify @code{xbm} as the image type. This image
|
|
format doesn't require an external library, so images of this type are
|
|
always supported.
|
|
|
|
Additional image properties supported for the @code{xbm} image type are:
|
|
|
|
@table @code
|
|
@item :foreground @var{foreground}
|
|
The value, @var{foreground}, should be a string specifying the image
|
|
foreground color, or @code{nil} for the default color. This color is
|
|
used for each pixel in the XBM that is 1. The default is the frame's
|
|
foreground color.
|
|
|
|
@item :background @var{background}
|
|
The value, @var{background}, should be a string specifying the image
|
|
background color, or @code{nil} for the default color. This color is
|
|
used for each pixel in the XBM that is 0. The default is the frame's
|
|
background color.
|
|
@end table
|
|
|
|
If you specify an XBM image using data within Emacs instead of an
|
|
external file, use the following three properties:
|
|
|
|
@table @code
|
|
@item :data @var{data}
|
|
The value, @var{data}, specifies the contents of the image.
|
|
There are three formats you can use for @var{data}:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
A vector of strings or bool-vectors, each specifying one line of the
|
|
image. Do specify @code{:height} and @code{:width}.
|
|
|
|
@item
|
|
A string containing the same byte sequence as an XBM file would contain.
|
|
You must not specify @code{:height} and @code{:width} in this case,
|
|
because omitting them is what indicates the data has the format of an
|
|
XBM file. The file contents specify the height and width of the image.
|
|
|
|
@item
|
|
A string or a bool-vector containing the bits of the image (plus perhaps
|
|
some extra bits at the end that will not be used). It should contain at
|
|
least @var{width} * @code{height} bits. In this case, you must specify
|
|
@code{:height} and @code{:width}, both to indicate that the string
|
|
contains just the bits rather than a whole XBM file, and to specify the
|
|
size of the image.
|
|
@end itemize
|
|
|
|
@item :width @var{width}
|
|
The value, @var{width}, specifies the width of the image, in pixels.
|
|
|
|
@item :height @var{height}
|
|
The value, @var{height}, specifies the height of the image, in pixels.
|
|
@end table
|
|
|
|
@node XPM Images
|
|
@subsection XPM Images
|
|
@cindex XPM
|
|
|
|
To use XPM format, specify @code{xpm} as the image type. The
|
|
additional image property @code{:color-symbols} is also meaningful with
|
|
the @code{xpm} image type:
|
|
|
|
@table @code
|
|
@item :color-symbols @var{symbols}
|
|
The value, @var{symbols}, should be an alist whose elements have the
|
|
form @code{(@var{name} . @var{color})}. In each element, @var{name} is
|
|
the name of a color as it appears in the image file, and @var{color}
|
|
specifies the actual color to use for displaying that name.
|
|
@end table
|
|
|
|
@node GIF Images
|
|
@subsection GIF Images
|
|
@cindex GIF
|
|
|
|
For GIF images, specify image type @code{gif}.
|
|
|
|
@table @code
|
|
@item :index @var{index}
|
|
You can use @code{:index} to specify one image from a GIF file that
|
|
contains more than one image. This property specifies use of image
|
|
number @var{index} from the file. If the GIF file doesn't contain an
|
|
image with index @var{index}, the image displays as a hollow box.
|
|
@end table
|
|
|
|
@ignore
|
|
This could be used to implement limited support for animated GIFs.
|
|
For example, the following function displays a multi-image GIF file
|
|
at point-min in the current buffer, switching between sub-images
|
|
every 0.1 seconds.
|
|
|
|
(defun show-anim (file max)
|
|
"Display multi-image GIF file FILE which contains MAX subimages."
|
|
(display-anim (current-buffer) file 0 max t))
|
|
|
|
(defun display-anim (buffer file idx max first-time)
|
|
(when (= idx max)
|
|
(setq idx 0))
|
|
(let ((img (create-image file nil :image idx)))
|
|
(save-excursion
|
|
(set-buffer buffer)
|
|
(goto-char (point-min))
|
|
(unless first-time (delete-char 1))
|
|
(insert-image img))
|
|
(run-with-timer 0.1 nil 'display-anim buffer file (1+ idx) max nil)))
|
|
@end ignore
|
|
|
|
@node Postscript Images
|
|
@subsection Postscript Images
|
|
@cindex Postscript images
|
|
|
|
To use Postscript for an image, specify image type @code{postscript}.
|
|
This works only if you have Ghostscript installed. You must always use
|
|
these three properties:
|
|
|
|
@table @code
|
|
@item :pt-width @var{width}
|
|
The value, @var{width}, specifies the width of the image measured in
|
|
points (1/72 inch). @var{width} must be an integer.
|
|
|
|
@item :pt-height @var{height}
|
|
The value, @var{height}, specifies the height of the image in points
|
|
(1/72 inch). @var{height} must be an integer.
|
|
|
|
@item :bounding-box @var{box}
|
|
The value, @var{box}, must be a list or vector of four integers, which
|
|
specifying the bounding box of the Postscript image, analogous to the
|
|
@samp{BoundingBox} comment found in Postscript files.
|
|
|
|
@example
|
|
%%BoundingBox: 22 171 567 738
|
|
@end example
|
|
@end table
|
|
|
|
Displaying Postscript images from Lisp data is not currently
|
|
implemented, but it may be implemented by the time you read this.
|
|
See the @file{etc/NEWS} file to make sure.
|
|
|
|
@node Other Image Types
|
|
@subsection Other Image Types
|
|
@cindex PBM
|
|
|
|
For PBM images, specify image type @code{pbm}. Color, gray-scale and
|
|
monochromatic images are supported. For mono PBM images, two additional
|
|
image properties are supported.
|
|
|
|
@table @code
|
|
@item :foreground @var{foreground}
|
|
The value, @var{foreground}, should be a string specifying the image
|
|
foreground color, or @code{nil} for the default color. This color is
|
|
used for each pixel in the XBM that is 1. The default is the frame's
|
|
foreground color.
|
|
|
|
@item :background @var{background}
|
|
The value, @var{background}, should be a string specifying the image
|
|
background color, or @code{nil} for the default color. This color is
|
|
used for each pixel in the XBM that is 0. The default is the frame's
|
|
background color.
