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af1996b50b
(User-Level Deletion): Mention optional BACKWARD-ONLY argument to delete-horizontal-space. (Kill Functions, Yanking, Low-Level Kill Ring): clarify and correct description of yank-handler text property at various places.
4051 lines
161 KiB
Plaintext
4051 lines
161 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 Free Software Foundation, Inc.
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@c See the file elisp.texi for copying conditions.
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@setfilename ../info/text
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@node Text, Non-ASCII Characters, Markers, Top
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@chapter Text
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@cindex text
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This chapter describes the functions that deal with the text in a
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buffer. Most examine, insert, or delete text in the current buffer,
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often operating at point or on text adjacent to point. Many are
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interactive. All the functions that change the text provide for undoing
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the changes (@pxref{Undo}).
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Many text-related functions operate on a region of text defined by two
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buffer positions passed in arguments named @var{start} and @var{end}.
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These arguments should be either markers (@pxref{Markers}) or numeric
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character positions (@pxref{Positions}). The order of these arguments
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does not matter; it is all right for @var{start} to be the end of the
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region and @var{end} the beginning. For example, @code{(delete-region 1
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10)} and @code{(delete-region 10 1)} are equivalent. An
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@code{args-out-of-range} error is signaled if either @var{start} or
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@var{end} is outside the accessible portion of the buffer. In an
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interactive call, point and the mark are used for these arguments.
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@cindex buffer contents
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Throughout this chapter, ``text'' refers to the characters in the
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buffer, together with their properties (when relevant). Keep in mind
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that point is always between two characters, and the cursor appears on
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the character after point.
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@menu
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* Near Point:: Examining text in the vicinity of point.
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* Buffer Contents:: Examining text in a general fashion.
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* Comparing Text:: Comparing substrings of buffers.
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* Insertion:: Adding new text to a buffer.
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* Commands for Insertion:: User-level commands to insert text.
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* Deletion:: Removing text from a buffer.
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* User-Level Deletion:: User-level commands to delete text.
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* The Kill Ring:: Where removed text sometimes is saved for later use.
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* Undo:: Undoing changes to the text of a buffer.
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* Maintaining Undo:: How to enable and disable undo information.
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How to control how much information is kept.
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* Filling:: Functions for explicit filling.
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* Margins:: How to specify margins for filling commands.
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* Adaptive Fill:: Adaptive Fill mode chooses a fill prefix from context.
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* Auto Filling:: How auto-fill mode is implemented to break lines.
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* Sorting:: Functions for sorting parts of the buffer.
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* Columns:: Computing horizontal positions, and using them.
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* Indentation:: Functions to insert or adjust indentation.
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* Case Changes:: Case conversion of parts of the buffer.
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* Text Properties:: Assigning Lisp property lists to text characters.
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* Substitution:: Replacing a given character wherever it appears.
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* Transposition:: Swapping two portions of a buffer.
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* Registers:: How registers are implemented. Accessing the text or
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position stored in a register.
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* Base 64:: Conversion to or from base 64 encoding.
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* MD5 Checksum:: Compute the MD5 ``message digest''/``checksum''.
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* Atomic Changes:: Installing several buffer changes ``atomically''.
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* Change Hooks:: Supplying functions to be run when text is changed.
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@end menu
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@node Near Point
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@section Examining Text Near Point
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Many functions are provided to look at the characters around point.
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Several simple functions are described here. See also @code{looking-at}
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in @ref{Regexp Search}.
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In the following four functions, ``beginning'' or ``end'' of buffer
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refers to the beginning or end of the accessible portion.
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@defun char-after &optional position
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This function returns the character in the current buffer at (i.e.,
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immediately after) position @var{position}. If @var{position} is out of
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range for this purpose, either before the beginning of the buffer, or at
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or beyond the end, then the value is @code{nil}. The default for
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@var{position} is point.
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In the following example, assume that the first character in the
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buffer is @samp{@@}:
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@example
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@group
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(char-to-string (char-after 1))
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@result{} "@@"
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@end group
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@end example
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@end defun
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@defun char-before &optional position
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This function returns the character in the current buffer immediately
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before position @var{position}. If @var{position} is out of range for
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this purpose, either at or before the beginning of the buffer, or beyond
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the end, then the value is @code{nil}. The default for
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@var{position} is point.
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@end defun
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@defun following-char
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This function returns the character following point in the current
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buffer. This is similar to @code{(char-after (point))}. However, if
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point is at the end of the buffer, then @code{following-char} returns 0.
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Remember that point is always between characters, and the terminal
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cursor normally appears over the character following point. Therefore,
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the character returned by @code{following-char} is the character the
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cursor is over.
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In this example, point is between the @samp{a} and the @samp{c}.
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@example
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@group
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---------- Buffer: foo ----------
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Gentlemen may cry ``Pea@point{}ce! Peace!,''
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but there is no peace.
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---------- Buffer: foo ----------
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@end group
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@group
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(char-to-string (preceding-char))
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@result{} "a"
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(char-to-string (following-char))
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@result{} "c"
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@end group
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@end example
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@end defun
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@defun preceding-char
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This function returns the character preceding point in the current
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buffer. See above, under @code{following-char}, for an example. If
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point is at the beginning of the buffer, @code{preceding-char} returns
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0.
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@end defun
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@defun bobp
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This function returns @code{t} if point is at the beginning of the
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buffer. If narrowing is in effect, this means the beginning of the
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accessible portion of the text. See also @code{point-min} in
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@ref{Point}.
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@end defun
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@defun eobp
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This function returns @code{t} if point is at the end of the buffer.
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If narrowing is in effect, this means the end of accessible portion of
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the text. See also @code{point-max} in @xref{Point}.
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@end defun
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@defun bolp
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This function returns @code{t} if point is at the beginning of a line.
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@xref{Text Lines}. The beginning of the buffer (or of its accessible
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portion) always counts as the beginning of a line.