|
|
@end table
|
|
|
|
For JPEG images, specify image type @code{jpeg}.
|
|
|
|
For TIFF images, specify image type @code{tiff}.
|
|
|
|
For PNG images, specify image type @code{png}.
|
|
|
|
@node Defining Images
|
|
@subsection Defining Images
|
|
|
|
The functions @code{create-image}, @code{defimage} and
|
|
@code{find-image} provide convenient ways to create image descriptors.
|
|
|
|
@defun create-image file-or-data &optional type data-p &rest props
|
|
@tindex create-image
|
|
This function creates and returns an image descriptor which uses the
|
|
data in @var{file-or-data}. @var{file-or-data} can be a file name or
|
|
a string containing the image data; @var{data-p} should be @code{nil}
|
|
for the former case, non-@code{nil} for the latter case.
|
|
|
|
The optional argument @var{type} is a symbol specifying the image type.
|
|
If @var{type} is omitted or @code{nil}, @code{create-image} tries to
|
|
determine the image type from the file's first few bytes, or else
|
|
from the file's name.
|
|
|
|
The remaining arguments, @var{props}, specify additional image
|
|
properties---for example,
|
|
|
|
@example
|
|
(create-image "foo.xpm" 'xpm nil :heuristic-mask t)
|
|
@end example
|
|
|
|
The function returns @code{nil} if images of this type are not
|
|
supported. Otherwise it returns an image descriptor.
|
|
@end defun
|
|
|
|
@defmac defimage symbol specs &optional doc
|
|
@tindex defimage
|
|
This macro defines @var{symbol} as an image name. The arguments
|
|
@var{specs} is a list which specifies how to display the image.
|
|
The third argument, @var{doc}, is an optional documentation string.
|
|
|
|
Each argument in @var{specs} has the form of a property list, and each
|
|
one should specify at least the @code{:type} property and either the
|
|
@code{:file} or the @code{:data} property. The value of @code{:type}
|
|
should be a symbol specifying the image type, the value of
|
|
@code{:file} is the file to load the image from, and the value of
|
|
@code{:data} is a string containing the actual image data. Here is an
|
|
example:
|
|
|
|
@example
|
|
(defimage test-image
|
|
((:type xpm :file "~/test1.xpm")
|
|
(:type xbm :file "~/test1.xbm")))
|
|
@end example
|
|
|
|
@code{defimage} tests each argument, one by one, to see if it is
|
|
usable---that is, if the type is supported and the file exists. The
|
|
first usable argument is used to make an image descriptor which is
|
|
stored in @var{symbol}.
|
|
|
|
If none of the alternatives will work, then @var{symbol} is defined
|
|
as @code{nil}.
|
|
@end defmac
|
|
|
|
@defun find-image specs
|
|
@tindex find-image
|
|
This function provides a convenient way to find an image satisfying one
|
|
of a list of image specifications @var{specs}.
|
|
|
|
Each specification in @var{specs} is a property list with contents
|
|
depending on image type. All specifications must at least contain the
|
|
properties @code{:type @var{type}} and either @w{@code{:file @var{file}}}
|
|
or @w{@code{:data @var{DATA}}}, where @var{type} is a symbol specifying
|
|
the image type, e.g.@: @code{xbm}, @var{file} is the file to load the
|
|
image from, and @var{data} is a string containing the actual image data.
|
|
The first specification in the list whose @var{type} is supported, and
|
|
@var{file} exists, is used to construct the image specification to be
|
|
returned. If no specification is satisfied, @code{nil} is returned.
|
|
|
|
The image is looked for first on @code{load-path} and then in
|
|
@code{data-directory}.
|
|
@end defun
|
|
|
|
@node Showing Images
|
|
@subsection Showing Images
|
|
|
|
You can use an image descriptor by setting up the @code{display}
|
|
property yourself, but it is easier to use the functions in this
|
|
section.
|
|
|
|
@defun insert-image image &optional string area slice
|
|
This function inserts @var{image} in the current buffer at point. The
|
|
value @var{image} should be an image descriptor; it could be a value
|
|
returned by @code{create-image}, or the value of a symbol defined with
|
|
@code{defimage}. The argument @var{string} specifies the text to put
|
|
in the buffer to hold the image. If it is omitted or @code{nil},
|
|
@code{insert-image} uses @code{" "} by default.
|
|
|
|
The argument @var{area} specifies whether to put the image in a margin.
|
|
If it is @code{left-margin}, the image appears in the left margin;
|
|
@code{right-margin} specifies the right margin. If @var{area} is
|
|
@code{nil} or omitted, the image is displayed at point within the
|
|
buffer's text.
|
|
|
|
The argument @var{slice} specifies a slice of the image to insert. If
|
|
@var{slice} is @code{nil} or omitted the whole image is inserted.
|
|
Otherwise, @var{slice} is a list @code{(@var{x} @var{y} @var{width}
|
|
@var{height})} which specifies the @var{x} and @var{y} positions and
|
|
@var{width} and @var{height} of the image area to insert. Integer
|
|
values are in units of pixels. A floating point number in the range
|
|
0.0--1.0 stands for that fraction of the width or height of the entire
|
|
image.
|
|
|
|
Internally, this function inserts @var{string} in the buffer, and gives
|
|
it a @code{display} property which specifies @var{image}. @xref{Display
|
|
Property}.
|
|
@end defun
|
|
|
|
@defun insert-sliced-image image &optional string area rows cols
|
|
This function inserts @var{image} in the current buffer at point, like
|
|
@code{insert-image}, but splits the image into @var{rows}x@var{cols}
|
|
equally sized slices.
|
|
@end defun
|
|
|
|
@defun put-image image pos &optional string area
|
|
This function puts image @var{image} in front of @var{pos} in the
|
|
current buffer. The argument @var{pos} should be an integer or a
|
|
marker. It specifies the buffer position where the image should appear.
|
|
The argument @var{string} specifies the text that should hold the image
|
|
as an alternative to the default.
|
|
|
|
The argument @var{image} must be an image descriptor, perhaps returned
|
|
by @code{create-image} or stored by @code{defimage}.
|
|
|
|
The argument @var{area} specifies whether to put the image in a margin.
|
|
If it is @code{left-margin}, the image appears in the left margin;
|
|
@code{right-margin} specifies the right margin. If @var{area} is
|
|
@code{nil} or omitted, the image is displayed at point within the
|
|
buffer's text.
|
|
|
|
Internally, this function creates an overlay, and gives it a
|
|
@code{before-string} property containing text that has a @code{display}
|
|
property whose value is the image. (Whew!)
|
|
@end defun
|
|
|
|
@defun remove-images start end &optional buffer
|
|
This function removes images in @var{buffer} between positions
|
|
@var{start} and @var{end}. If @var{buffer} is omitted or @code{nil},
|
|
images are removed from the current buffer.
|
|
|
|
This removes only images that were put into @var{buffer} the way
|
|
@code{put-image} does it, not images that were inserted with
|
|
@code{insert-image} or in other ways.
|
|
@end defun
|
|
|
|
@defun image-size spec &optional pixels frame
|
|
@tindex image-size
|
|
This function returns the size of an image as a pair
|
|
@w{@code{(@var{width} . @var{height})}}. @var{spec} is an image
|
|
specification. @var{pixels} non-@code{nil} means return sizes
|
|
measured in pixels, otherwise return sizes measured in canonical
|
|
character units (fractions of the width/height of the frame's default
|
|
font). @var{frame} is the frame on which the image will be displayed.
|
|
@var{frame} null or omitted means use the selected frame (@pxref{Input
|
|
Focus}).
|
|
@end defun
|
|
|
|
@node Image Cache
|
|
@subsection Image Cache
|
|
|
|
Emacs stores images in an image cache when it displays them, so it can
|
|
display them again more efficiently. It removes an image from the cache
|
|
when it hasn't been displayed for a specified period of time.
|
|
|
|
When an image is looked up in the cache, its specification is compared
|
|
with cached image specifications using @code{equal}. This means that
|
|
all images with equal specifications share the same image in the cache.
|
|
|
|
@defvar image-cache-eviction-delay
|
|
@tindex image-cache-eviction-delay
|
|
This variable specifies the number of seconds an image can remain in the
|
|
cache without being displayed. When an image is not displayed for this
|
|
length of time, Emacs removes it from the image cache.
|
|
|
|
If the value is @code{nil}, Emacs does not remove images from the cache
|
|
except when you explicitly clear it. This mode can be useful for
|
|
debugging.
|
|
@end defvar
|
|
|
|
@defun clear-image-cache &optional frame
|
|
@tindex clear-image-cache
|
|
This function clears the image cache. If @var{frame} is non-@code{nil},
|
|
only the cache for that frame is cleared. Otherwise all frames' caches
|
|
are cleared.
|
|
@end defun
|
|
|
|
@node Buttons
|
|
@section Buttons
|
|
@cindex buttons
|
|
@cindex buttons in buffers
|
|
@cindex clickable buttons in buffers
|
|
|
|
The @emph{button} package defines functions for inserting and
|
|
manipulating clickable (with the mouse, or via keyboard commands)
|
|
buttons in Emacs buffers, such as might be used for help hyper-links,
|
|
etc. Emacs uses buttons for the hyper-links in help text and the like.
|
|
|
|
A button is essentially a set of properties attached (via text
|
|
properties or overlays) to a region of text in an Emacs buffer. These
|
|
properties are called @dfn{button properties}.
|
|
|
|
One of the these properties (@code{action}) is a function, which will
|
|
be called when the user invokes it using the keyboard or the mouse.
|
|
The invoked function may then examine the button and use its other
|
|
properties as desired.
|
|
|
|
In some ways the Emacs button package duplicates functionality offered
|
|
by the widget package (@pxref{Top, , Introduction, widget, The Emacs
|
|
Widget Library}), but the button package has the advantage that it is
|
|
much faster, much smaller, and much simpler to use (for elisp
|
|
programmers---for users, the result is about the same). The extra
|
|
speed and space savings are useful mainly if you need to create many
|
|
buttons in a buffer (for instance an @code{*Apropos*} buffer uses
|
|
buttons to make entries clickable, and may contain many thousands of
|
|
entries).
|
|
|
|
@menu
|
|
* Button Properties:: Button properties with special meanings.
|
|
* Button Types:: Defining common properties for classes of buttons.
|
|
* Making Buttons:: Adding buttons to Emacs buffers.
|
|
* Manipulating Buttons:: Getting and setting properties of buttons.
|
|
* Button Buffer Commands:: Buffer-wide commands and bindings for buttons.
|
|
@end menu
|
|
|
|
@node Button Properties
|
|
@subsection Button Properties
|
|
@cindex button properties
|
|
|
|
Buttons have an associated list of properties defining their
|
|
appearance and behavior, and other arbitrary properties may be used
|
|
for application specific purposes. Some properties that have special
|
|
meaning to the button package include:
|
|
|
|
@table @code
|
|
@item action
|
|
@kindex action @r{(button property)}
|
|
The function to call when the user invokes the button, which is passed
|
|
the single argument @var{button}. By default this is @code{ignore},
|
|
which does nothing.
|
|
|
|
@item mouse-action
|
|
@kindex mouse-action @r{(button property)}
|
|
This is similar to @code{action}, and when present, will be used
|
|
instead of @code{action} for button invocations resulting from
|
|
mouse-clicks (instead of the user hitting @key{RET}). If not
|
|
present, mouse-clicks use @code{action} instead.
|
|
|
|
@item face
|
|
@kindex face @r{(button property)}
|
|
This is an Emacs face controlling how buttons of this type are
|
|
displayed; by default this is the @code{button} face.
|
|
|
|
@item mouse-face
|
|
@kindex mouse-face @r{(button property)}
|
|
This is an additional face which controls appearance during
|
|
mouse-overs (merged with the usual button face); by default this is
|
|
the usual Emacs @code{highlight} face.
|
|
|
|
@item keymap
|
|
@kindex keymap @r{(button property)}
|
|
The button's keymap, defining bindings active within the button
|
|
region. By default this is the usual button region keymap, stored
|
|
in the variable @code{button-map}, which defines @key{RET} and
|
|
@key{mouse-2} to invoke the button.