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@end defun
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@defun eolp
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This function returns @code{t} if point is at the end of a line. The
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end of the buffer (or of its accessible portion) is always considered
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the end of a line.
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@end defun
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@node Buffer Contents
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@section Examining Buffer Contents
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This section describes functions that allow a Lisp program to
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convert any portion of the text in the buffer into a string.
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@defun buffer-substring start end
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This function returns a string containing a copy of the text of the
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region defined by positions @var{start} and @var{end} in the current
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buffer. If the arguments are not positions in the accessible portion of
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the buffer, @code{buffer-substring} signals an @code{args-out-of-range}
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error.
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It is not necessary for @var{start} to be less than @var{end}; the
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arguments can be given in either order. But most often the smaller
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argument is written first.
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If the text being copied has any text properties, these are copied into
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the string along with the characters they belong to. @xref{Text
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Properties}. However, overlays (@pxref{Overlays}) in the buffer and
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their properties are ignored, not copied.
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@example
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@group
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---------- Buffer: foo ----------
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This is the contents of buffer foo
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---------- Buffer: foo ----------
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@end group
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@group
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(buffer-substring 1 10)
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@result{} "This is t"
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@end group
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@group
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(buffer-substring (point-max) 10)
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@result{} "he contents of buffer foo
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"
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@end group
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@end example
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@end defun
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@defun buffer-substring-no-properties start end
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This is like @code{buffer-substring}, except that it does not copy text
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properties, just the characters themselves. @xref{Text Properties}.
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@end defun
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@defun buffer-string
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This function returns the contents of the entire accessible portion of
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the current buffer as a string. It is equivalent to
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@example
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(buffer-substring (point-min) (point-max))
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@end example
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@example
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@group
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---------- Buffer: foo ----------
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This is the contents of buffer foo
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---------- Buffer: foo ----------
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(buffer-string)
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@result{} "This is the contents of buffer foo
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"
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@end group
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@end example
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@end defun
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@tindex current-word
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@defun current-word &optional strict really-word
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This function returns the symbol (or word) at or near point, as a string.
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The return value includes no text properties.
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If the optional argument @var{really-word} is non-@code{nil}, it finds a
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word; otherwise, it finds a symbol (which includes both word
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characters and symbol constituent characters).
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If the optional argument @var{strict} is non-@code{nil}, then point
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must be in or next to the symbol or word---if no symbol or word is
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there, the function returns @code{nil}. Otherwise, a nearby symbol or
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word on the same line is acceptable.
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@end defun
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@defun thing-at-point thing
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Return the @var{thing} around or next to point, as a string.
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The argument @var{thing} is a symbol which specifies a kind of syntactic
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entity. Possibilities include @code{symbol}, @code{list}, @code{sexp},
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@code{defun}, @code{filename}, @code{url}, @code{word}, @code{sentence},
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@code{whitespace}, @code{line}, @code{page}, and others.
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@example
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---------- Buffer: foo ----------
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Gentlemen may cry ``Pea@point{}ce! Peace!,''
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but there is no peace.
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---------- Buffer: foo ----------
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(thing-at-point 'word)
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@result{} "Peace"
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(thing-at-point 'line)
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@result{} "Gentlemen may cry ``Peace! Peace!,''\n"
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(thing-at-point 'whitespace)
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@result{} nil
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@end example
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@end defun
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@node Comparing Text
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@section Comparing Text
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@cindex comparing buffer text
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This function lets you compare portions of the text in a buffer, without
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copying them into strings first.
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@defun compare-buffer-substrings buffer1 start1 end1 buffer2 start2 end2
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This function lets you compare two substrings of the same buffer or two
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different buffers. The first three arguments specify one substring,
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giving a buffer (or a buffer name) and two positions within the
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buffer. The last three arguments specify the other substring in the
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same way. You can use @code{nil} for @var{buffer1}, @var{buffer2}, or
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both to stand for the current buffer.
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The value is negative if the first substring is less, positive if the
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first is greater, and zero if they are equal. The absolute value of
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the result is one plus the index of the first differing characters
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within the substrings.
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This function ignores case when comparing characters
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if @code{case-fold-search} is non-@code{nil}. It always ignores
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text properties.
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Suppose the current buffer contains the text @samp{foobarbar
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haha!rara!}; then in this example the two substrings are @samp{rbar }
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and @samp{rara!}. The value is 2 because the first substring is greater
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at the second character.
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@example
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(compare-buffer-substrings nil 6 11 nil 16 21)
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@result{} 2
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@end example
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@end defun
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@node Insertion
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@section Inserting Text
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@cindex insertion of text
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@cindex text insertion
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@cindex insertion before point
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@cindex before point, insertion
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@dfn{Insertion} means adding new text to a buffer. The inserted text
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goes at point---between the character before point and the character
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after point. Some insertion functions leave point before the inserted
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text, while other functions leave it after. We call the former
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insertion @dfn{after point} and the latter insertion @dfn{before point}.
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Insertion relocates markers that point at positions after the
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insertion point, so that they stay with the surrounding text
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(@pxref{Markers}). When a marker points at the place of insertion,
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insertion may or may not relocate the marker, depending on the marker's
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insertion type (@pxref{Marker Insertion Types}). Certain special
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functions such as @code{insert-before-markers} relocate all such markers
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to point after the inserted text, regardless of the markers' insertion
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type.
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Insertion functions signal an error if the current buffer is
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read-only or if they insert within read-only text.
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These functions copy text characters from strings and buffers along
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with their properties. The inserted characters have exactly the same
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properties as the characters they were copied from. By contrast,
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characters specified as separate arguments, not part of a string or
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buffer, inherit their text properties from the neighboring text.
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The insertion functions convert text from unibyte to multibyte in
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order to insert in a multibyte buffer, and vice versa---if the text
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comes from a string or from a buffer. However, they do not convert
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unibyte character codes 128 through 255 to multibyte characters, not
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even if the current buffer is a multibyte buffer. @xref{Converting
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Representations}.
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@defun insert &rest args
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This function inserts the strings and/or characters @var{args} into the
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current buffer, at point, moving point forward. In other words, it
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inserts the text before point. An error is signaled unless all
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@var{args} are either strings or characters. The value is @code{nil}.
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@end defun
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@defun insert-before-markers &rest args
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This function inserts the strings and/or characters @var{args} into the
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current buffer, at point, moving point forward. An error is signaled
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unless all @var{args} are either strings or characters. The value is
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@code{nil}.
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This function is unlike the other insertion functions in that it
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relocates markers initially pointing at the insertion point, to point
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after the inserted text. If an overlay begins at the insertion point,
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the inserted text falls outside the overlay; if a nonempty overlay
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ends at the insertion point, the inserted text falls inside that
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overlay.
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@end defun
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@defun insert-char character count &optional inherit
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This function inserts @var{count} instances of @var{character} into the
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current buffer before point. The argument @var{count} should be a
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number, and @var{character} must be a character. The value is @code{nil}.
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This function does not convert unibyte character codes 128 through 255
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to multibyte characters, not even if the current buffer is a multibyte
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buffer. @xref{Converting Representations}.
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If @var{inherit} is non-@code{nil}, then the inserted characters inherit
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sticky text properties from the two characters before and after the
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insertion point. @xref{Sticky Properties}.
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@end defun
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@defun insert-buffer-substring from-buffer-or-name &optional start end
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This function inserts a portion of buffer @var{from-buffer-or-name}
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(which must already exist) into the current buffer before point. The
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text inserted is the region between @var{start} and @var{end}. (These
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arguments default to the beginning and end of the accessible portion of
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that buffer.) This function returns @code{nil}.
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In this example, the form is executed with buffer @samp{bar} as the
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current buffer. We assume that buffer @samp{bar} is initially empty.
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@example
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@group
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---------- Buffer: foo ----------
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We hold these truths to be self-evident, that all
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---------- Buffer: foo ----------
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@end group
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@group
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(insert-buffer-substring "foo" 1 20)
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@result{} nil
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---------- Buffer: bar ----------
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We hold these truth@point{}
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---------- Buffer: bar ----------
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@end group
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@end example
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@end defun
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@defun insert-buffer-substring-no-properties from-buffer-or-name &optional start end
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This is like @code{insert-buffer-substring} except that it does not
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copy any text properties.
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@end defun
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@xref{Sticky Properties}, for other insertion functions that inherit
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text properties from the nearby text in addition to inserting it.
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Whitespace inserted by indentation functions also inherits text
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properties.
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@node Commands for Insertion
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@section User-Level Insertion Commands
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This section describes higher-level commands for inserting text,
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commands intended primarily for the user but useful also in Lisp
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programs.
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@deffn Command insert-buffer from-buffer-or-name
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This command inserts the entire accessible contents of
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@var{from-buffer-or-name} (which must exist) into the current buffer
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after point. It leaves the mark after the inserted text. The value
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is @code{nil}.
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@end deffn
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@deffn Command self-insert-command count
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@cindex character insertion
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@cindex self-insertion
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This command inserts the last character typed; it does so @var{count}
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times, before point, and returns @code{nil}. Most printing characters
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are bound to this command. In routine use, @code{self-insert-command}
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is the most frequently called function in Emacs, but programs rarely use
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it except to install it on a keymap.
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In an interactive call, @var{count} is the numeric prefix argument.
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This command calls @code{auto-fill-function} whenever that is
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non-@code{nil} and the character inserted is in the table
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@code{auto-fill-chars} (@pxref{Auto Filling}).
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@c Cross refs reworded to prevent overfull hbox. --rjc 15mar92
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This command performs abbrev expansion if Abbrev mode is enabled and
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the inserted character does not have word-constituent
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syntax. (@xref{Abbrevs}, and @ref{Syntax Class Table}.)
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This is also responsible for calling @code{blink-paren-function} when
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the inserted character has close parenthesis syntax (@pxref{Blinking}).
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Do not try substituting your own definition of
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@code{self-insert-command} for the standard one. The editor command
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loop handles this function specially.
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@end deffn
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@deffn Command newline &optional number-of-newlines
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This command inserts newlines into the current buffer before point.
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If @var{number-of-newlines} is supplied, that many newline characters
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are inserted.
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@cindex newline and Auto Fill mode
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This function calls @code{auto-fill-function} if the current column
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number is greater than the value of @code{fill-column} and
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@var{number-of-newlines} is @code{nil}. Typically what
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@code{auto-fill-function} does is insert a newline; thus, the overall
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result in this case is to insert two newlines at different places: one
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at point, and another earlier in the line. @code{newline} does not
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auto-fill if @var{number-of-newlines} is non-@code{nil}.
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This command indents to the left margin if that is not zero.
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@xref{Margins}.
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The value returned is @code{nil}. In an interactive call, @var{count}
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is the numeric prefix argument.