|
|
|
|
@item type
|
|
@kindex type @r{(button property)}
|
|
The button-type of the button. When creating a button, this is
|
|
usually specified using the @code{:type} keyword argument.
|
|
@xref{Button Types}.
|
|
|
|
@item help-echo
|
|
@kindex help-index @r{(button property)}
|
|
A string displayed by the Emacs tool-tip help system; by default,
|
|
@code{"mouse-2, RET: Push this button"}.
|
|
|
|
@item follow-link
|
|
@kindex follow-link @r{(button property)}
|
|
The follow-link property, defining how a @key{Mouse-1} click behaves
|
|
on this button, @xref{Links and Mouse-1}.
|
|
|
|
@item button
|
|
@kindex button @r{(button property)}
|
|
All buttons have a non-@code{nil} @code{button} property, which may be useful
|
|
in finding regions of text that comprise buttons (which is what the
|
|
standard button functions do).
|
|
@end table
|
|
|
|
There are other properties defined for the regions of text in a
|
|
button, but these are not generally interesting for typical uses.
|
|
|
|
@node Button Types
|
|
@subsection Button Types
|
|
@cindex button types
|
|
|
|
Every button has a button @emph{type}, which defines default values
|
|
for the button's properties. Button types are arranged in a
|
|
hierarchy, with specialized types inheriting from more general types,
|
|
so that it's easy to define special-purpose types of buttons for
|
|
specific tasks.
|
|
|
|
@defun define-button-type name &rest properties
|
|
@tindex define-button-type
|
|
Define a `button type' called @var{name}. The remaining arguments
|
|
form a sequence of @var{property value} pairs, specifying default
|
|
property values for buttons with this type (a button's type may be set
|
|
by giving it a @code{type} property when creating the button, using
|
|
the @code{:type} keyword argument).
|
|
|
|
In addition, the keyword argument @code{:supertype} may be used to
|
|
specify a button-type from which @var{name} inherits its default
|
|
property values. Note that this inheritance happens only when
|
|
@var{name} is defined; subsequent changes to a supertype are not
|
|
reflected in its subtypes.
|
|
@end defun
|
|
|
|
Using @code{define-button-type} to define default properties for
|
|
buttons is not necessary---buttons without any specified type use the
|
|
built-in button-type @code{button}---but it is encouraged, since
|
|
doing so usually makes the resulting code clearer and more efficient.
|
|
|
|
@node Making Buttons
|
|
@subsection Making Buttons
|
|
@cindex making buttons
|
|
|
|
Buttons are associated with a region of text, using an overlay or
|
|
text properties to hold button-specific information, all of which are
|
|
initialized from the button's type (which defaults to the built-in
|
|
button type @code{button}). Like all Emacs text, the appearance of
|
|
the button is governed by the @code{face} property; by default (via
|
|
the @code{face} property inherited from the @code{button} button-type)
|
|
this is a simple underline, like a typical web-page link.
|
|
|
|
For convenience, there are two sorts of button-creation functions,
|
|
those that add button properties to an existing region of a buffer,
|
|
called @code{make-...button}, and those also insert the button text,
|
|
called @code{insert-...button}.
|
|
|
|
The button-creation functions all take the @code{&rest} argument
|
|
@var{properties}, which should be a sequence of @var{property value}
|
|
pairs, specifying properties to add to the button; see @ref{Button
|
|
Properties}. In addition, the keyword argument @code{:type} may be
|
|
used to specify a button-type from which to inherit other properties;
|
|
see @ref{Button Types}. Any properties not explicitly specified
|
|
during creation will be inherited from the button's type (if the type
|
|
defines such a property).
|
|
|
|
The following functions add a button using an overlay
|
|
(@pxref{Overlays}) to hold the button properties:
|
|
|
|
@defun make-button beg end &rest properties
|
|
@tindex make-button
|
|
This makes a button from @var{beg} to @var{end} in the
|
|
current buffer, and returns it.
|
|
@end defun
|
|
|
|
@defun insert-button label &rest properties
|
|
@tindex insert-button
|
|
This insert a button with the label @var{label} at point,
|
|
and returns it.
|
|
@end defun
|
|
|
|
The following functions are similar, but use Emacs text properties
|
|
(@pxref{Text Properties}) to hold the button properties, making the
|
|
button actually part of the text instead of being a property of the
|
|
buffer. Buttons using text properties do not create markers into the
|
|
buffer, which is important for speed when you use extremely large
|
|
numbers of buttons. Both functions return the position of the start
|
|
of the new button:
|
|
|
|
@defun make-text-button beg end &rest properties
|
|
@tindex make-text-button
|
|
This makes a button from @var{beg} to @var{end} in the current buffer, using
|
|
text properties.
|
|
@end defun
|
|
|
|
@defun insert-text-button label &rest properties
|
|
@tindex insert-text-button
|
|
This inserts a button with the label @var{label} at point, using text
|
|
properties.
|
|
@end defun
|
|
|
|
@node Manipulating Buttons
|
|
@subsection Manipulating Buttons
|
|
@cindex manipulating buttons
|
|
|
|
These are functions for getting and setting properties of buttons.
|
|
Often these are used by a button's invocation function to determine
|
|
what to do.
|
|
|
|
Where a @var{button} parameter is specified, it means an object
|
|
referring to a specific button, either an overlay (for overlay
|
|
buttons), or a buffer-position or marker (for text property buttons).
|
|
Such an object is passed as the first argument to a button's
|
|
invocation function when it is invoked.
|
|
|
|
@defun button-start button
|
|
@tindex button-start
|
|
Return the position at which @var{button} starts.
|
|
@end defun
|
|
|
|
@defun button-end button
|
|
@tindex button-end
|
|
Return the position at which @var{button} ends.
|
|
@end defun
|
|
|
|
@defun button-get button prop
|
|
@tindex button-get
|
|
Get the property of button @var{button} named @var{prop}.
|
|
@end defun
|
|
|
|
@defun button-put button prop val
|
|
@tindex button-put
|
|
Set @var{button}'s @var{prop} property to @var{val}.