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@end deffn
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@deffn Command split-line
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This command splits the current line, moving the portion of the line
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after point down vertically so that it is on the next line directly
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below where it was before. Whitespace is inserted as needed at the
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beginning of the lower line, using the @code{indent-to} function.
|
|
@code{split-line} returns the position of point.
|
|
|
|
Programs hardly ever use this function.
|
|
@end deffn
|
|
|
|
@defvar overwrite-mode
|
|
This variable controls whether overwrite mode is in effect. The value
|
|
should be @code{overwrite-mode-textual}, @code{overwrite-mode-binary},
|
|
or @code{nil}. @code{overwrite-mode-textual} specifies textual
|
|
overwrite mode (treats newlines and tabs specially), and
|
|
@code{overwrite-mode-binary} specifies binary overwrite mode (treats
|
|
newlines and tabs like any other characters).
|
|
@end defvar
|
|
|
|
@node Deletion
|
|
@section Deleting Text
|
|
|
|
@cindex deletion vs killing
|
|
Deletion means removing part of the text in a buffer, without saving
|
|
it in the kill ring (@pxref{The Kill Ring}). Deleted text can't be
|
|
yanked, but can be reinserted using the undo mechanism (@pxref{Undo}).
|
|
Some deletion functions do save text in the kill ring in some special
|
|
cases.
|
|
|
|
All of the deletion functions operate on the current buffer.
|
|
|
|
@deffn Command erase-buffer
|
|
This function deletes the entire text of the current buffer
|
|
(@emph{not} just the accessible portion), leaving it
|
|
empty. If the buffer is read-only, it signals a @code{buffer-read-only}
|
|
error; if some of the text in it is read-only, it signals a
|
|
@code{text-read-only} error. Otherwise, it deletes the text without
|
|
asking for any confirmation. It returns @code{nil}.
|
|
|
|
Normally, deleting a large amount of text from a buffer inhibits further
|
|
auto-saving of that buffer ``because it has shrunk''. However,
|
|
@code{erase-buffer} does not do this, the idea being that the future
|
|
text is not really related to the former text, and its size should not
|
|
be compared with that of the former text.
|
|
@end deffn
|
|
|
|
@deffn Command delete-region start end
|
|
This command deletes the text between positions @var{start} and
|
|
@var{end} in the current buffer, and returns @code{nil}. If point was
|
|
inside the deleted region, its value afterward is @var{start}.
|
|
Otherwise, point relocates with the surrounding text, as markers do.
|
|
@end deffn
|
|
|
|
@defun delete-and-extract-region start end
|
|
@tindex delete-and-extract-region
|
|
This function deletes the text between positions @var{start} and
|
|
@var{end} in the current buffer, and returns a string containing the
|
|
text just deleted.
|
|
|
|
If point was inside the deleted region, its value afterward is
|
|
@var{start}. Otherwise, point relocates with the surrounding text, as
|
|
markers do.
|
|
@end defun
|
|
|
|
@deffn Command delete-char count &optional killp
|
|
This command deletes @var{count} characters directly after point, or
|
|
before point if @var{count} is negative. If @var{killp} is
|
|
non-@code{nil}, then it saves the deleted characters in the kill ring.
|
|
|
|
In an interactive call, @var{count} is the numeric prefix argument, and
|
|
@var{killp} is the unprocessed prefix argument. Therefore, if a prefix
|
|
argument is supplied, the text is saved in the kill ring. If no prefix
|
|
argument is supplied, then one character is deleted, but not saved in
|
|
the kill ring.
|
|
|
|
The value returned is always @code{nil}.
|
|
@end deffn
|
|
|
|
@deffn Command delete-backward-char count &optional killp
|
|
@cindex delete previous char
|
|
This command deletes @var{count} characters directly before point, or
|
|
after point if @var{count} is negative. If @var{killp} is
|
|
non-@code{nil}, then it saves the deleted characters in the kill ring.
|
|
|
|
In an interactive call, @var{count} is the numeric prefix argument, and
|
|
@var{killp} is the unprocessed prefix argument. Therefore, if a prefix
|
|
argument is supplied, the text is saved in the kill ring. If no prefix
|
|
argument is supplied, then one character is deleted, but not saved in
|
|
the kill ring.
|
|
|
|
The value returned is always @code{nil}.
|
|
@end deffn
|
|
|
|
@deffn Command backward-delete-char-untabify count &optional killp
|
|
@cindex tab deletion
|
|
This command deletes @var{count} characters backward, changing tabs
|
|
into spaces. When the next character to be deleted is a tab, it is
|
|
first replaced with the proper number of spaces to preserve alignment
|
|
and then one of those spaces is deleted instead of the tab. If
|
|
@var{killp} is non-@code{nil}, then the command saves the deleted
|
|
characters in the kill ring.
|
|
|
|
Conversion of tabs to spaces happens only if @var{count} is positive.
|
|
If it is negative, exactly @minus{}@var{count} characters after point
|
|
are deleted.
|
|
|
|
In an interactive call, @var{count} is the numeric prefix argument, and
|
|
@var{killp} is the unprocessed prefix argument. Therefore, if a prefix
|
|
argument is supplied, the text is saved in the kill ring. If no prefix
|
|
argument is supplied, then one character is deleted, but not saved in
|
|
the kill ring.
|
|
|
|
The value returned is always @code{nil}.
|
|
@end deffn
|
|
|
|
@defopt backward-delete-char-untabify-method
|
|
This option specifies how @code{backward-delete-char-untabify} should
|
|
deal with whitespace. Possible values include @code{untabify}, the
|
|
default, meaning convert a tab to many spaces and delete one;
|
|
@code{hungry}, meaning delete all tabs and spaces before point with
|
|
one command; @code{all} meaning delete all tabs, spaces and newlines
|
|
before point, and @code{nil}, meaning do nothing special for
|
|
whitespace characters.
|
|
@end defopt
|
|
|
|
@node User-Level Deletion
|
|
@section User-Level Deletion Commands
|
|
|
|
This section describes higher-level commands for deleting text,
|
|
commands intended primarily for the user but useful also in Lisp
|
|
programs.
|
|
|
|
@deffn Command delete-horizontal-space &optional backward-only
|
|
@cindex deleting whitespace
|
|
This function deletes all spaces and tabs around point. It returns
|
|
@code{nil}.
|
|
|
|
If @var{backward-only} is non-@code{nil}, the function deletes
|
|
spaces and tabs before point, but not after point.
|
|
|
|
In the following examples, we call @code{delete-horizontal-space} four
|
|
times, once on each line, with point between the second and third
|
|
characters on the line each time.
|
|
|
|
@example
|
|
@group
|
|
---------- Buffer: foo ----------
|
|
I @point{}thought
|
|
I @point{} thought
|
|
We@point{} thought
|
|
Yo@point{}u thought
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
|
|
@group
|
|
(delete-horizontal-space) ; @r{Four times.}
|
|
@result{} nil
|
|
|
|
---------- Buffer: foo ----------
|
|
Ithought
|
|
Ithought
|
|
Wethought
|
|
You thought
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
@end example
|
|
@end deffn
|
|
|
|
@deffn Command delete-indentation &optional join-following-p
|
|
This function joins the line point is on to the previous line, deleting
|
|
any whitespace at the join and in some cases replacing it with one
|
|
space. If @var{join-following-p} is non-@code{nil},
|
|
@code{delete-indentation} joins this line to the following line
|
|
instead. The function returns @code{nil}.
|
|
|
|
If there is a fill prefix, and the second of the lines being joined
|
|
starts with the prefix, then @code{delete-indentation} deletes the
|
|
fill prefix before joining the lines. @xref{Margins}.
|
|
|
|
In the example below, point is located on the line starting
|
|
@samp{events}, and it makes no difference if there are trailing spaces
|
|
in the preceding line.
|
|
|
|
@smallexample
|
|
@group
|
|
---------- Buffer: foo ----------
|
|
When in the course of human
|
|
@point{} events, it becomes necessary
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
|
|
(delete-indentation)
|
|
@result{} nil
|
|
|
|
@group
|
|
---------- Buffer: foo ----------
|
|
When in the course of human@point{} events, it becomes necessary
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
@end smallexample
|
|
|
|
After the lines are joined, the function @code{fixup-whitespace} is
|
|
responsible for deciding whether to leave a space at the junction.
|
|
@end deffn
|
|
|
|
@deffn Command fixup-whitespace
|
|
This function replaces all the horizontal whitespace surrounding point
|
|
with either one space or no space, according to the context. It
|
|
returns @code{nil}.
|
|
|
|
At the beginning or end of a line, the appropriate amount of space is
|
|
none. Before a character with close parenthesis syntax, or after a
|
|
character with open parenthesis or expression-prefix syntax, no space is
|
|
also appropriate. Otherwise, one space is appropriate. @xref{Syntax
|
|
Class Table}.
|
|
|
|
In the example below, @code{fixup-whitespace} is called the first time
|
|
with point before the word @samp{spaces} in the first line. For the
|
|
second invocation, point is directly after the @samp{(}.
|
|
|
|
@smallexample
|
|
@group
|
|
---------- Buffer: foo ----------
|
|
This has too many @point{}spaces
|
|
This has too many spaces at the start of (@point{} this list)
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
|
|
@group
|
|
(fixup-whitespace)
|
|
@result{} nil
|
|
(fixup-whitespace)
|
|
@result{} nil
|
|
@end group
|
|
|
|
@group
|
|
---------- Buffer: foo ----------
|
|
This has too many spaces
|
|
This has too many spaces at the start of (this list)
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
@end smallexample
|
|
@end deffn
|
|
|
|
@deffn Command just-one-space
|
|
@comment !!SourceFile simple.el
|
|
This command replaces any spaces and tabs around point with a single
|
|
space. It returns @code{nil}.
|
|
@end deffn
|
|
|
|
@deffn Command delete-blank-lines
|
|
This function deletes blank lines surrounding point. If point is on a
|
|
blank line with one or more blank lines before or after it, then all but
|
|
one of them are deleted. If point is on an isolated blank line, then it
|
|
is deleted. If point is on a nonblank line, the command deletes all
|
|
blank lines immediately following it.
|
|
|
|
A blank line is defined as a line containing only tabs and spaces.
|
|
|
|
@code{delete-blank-lines} returns @code{nil}.
|
|
@end deffn
|
|
|
|
@node The Kill Ring
|
|
@section The Kill Ring
|
|
@cindex kill ring
|
|
|
|
@dfn{Kill functions} delete text like the deletion functions, but save
|
|
it so that the user can reinsert it by @dfn{yanking}. Most of these
|
|
functions have @samp{kill-} in their name. By contrast, the functions
|
|
whose names start with @samp{delete-} normally do not save text for
|
|
yanking (though they can still be undone); these are ``deletion''
|
|
functions.
|
|
|
|
Most of the kill commands are primarily for interactive use, and are
|
|
not described here. What we do describe are the functions provided for
|
|
use in writing such commands. You can use these functions to write
|
|
commands for killing text. When you need to delete text for internal
|
|
purposes within a Lisp function, you should normally use deletion
|
|
functions, so as not to disturb the kill ring contents.
|
|
@xref{Deletion}.
|
|
|
|
Killed text is saved for later yanking in the @dfn{kill ring}. This
|
|
is a list that holds a number of recent kills, not just the last text
|
|
kill. We call this a ``ring'' because yanking treats it as having
|
|
elements in a cyclic order. The list is kept in the variable
|
|
@code{kill-ring}, and can be operated on with the usual functions for
|
|
lists; there are also specialized functions, described in this section,
|
|
that treat it as a ring.
|
|
|
|
Some people think this use of the word ``kill'' is unfortunate, since
|
|
it refers to operations that specifically @emph{do not} destroy the
|
|
entities ``killed''. This is in sharp contrast to ordinary life, in
|
|
which death is permanent and ``killed'' entities do not come back to
|
|
life. Therefore, other metaphors have been proposed. For example, the
|
|
term ``cut ring'' makes sense to people who, in pre-computer days, used
|
|
scissors and paste to cut up and rearrange manuscripts. However, it
|
|
would be difficult to change the terminology now.
|
|
|
|
@menu
|
|
* Kill Ring Concepts:: What text looks like in the kill ring.
|
|
* Kill Functions:: Functions that kill text.
|
|
* Yanking:: How yanking is done.