|
|
@end defun
|
|
|
|
@defun button-activate button &optional use-mouse-action
|
|
@tindex button-activate
|
|
Call @var{button}'s @code{action} property (i.e., invoke it). If
|
|
@var{use-mouse-action} is non-@code{nil}, try to invoke the button's
|
|
@code{mouse-action} property instead of @code{action}; if the button
|
|
has no @code{mouse-action} property, use @code{action} as normal.
|
|
@end defun
|
|
|
|
@defun button-label button
|
|
@tindex button-label
|
|
Return @var{button}'s text label.
|
|
@end defun
|
|
|
|
@defun button-type button
|
|
@tindex button-type
|
|
Return @var{button}'s button-type.
|
|
@end defun
|
|
|
|
@defun button-has-type-p button type
|
|
@tindex button-has-type-p
|
|
Return @code{t} if @var{button} has button-type @var{type}, or one of
|
|
@var{type}'s subtypes.
|
|
@end defun
|
|
|
|
@defun button-at pos
|
|
@tindex button-at
|
|
Return the button at position @var{pos} in the current buffer, or @code{nil}.
|
|
@end defun
|
|
|
|
@defun button-type-put type prop val
|
|
@tindex button-type-put
|
|
Set the button-type @var{type}'s @var{prop} property to @var{val}.
|
|
@end defun
|
|
|
|
@defun button-type-get type prop
|
|
@tindex button-type-get
|
|
Get the property of button-type @var{type} named @var{prop}.
|
|
@end defun
|
|
|
|
@defun button-type-subtype-p type supertype
|
|
@tindex button-type-subtype-p
|
|
Return @code{t} if button-type @var{type} is a subtype of @var{supertype}.
|
|
@end defun
|
|
|
|
@node Button Buffer Commands
|
|
@subsection Button Buffer Commands
|
|
@cindex button buffer commands
|
|
|
|
These are commands and functions for locating and operating on
|
|
buttons in an Emacs buffer.
|
|
|
|
@code{push-button} is the command that a user uses to actually `push'
|
|
a button, and is bound by default in the button itself to @key{RET}
|
|
and to @key{mouse-2} using a region-specific keymap. Commands
|
|
that are useful outside the buttons itself, such as
|
|
@code{forward-button} and @code{backward-button} are additionally
|
|
available in the keymap stored in @code{button-buffer-map}; a mode
|
|
which uses buttons may want to use @code{button-buffer-map} as a
|
|
parent keymap for its keymap.
|
|
|
|
If the button has a non-@code{nil} @code{follow-link} property, and
|
|
@var{mouse-1-click-follows-link} is set, a quick @key{Mouse-1} click
|
|
will also activate the @code{push-button} command.
|
|
@xref{Links and Mouse-1}.
|
|
|
|
@deffn Command push-button &optional pos use-mouse-action
|
|
@tindex push-button
|
|
Perform the action specified by a button at location @var{pos}.
|
|
@var{pos} may be either a buffer position or a mouse-event. If
|
|
@var{use-mouse-action} is non-@code{nil}, or @var{pos} is a
|
|
mouse-event (@pxref{Mouse Events}), try to invoke the button's
|
|
@code{mouse-action} property instead of @code{action}; if the button
|
|
has no @code{mouse-action} property, use @code{action} as normal.
|
|
@var{pos} defaults to point, except when @code{push-button} is invoked
|
|
interactively as the result of a mouse-event, in which case, the mouse
|
|
event's position is used. If there's no button at @var{pos}, do
|
|
nothing and return @code{nil}, otherwise return @code{t}.
|
|
@end deffn
|
|
|
|
@deffn Command forward-button n &optional wrap display-message
|
|
@tindex forward-button
|
|
Move to the @var{n}th next button, or @var{n}th previous button if
|
|
@var{n} is negative. If @var{n} is zero, move to the start of any
|
|
button at point. If @var{wrap} is non-@code{nil}, moving past either
|
|
end of the buffer continues from the other end. If
|
|
@var{display-message} is non-@code{nil}, the button's help-echo string
|
|
is displayed. Any button with a non-@code{nil} @code{skip} property
|
|
is skipped over. Returns the button found.
|
|
@end deffn
|
|
|
|
@deffn Command backward-button n &optional wrap display-message
|
|
@tindex backward-button
|
|
Move to the @var{n}th previous button, or @var{n}th next button if
|
|
@var{n} is negative. If @var{n} is zero, move to the start of any
|
|
button at point. If @var{wrap} is non-@code{nil}, moving past either
|
|
end of the buffer continues from the other end. If
|
|
@var{display-message} is non-@code{nil}, the button's help-echo string
|
|
is displayed. Any button with a non-@code{nil} @code{skip} property
|
|
is skipped over. Returns the button found.
|
|
@end deffn
|
|
|
|
@defun next-button pos &optional count-current
|
|
@tindex next-button
|
|
Return the next button after position @var{pos} in the current buffer.
|
|
If @var{count-current} is non-@code{nil}, count any button at
|
|
@var{pos} in the search, instead of starting at the next button.
|
|
@end defun
|
|
|
|
@defun previous-button pos &optional count-current
|
|
@tindex previous-button
|
|
Return the @var{n}th button before position @var{pos} in the current
|
|
buffer. If @var{count-current} is non-@code{nil}, count any button at
|
|
@var{pos} in the search, instead of starting at the next button.
|
|
@end defun
|
|
|
|
@node Blinking
|
|
@section Blinking Parentheses
|
|
@cindex parenthesis matching
|
|
@cindex blinking
|
|
@cindex balancing parentheses
|
|
@cindex close parenthesis
|
|
|
|
This section describes the mechanism by which Emacs shows a matching
|
|
open parenthesis when the user inserts a close parenthesis.
|
|
|
|
@defvar blink-paren-function
|
|
The value of this variable should be a function (of no arguments) to
|
|
be called whenever a character with close parenthesis syntax is inserted.
|
|
The value of @code{blink-paren-function} may be @code{nil}, in which
|
|
case nothing is done.
|
|
@end defvar
|
|
|
|
@defopt blink-matching-paren
|
|
If this variable is @code{nil}, then @code{blink-matching-open} does
|
|
nothing.