|
|
* Yank Commands:: Commands that access the kill ring.
|
|
* Low-Level Kill Ring:: Functions and variables for kill ring access.
|
|
* Internals of Kill Ring:: Variables that hold kill ring data.
|
|
@end menu
|
|
|
|
@node Kill Ring Concepts
|
|
@comment node-name, next, previous, up
|
|
@subsection Kill Ring Concepts
|
|
|
|
The kill ring records killed text as strings in a list, most recent
|
|
first. A short kill ring, for example, might look like this:
|
|
|
|
@example
|
|
("some text" "a different piece of text" "even older text")
|
|
@end example
|
|
|
|
@noindent
|
|
When the list reaches @code{kill-ring-max} entries in length, adding a
|
|
new entry automatically deletes the last entry.
|
|
|
|
When kill commands are interwoven with other commands, each kill
|
|
command makes a new entry in the kill ring. Multiple kill commands in
|
|
succession build up a single kill ring entry, which would be yanked as a
|
|
unit; the second and subsequent consecutive kill commands add text to
|
|
the entry made by the first one.
|
|
|
|
For yanking, one entry in the kill ring is designated the ``front'' of
|
|
the ring. Some yank commands ``rotate'' the ring by designating a
|
|
different element as the ``front.'' But this virtual rotation doesn't
|
|
change the list itself---the most recent entry always comes first in the
|
|
list.
|
|
|
|
@node Kill Functions
|
|
@comment node-name, next, previous, up
|
|
@subsection Functions for Killing
|
|
|
|
@code{kill-region} is the usual subroutine for killing text. Any
|
|
command that calls this function is a ``kill command'' (and should
|
|
probably have @samp{kill} in its name). @code{kill-region} puts the
|
|
newly killed text in a new element at the beginning of the kill ring or
|
|
adds it to the most recent element. It determines automatically (using
|
|
@code{last-command}) whether the previous command was a kill command,
|
|
and if so appends the killed text to the most recent entry.
|
|
|
|
@deffn Command kill-region start end &optional yank-handler
|
|
This function kills the text in the region defined by @var{start} and
|
|
@var{end}. The text is deleted but saved in the kill ring, along with
|
|
its text properties. The value is always @code{nil}.
|
|
|
|
In an interactive call, @var{start} and @var{end} are point and
|
|
the mark.
|
|
|
|
@c Emacs 19 feature
|
|
If the buffer or text is read-only, @code{kill-region} modifies the kill
|
|
ring just the same, then signals an error without modifying the buffer.
|
|
This is convenient because it lets the user use a series of kill
|
|
commands to copy text from a read-only buffer into the kill ring.
|
|
|
|
If @var{yank-handler} is non-@code{nil}, this puts that value onto
|
|
the string of killed text, as a @code{yank-handler} text property.
|
|
@xref{Yanking}. Note that if @var{yank-handler} is @code{nil}, any
|
|
@code{yank-handler} properties present on the killed text are copied
|
|
onto the kill ring, like other text properties.
|
|
@end deffn
|
|
|
|
@defopt kill-read-only-ok
|
|
If this option is non-@code{nil}, @code{kill-region} does not signal an
|
|
error if the buffer or text is read-only. Instead, it simply returns,
|
|
updating the kill ring but not changing the buffer.
|
|
@end defopt
|
|
|
|
@deffn Command copy-region-as-kill start end
|
|
This command saves the region defined by @var{start} and @var{end} on
|
|
the kill ring (including text properties), but does not delete the text
|
|
from the buffer. It returns @code{nil}.
|
|
|
|
The command does not set @code{this-command} to @code{kill-region}, so a
|
|
subsequent kill command does not append to the same kill ring entry.
|
|
|
|
Don't call @code{copy-region-as-kill} in Lisp programs unless you aim to
|
|
support Emacs 18. For newer Emacs versions, it is better to use
|
|
@code{kill-new} or @code{kill-append} instead. @xref{Low-Level Kill
|
|
Ring}.
|
|
@end deffn
|
|
|
|
@node Yanking
|
|
@subsection Yanking
|
|
|
|
Yanking means inserting text from the kill ring, but it does
|
|
not insert the text blindly. Yank commands and some other commands
|
|
use @code{insert-for-yank} to perform special processing on the
|
|
text that they copy into the buffer.
|
|
|
|
@defun insert-for-yank string
|
|
This function normally works like @code{insert} except that it doesn't
|
|
insert the text properties in the @code{yank-excluded-properties}
|
|
list. However, if any part of @var{string} has a non-@code{nil}
|
|
@code{yank-handler} text property, that property can do various
|
|
special processing on that part of the text being inserted.
|
|
@end defun
|
|
|
|
@defun insert-buffer-substring-as-yank buf &optional start end
|
|
This function resembles @code{insert-buffer-substring} except that it
|
|
doesn't insert the text properties in the
|
|
@code{yank-excluded-properties} list.
|
|
@end defun
|
|
|
|
You can put a @code{yank-handler} text property on all or part of
|
|
the text to control how it will be inserted if it is yanked. The
|
|
@code{insert-for-yank} function looks for that property. The property
|
|
value must be a list of one to four elements, with the following
|
|
format (where elements after the first may be omitted):
|
|
|
|
@example
|
|
(@var{function} @var{param} @var{noexclude} @var{undo})
|
|
@end example
|
|
|
|
Here is what the elements do:
|
|
|
|
@table @var
|
|
@item function
|
|
When @var{function} is present and non-@code{nil}, it is called instead of
|
|
@code{insert} to insert the string. @var{function} takes one
|
|
argument---the string to insert.
|
|
|
|
@item param
|
|
If @var{param} is present and non-@code{nil}, it replaces @var{string}
|
|
(or the part of @var{string} being processed) as the object passed to
|
|
@var{function} (or @code{insert}); for example, if @var{function} is
|
|
@code{yank-rectangle}, @var{param} should be a list of strings to
|
|
insert as a rectangle.