|
|
@end defopt
|
|
|
|
@defopt blink-matching-paren-distance
|
|
This variable specifies the maximum distance to scan for a matching
|
|
parenthesis before giving up.
|
|
@end defopt
|
|
|
|
@defopt blink-matching-delay
|
|
This variable specifies the number of seconds for the cursor to remain
|
|
at the matching parenthesis. A fraction of a second often gives
|
|
good results, but the default is 1, which works on all systems.
|
|
@end defopt
|
|
|
|
@deffn Command blink-matching-open
|
|
This function is the default value of @code{blink-paren-function}. It
|
|
assumes that point follows a character with close parenthesis syntax and
|
|
moves the cursor momentarily to the matching opening character. If that
|
|
character is not already on the screen, it displays the character's
|
|
context in the echo area. To avoid long delays, this function does not
|
|
search farther than @code{blink-matching-paren-distance} characters.
|
|
|
|
Here is an example of calling this function explicitly.
|
|
|
|
@smallexample
|
|
@group
|
|
(defun interactive-blink-matching-open ()
|
|
@c Do not break this line! -- rms.
|
|
@c The first line of a doc string
|
|
@c must stand alone.
|
|
"Indicate momentarily the start of sexp before point."
|
|
(interactive)
|
|
@end group
|
|
@group
|
|
(let ((blink-matching-paren-distance
|
|
(buffer-size))
|
|
(blink-matching-paren t))
|
|
(blink-matching-open)))
|
|
@end group
|
|
@end smallexample
|
|
@end deffn
|
|
|
|
@node Inverse Video
|
|
@section Inverse Video
|
|
@cindex Inverse Video
|
|
|
|
@defopt inverse-video
|
|
@cindex highlighting
|
|
This variable controls whether Emacs uses inverse video for all text
|
|
on the screen. Non-@code{nil} means yes, @code{nil} means no. The
|
|
default is @code{nil}.
|
|
@end defopt
|
|
|
|
@defopt mode-line-inverse-video
|
|
This variable controls the use of inverse video for mode lines and
|
|
menu bars. If it is non-@code{nil}, then these lines are displayed in
|
|
the face @code{mode-line}. Otherwise, these lines are displayed
|
|
normally, just like other text. The default is @code{t}.
|
|
@end defopt
|
|
|
|
@node Usual Display
|
|
@section Usual Display Conventions
|
|
|
|
The usual display conventions define how to display each character
|
|
code. You can override these conventions by setting up a display table
|
|
(@pxref{Display Tables}). Here are the usual display conventions:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Character codes 32 through 126 map to glyph codes 32 through 126.
|
|
Normally this means they display as themselves.
|
|
|
|
@item
|
|
Character code 9 is a horizontal tab. It displays as whitespace
|
|
up to a position determined by @code{tab-width}.
|
|
|
|
@item
|
|
Character code 10 is a newline.
|
|
|
|
@item
|
|
All other codes in the range 0 through 31, and code 127, display in one
|
|
of two ways according to the value of @code{ctl-arrow}. If it is
|
|
non-@code{nil}, these codes map to sequences of two glyphs, where the
|
|
first glyph is the @acronym{ASCII} code for @samp{^}. (A display table can
|
|
specify a glyph to use instead of @samp{^}.) Otherwise, these codes map
|
|
just like the codes in the range 128 to 255.
|
|
|
|
On MS-DOS terminals, Emacs arranges by default for the character code
|
|
127 to be mapped to the glyph code 127, which normally displays as an
|
|
empty polygon. This glyph is used to display non-@acronym{ASCII} characters
|
|
that the MS-DOS terminal doesn't support. @xref{MS-DOS and MULE,,,
|
|
emacs, The GNU Emacs Manual}.
|
|
|
|
@item
|
|
Character codes 128 through 255 map to sequences of four glyphs, where
|
|
the first glyph is the @acronym{ASCII} code for @samp{\}, and the others are
|
|
digit characters representing the character code in octal. (A display
|
|
table can specify a glyph to use instead of @samp{\}.)
|
|
|
|
@item
|
|
Multibyte character codes above 256 are displayed as themselves, or as a
|
|
question mark or empty box if the terminal cannot display that
|
|
character.
|
|
@end itemize
|
|
|
|
The usual display conventions apply even when there is a display
|
|
table, for any character whose entry in the active display table is
|
|
@code{nil}. Thus, when you set up a display table, you need only
|
|
specify the characters for which you want special behavior.
|
|
|
|
These display rules apply to carriage return (character code 13), when
|
|
it appears in the buffer. But that character may not appear in the
|
|
buffer where you expect it, if it was eliminated as part of end-of-line
|
|
conversion (@pxref{Coding System Basics}).
|
|
|
|
These variables affect the way certain characters are displayed on the
|
|
screen. Since they change the number of columns the characters occupy,
|
|
they also affect the indentation functions. These variables also affect
|
|
how the mode line is displayed; if you want to force redisplay of the
|
|
mode line using the new values, call the function
|
|
@code{force-mode-line-update} (@pxref{Mode Line Format}).
|
|
|
|
@defopt ctl-arrow
|
|
@cindex control characters in display
|
|
This buffer-local variable controls how control characters are
|
|
displayed. If it is non-@code{nil}, they are displayed as a caret
|
|
followed by the character: @samp{^A}. If it is @code{nil}, they are
|
|
displayed as a backslash followed by three octal digits: @samp{\001}.
|
|
@end defopt
|
|
|
|
@c Following may have overfull hbox.
|
|
@defvar default-ctl-arrow
|
|
The value of this variable is the default value for @code{ctl-arrow} in
|
|
buffers that do not override it. @xref{Default Value}.
|
|
@end defvar
|
|
|
|
@defopt tab-width
|
|
The value of this variable is the spacing between tab stops used for
|
|
displaying tab characters in Emacs buffers. The value is in units of
|
|
columns, and the default is 8. Note that this feature is completely
|
|
independent of the user-settable tab stops used by the command
|
|
@code{tab-to-tab-stop}. @xref{Indent Tabs}.
|
|
@end defopt
|
|
|
|
@defopt indicate-empty-lines
|
|
@tindex indicate-empty-lines
|
|
@cindex fringes, and empty line indication
|
|
When this is non-@code{nil}, Emacs displays a special glyph in the
|
|
fringe of each empty line at the end of the buffer, on terminals that
|
|
support it (window systems). @xref{Fringes}.
|
|
@end defopt
|
|
|
|
@defvar indicate-buffer-boundaries
|
|
This buffer-local variable controls how the buffer boundaries and
|
|
window scrolling are indicated in the window fringes.
|
|
|
|
Emacs can indicate the buffer boundaries---that is, the first and last
|
|
line in the buffer---with angle icons when they appear on the screen.
|
|
In addition, Emacs can display an up-arrow in the fringe to show
|
|
that there is text above the screen, and a down-arrow to show
|
|
there is text below the screen.
|
|
|
|
There are four kinds of basic values:
|
|
|
|
@table @asis
|
|
@item @code{nil}
|
|
Don't display the icons.
|
|
@item @code{left}
|
|
Display them in the left fringe.
|
|
@item @code{right}
|
|
Display them in the right fringe.
|
|
@item @var{anything-else}
|
|
Display the icon at the top of the window top in the left fringe, and other
|
|
in the right fringe.
|
|
@end table
|
|
|
|
If value is a cons @code{(@var{angles} . @var{arrows})}, @var{angles}
|
|
controls the angle icons, and @var{arrows} controls the arrows. Both
|
|
@var{angles} and @var{arrows} work according to the table above.
|
|
Thus, @code{(t . right)} places the top angle icon in the left
|
|
fringe, the bottom angle icon in the right fringe, and both arrows in
|
|
the right fringe.
|
|
@end defvar
|
|
|
|
@defvar default-indicate-buffer-boundaries
|
|
The value of this variable is the default value for
|
|
@code{indicate-buffer-boundaries} in buffers that do not override it.
|
|
@end defvar
|
|
|
|
@node Display Tables
|
|
@section Display Tables
|
|
|
|
@cindex display table
|
|
You can use the @dfn{display table} feature to control how all possible
|
|
character codes display on the screen. This is useful for displaying
|
|
European languages that have letters not in the @acronym{ASCII} character
|
|
set.
|
|
|
|
The display table maps each character code into a sequence of
|
|
@dfn{glyphs}, each glyph being a graphic that takes up one character
|
|
position on the screen. You can also define how to display each glyph
|
|
on your terminal, using the @dfn{glyph table}.
|
|
|
|
Display tables affect how the mode line is displayed; if you want to
|
|
force redisplay of the mode line using a new display table, call
|
|
@code{force-mode-line-update} (@pxref{Mode Line Format}).
|
|
|
|
@menu
|
|
* Display Table Format:: What a display table consists of.
|
|
* Active Display Table:: How Emacs selects a display table to use.
|
|
* Glyphs:: How to define a glyph, and what glyphs mean.
|
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@end menu
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@node Display Table Format
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@subsection Display Table Format
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A display table is actually a char-table (@pxref{Char-Tables}) with
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@code{display-table} as its subtype.
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@defun make-display-table
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This creates and returns a display table. The table initially has
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@code{nil} in all elements.
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@end defun
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The ordinary elements of the display table are indexed by character
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codes; the element at index @var{c} says how to display the character
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code @var{c}. The value should be @code{nil} or a vector of glyph
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values (@pxref{Glyphs}). If an element is @code{nil}, it says to
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display that character according to the usual display conventions
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(@pxref{Usual Display}).
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If you use the display table to change the display of newline
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characters, the whole buffer will be displayed as one long ``line.''
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The display table also has six ``extra slots'' which serve special
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purposes. Here is a table of their meanings; @code{nil} in any slot
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means to use the default for that slot, as stated below.
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@table @asis
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@item 0
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The glyph for the end of a truncated screen line (the default for this
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is @samp{$}). @xref{Glyphs}. On graphical terminals, Emacs uses
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arrows in the fringes to indicate truncation, so the display table has
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no effect.
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@item 1
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The glyph for the end of a continued line (the default is @samp{\}).
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On graphical terminals, Emacs uses curved arrows in the fringes to
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indicate continuation, so the display table has no effect.
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@item 2
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The glyph for indicating a character displayed as an octal character
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code (the default is @samp{\}).
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@item 3
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The glyph for indicating a control character (the default is @samp{^}).
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@item 4
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A vector of glyphs for indicating the presence of invisible lines (the
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default is @samp{...}). @xref{Selective Display}.
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@item 5
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The glyph used to draw the border between side-by-side windows (the
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default is @samp{|}). @xref{Splitting Windows}. This takes effect only
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when there are no scroll bars; if scroll bars are supported and in use,
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a scroll bar separates the two windows.
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@end table
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For example, here is how to construct a display table that mimics the
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effect of setting @code{ctl-arrow} to a non-@code{nil} value:
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@example
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(setq disptab (make-display-table))
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(let ((i 0))
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(while (< i 32)
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(or (= i ?\t) (= i ?\n)
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(aset disptab i (vector ?^ (+ i 64))))
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(setq i (1+ i)))
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(aset disptab 127 (vector ?^ ??)))
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@end example
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@defun display-table-slot display-table slot
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This function returns the value of the extra slot @var{slot} of
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@var{display-table}. The argument @var{slot} may be a number from 0 to
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5 inclusive, or a slot name (symbol). Valid symbols are
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@code{truncation}, @code{wrap}, @code{escape}, @code{control},
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@code{selective-display}, and @code{vertical-border}.
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@end defun
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@defun set-display-table-slot display-table slot value
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This function stores @var{value} in the extra slot @var{slot} of
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@var{display-table}. The argument @var{slot} may be a number from 0 to
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5 inclusive, or a slot name (symbol). Valid symbols are
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@code{truncation}, @code{wrap}, @code{escape}, @code{control},
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@code{selective-display}, and @code{vertical-border}.
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@end defun
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@defun describe-display-table display-table
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@tindex describe-display-table
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This function displays a description of the display table
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@var{display-table} in a help buffer.