|
|
|
|
@item noexclude
|
|
If @var{noexclude} is present and non-@code{nil}, the normal removal of the
|
|
yank-excluded-properties is not performed; instead @var{function} is
|
|
responsible for removing those properties. This may be necessary
|
|
if @var{function} adjusts point before or after inserting the object.
|
|
|
|
@item undo
|
|
If @var{undo} is present and non-@code{nil}, it is a function that will be
|
|
called by @code{yank-pop} to undo the insertion of the current object.
|
|
It is called with two arguments, the start and end of the current
|
|
region. @var{function} can set @code{yank-undo-function} to override
|
|
the @var{undo} value.
|
|
@end table
|
|
|
|
@node Yank Commands
|
|
@comment node-name, next, previous, up
|
|
@subsection Functions for Yanking
|
|
|
|
@dfn{Yanking} means reinserting an entry of previously killed text
|
|
from the kill ring. The text properties are copied too.
|
|
|
|
@deffn Command yank &optional arg
|
|
@cindex inserting killed text
|
|
This command inserts before point the text at the front of the
|
|
kill ring. It positions the mark at the beginning of that text, and
|
|
point at the end.
|
|
|
|
If @var{arg} is a non-@code{nil} list (which occurs interactively when
|
|
the user types @kbd{C-u} with no digits), then @code{yank} inserts the
|
|
text as described above, but puts point before the yanked text and
|
|
puts the mark after it.
|
|
|
|
If @var{arg} is a number, then @code{yank} inserts the @var{arg}th
|
|
most recently killed text---the @var{arg}th element of the kill ring
|
|
list, counted cyclically from the front, which is considered the
|
|
first element for this purpose.
|
|
|
|
@code{yank} does not alter the contents of the kill ring, unless it
|
|
used text provided by another program, in which case it pushes that text
|
|
onto the kill ring. However if @var{arg} is an integer different from
|
|
one, it rotates the kill ring to place the yanked string at the front.
|
|
|
|
@code{yank} returns @code{nil}.
|
|
@end deffn
|
|
|
|
@deffn Command yank-pop &optional arg
|
|
This command replaces the just-yanked entry from the kill ring with a
|
|
different entry from the kill ring.
|
|
|
|
This is allowed only immediately after a @code{yank} or another
|
|
@code{yank-pop}. At such a time, the region contains text that was just
|
|
inserted by yanking. @code{yank-pop} deletes that text and inserts in
|
|
its place a different piece of killed text. It does not add the deleted
|
|
text to the kill ring, since it is already in the kill ring somewhere.
|
|
It does however rotate the kill ring to place the newly yanked string at
|
|
the front.
|
|
|
|
If @var{arg} is @code{nil}, then the replacement text is the previous
|
|
element of the kill ring. If @var{arg} is numeric, the replacement is
|
|
the @var{arg}th previous kill. If @var{arg} is negative, a more recent
|
|
kill is the replacement.
|
|
|
|
The sequence of kills in the kill ring wraps around, so that after the
|
|
oldest one comes the newest one, and before the newest one goes the
|
|
oldest.
|
|
|
|
The return value is always @code{nil}.
|
|
@end deffn
|
|
|
|
@defvar yank-undo-function
|
|
If this variable is non-@code{nil}, the function @code{yank-pop} uses
|
|
its value instead of @code{delete-region} to delete the text
|
|
inserted by the previous @code{yank} or
|
|
@code{yank-pop} command. The value must be a function of two
|
|
arguments, the start and end of the current region.
|
|
|
|
The function @code{insert-for-yank} automatically sets this variable
|
|
according to the @var{undo} element of the @code{yank-handler}
|
|
text property, if there is one.
|
|
@end defvar
|
|
|
|
@node Low-Level Kill Ring
|
|
@subsection Low-Level Kill Ring
|
|
|
|
These functions and variables provide access to the kill ring at a
|
|
lower level, but still convenient for use in Lisp programs, because they
|
|
take care of interaction with window system selections
|
|
(@pxref{Window System Selections}).
|
|
|
|
@defun current-kill n &optional do-not-move
|
|
The function @code{current-kill} rotates the yanking pointer, which
|
|
designates the ``front'' of the kill ring, by @var{n} places (from newer
|
|
kills to older ones), and returns the text at that place in the ring.
|
|
|
|
If the optional second argument @var{do-not-move} is non-@code{nil},
|
|
then @code{current-kill} doesn't alter the yanking pointer; it just
|
|
returns the @var{n}th kill, counting from the current yanking pointer.
|
|
|
|
If @var{n} is zero, indicating a request for the latest kill,
|
|
@code{current-kill} calls the value of
|
|
@code{interprogram-paste-function} (documented below) before
|
|
consulting the kill ring. If that value is a function and calling it
|
|
returns a string, @code{current-kill} pushes that string onto the kill
|
|
ring and returns it. It also sets the yanking pointer to point to
|
|
that new entry, regardless of the value of @var{do-not-move}.
|
|
Otherwise, @code{current-kill} does not treat a zero value for @var{n}
|
|
specially: it returns the entry pointed at by the yanking pointer and
|
|
does not move the yanking pointer.
|
|
@end defun
|
|
|
|
@defun kill-new string &optional replace yank-handler
|
|
This function pushes the text @var{string} onto the kill ring and
|
|
makes the yanking pointer point to it. It discards the oldest entry
|
|
if appropriate. It also invokes the value of
|
|
@code{interprogram-cut-function} (see below).
|
|
|
|
If @var{replace} is non-@code{nil}, then @code{kill-new} replaces the
|
|
first element of the kill ring with @var{string}, rather than pushing
|
|
@var{string} onto the kill ring.
|
|
|
|
If @var{yank-handler} is non-@code{nil}, this puts that value onto
|
|
the string of killed text, as a @code{yank-handler} property.