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@end defun
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@deffn Command describe-current-display-table
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@tindex describe-current-display-table
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This command displays a description of the current display table in a
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help buffer.
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@end deffn
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@node Active Display Table
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@subsection Active Display Table
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@cindex active display table
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Each window can specify a display table, and so can each buffer. When
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a buffer @var{b} is displayed in window @var{w}, display uses the
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display table for window @var{w} if it has one; otherwise, the display
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table for buffer @var{b} if it has one; otherwise, the standard display
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table if any. The display table chosen is called the @dfn{active}
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display table.
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@defun window-display-table &optional window
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This function returns @var{window}'s display table, or @code{nil}
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if @var{window} does not have an assigned display table. The default
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for @var{window} is the selected window.
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@end defun
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@defun set-window-display-table window table
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This function sets the display table of @var{window} to @var{table}.
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The argument @var{table} should be either a display table or
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@code{nil}.
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@end defun
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@defvar buffer-display-table
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This variable is automatically buffer-local in all buffers; its value in
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a particular buffer specifies the display table for that buffer. If it
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is @code{nil}, that means the buffer does not have an assigned display
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table.
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@end defvar
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@defvar standard-display-table
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This variable's value is the default display table, used whenever a
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window has no display table and neither does the buffer displayed in
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that window. This variable is @code{nil} by default.
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@end defvar
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If there is no display table to use for a particular window---that is,
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if the window specifies none, its buffer specifies none, and
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@code{standard-display-table} is @code{nil}---then Emacs uses the usual
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display conventions for all character codes in that window. @xref{Usual
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Display}.
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A number of functions for changing the standard display table
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are defined in the library @file{disp-table}.
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@node Glyphs
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@subsection Glyphs
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@cindex glyph
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A @dfn{glyph} is a generalization of a character; it stands for an
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image that takes up a single character position on the screen. Glyphs
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are represented in Lisp as integers, just as characters are. Normally
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Emacs finds glyphs in the display table (@pxref{Display Tables}).
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A glyph can be @dfn{simple} or it can be defined by the @dfn{glyph
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table}. A simple glyph is just a way of specifying a character and a
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face to output it in. The glyph code for a simple glyph, mod 524288,
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is the character to output, and the glyph code divided by 524288
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specifies the face number (@pxref{Face Functions}) to use while
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outputting it. (524288 is
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@ifnottex
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2**19.)
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@end ifnottex
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@tex
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$2^{19}$.)
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@end tex
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@xref{Faces}.
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On character terminals, you can set up a @dfn{glyph table} to define
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the meaning of glyph codes. The glyph codes is the value of the
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variable @code{glyph-table}.
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@defvar glyph-table
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The value of this variable is the current glyph table. It should be a
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vector; the @var{g}th element defines glyph code @var{g}.
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If a glyph code is greater than or equal to the length of the glyph
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table, that code is automatically simple. If the value of
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@code{glyph-table} is @code{nil} instead of a vector, then all glyphs
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are simple. The glyph table is not used on graphical displays, only
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on character terminals. On graphical displays, all glyphs are simple.
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@end defvar
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Here are the possible types of elements in the glyph table:
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@table @asis
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@item @var{string}
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Send the characters in @var{string} to the terminal to output
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this glyph. This alternative is available on character terminals,
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but not under a window system.
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@item @var{integer}
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Define this glyph code as an alias for glyph code @var{integer}. You
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can use an alias to specify a face code for the glyph and use a small
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number as its code.
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@item @code{nil}
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This glyph is simple.
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@end table
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@defun create-glyph string
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@tindex create-glyph
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This function returns a newly-allocated glyph code which is set up to
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display by sending @var{string} to the terminal.
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@end defun
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@node Beeping
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@section Beeping
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@cindex beeping
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@cindex bell
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This section describes how to make Emacs ring the bell (or blink the
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screen) to attract the user's attention. Be conservative about how
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often you do this; frequent bells can become irritating. Also be
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careful not to use just beeping when signaling an error is more
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appropriate. (@xref{Errors}.)
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@defun ding &optional do-not-terminate
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@cindex keyboard macro termination
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This function beeps, or flashes the screen (see @code{visible-bell} below).
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It also terminates any keyboard macro currently executing unless
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@var{do-not-terminate} is non-@code{nil}.
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@end defun
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@defun beep &optional do-not-terminate
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This is a synonym for @code{ding}.
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@end defun
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@defopt visible-bell
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This variable determines whether Emacs should flash the screen to
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represent a bell. Non-@code{nil} means yes, @code{nil} means no. This
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is effective on a window system, and on a character-only terminal
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provided the terminal's Termcap entry defines the visible bell
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capability (@samp{vb}).
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@end defopt
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@defvar ring-bell-function
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If this is non-@code{nil}, it specifies how Emacs should ``ring the
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bell.'' Its value should be a function of no arguments. If this is
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non-@code{nil}, it takes precedence over the @code{visible-bell}
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variable.
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@end defvar
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@node Window Systems
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@section Window Systems
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Emacs works with several window systems, most notably the X Window
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System. Both Emacs and X use the term ``window'', but use it
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differently. An Emacs frame is a single window as far as X is
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concerned; the individual Emacs windows are not known to X at all.
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@defvar window-system
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This variable tells Lisp programs what window system Emacs is running
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under. The possible values are
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@table @code
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@item x
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@cindex X Window System
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Emacs is displaying using X.
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@item pc
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Emacs is displaying using MS-DOS.
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@item w32
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Emacs is displaying using Windows.
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@item mac
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Emacs is displaying using a Macintosh.
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@item nil
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Emacs is using a character-based terminal.
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@end table
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@end defvar
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@defvar window-setup-hook
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This variable is a normal hook which Emacs runs after handling the
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initialization files. Emacs runs this hook after it has completed
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loading your init file, the default initialization file (if
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any), and the terminal-specific Lisp code, and running the hook
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@code{term-setup-hook}.
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This hook is used for internal purposes: setting up communication with
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the window system, and creating the initial window. Users should not
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interfere with it.
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@end defvar
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@ignore
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arch-tag: ffdf5714-7ecf-415b-9023-fbc6b409c2c6
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@end ignore
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