|
|
@xref{Yanking}. Note that if @var{yank-handler} is @code{nil}, then
|
|
@code{kill-new} copies any @code{yank-handler} properties present on
|
|
@var{string} onto the kill ring, as it does with other text properties.
|
|
@end defun
|
|
|
|
@defun kill-append string before-p &optional yank-handler
|
|
This function appends the text @var{string} to the first entry in the
|
|
kill ring and makes the yanking pointer point to the combined entry.
|
|
Normally @var{string} goes at the end of the entry, but if
|
|
@var{before-p} is non-@code{nil}, it goes at the beginning. This
|
|
function also invokes the value of @code{interprogram-cut-function}
|
|
(see below). This handles @var{yank-handler} just like
|
|
@code{kill-new}, except that if @var{yank-handler} is different from
|
|
the @code{yank-handler} property of the first entry of the kill ring,
|
|
@code{kill-append} pushes the concatenated string onto the kill ring,
|
|
instead of replacing the original first entry with it.
|
|
@end defun
|
|
|
|
@defvar interprogram-paste-function
|
|
This variable provides a way of transferring killed text from other
|
|
programs, when you are using a window system. Its value should be
|
|
@code{nil} or a function of no arguments.
|
|
|
|
If the value is a function, @code{current-kill} calls it to get the
|
|
``most recent kill''. If the function returns a non-@code{nil} value,
|
|
then that value is used as the ``most recent kill''. If it returns
|
|
@code{nil}, then the front of the kill ring is used.
|
|
|
|
The normal use of this hook is to get the window system's primary
|
|
selection as the most recent kill, even if the selection belongs to
|
|
another application. @xref{Window System Selections}.
|
|
@end defvar
|
|
|
|
@defvar interprogram-cut-function
|
|
This variable provides a way of communicating killed text to other
|
|
programs, when you are using a window system. Its value should be
|
|
@code{nil} or a function of one required and one optional argument.
|
|
|
|
If the value is a function, @code{kill-new} and @code{kill-append} call
|
|
it with the new first element of the kill ring as the first argument.
|
|
The second, optional, argument has the same meaning as the @var{push}
|
|
argument to @code{x-set-cut-buffer} (@pxref{Definition of
|
|
x-set-cut-buffer}) and only affects the second and later cut buffers.
|
|
|
|
The normal use of this hook is to set the window system's primary
|
|
selection (and first cut buffer) from the newly killed text.
|
|
@xref{Window System Selections}.
|
|
@end defvar
|
|
|
|
@node Internals of Kill Ring
|
|
@comment node-name, next, previous, up
|
|
@subsection Internals of the Kill Ring
|
|
|
|
The variable @code{kill-ring} holds the kill ring contents, in the
|
|
form of a list of strings. The most recent kill is always at the front
|
|
of the list.
|
|
|
|
The @code{kill-ring-yank-pointer} variable points to a link in the
|
|
kill ring list, whose @sc{car} is the text to yank next. We say it
|
|
identifies the ``front'' of the ring. Moving
|
|
@code{kill-ring-yank-pointer} to a different link is called
|
|
@dfn{rotating the kill ring}. We call the kill ring a ``ring'' because
|
|
the functions that move the yank pointer wrap around from the end of the
|
|
list to the beginning, or vice-versa. Rotation of the kill ring is
|
|
virtual; it does not change the value of @code{kill-ring}.
|
|
|
|
Both @code{kill-ring} and @code{kill-ring-yank-pointer} are Lisp
|
|
variables whose values are normally lists. The word ``pointer'' in the
|
|
name of the @code{kill-ring-yank-pointer} indicates that the variable's
|
|
purpose is to identify one element of the list for use by the next yank
|
|
command.
|
|
|
|
The value of @code{kill-ring-yank-pointer} is always @code{eq} to one
|
|
of the links in the kill ring list. The element it identifies is the
|
|
@sc{car} of that link. Kill commands, which change the kill ring, also
|
|
set this variable to the value of @code{kill-ring}. The effect is to
|
|
rotate the ring so that the newly killed text is at the front.
|
|
|
|
Here is a diagram that shows the variable @code{kill-ring-yank-pointer}
|
|
pointing to the second entry in the kill ring @code{("some text" "a
|
|
different piece of text" "yet older text")}.
|
|
|
|
@example
|
|
@group
|
|
kill-ring ---- kill-ring-yank-pointer
|
|
| |
|
|
| v
|
|
| --- --- --- --- --- ---
|
|
--> | | |------> | | |--> | | |--> nil
|
|
--- --- --- --- --- ---
|
|
| | |
|
|
| | |
|
|
| | -->"yet older text"
|
|
| |
|
|
| --> "a different piece of text"
|
|
|
|
|
--> "some text"
|
|
@end group
|
|
@end example
|
|
|
|
@noindent
|
|
This state of affairs might occur after @kbd{C-y} (@code{yank})
|
|
immediately followed by @kbd{M-y} (@code{yank-pop}).
|
|
|
|
@defvar kill-ring
|
|
This variable holds the list of killed text sequences, most recently
|
|
killed first.
|
|
@end defvar
|
|
|
|
@defvar kill-ring-yank-pointer
|
|
This variable's value indicates which element of the kill ring is at the
|
|
``front'' of the ring for yanking. More precisely, the value is a tail
|
|
of the value of @code{kill-ring}, and its @sc{car} is the kill string
|
|
that @kbd{C-y} should yank.
|
|
@end defvar
|
|
|
|
@defopt kill-ring-max
|
|
The value of this variable is the maximum length to which the kill
|
|
ring can grow, before elements are thrown away at the end. The default
|
|
value for @code{kill-ring-max} is 60.
|
|
@end defopt
|
|
|
|
@node Undo
|
|
@comment node-name, next, previous, up
|
|
@section Undo
|
|
@cindex redo
|
|
|
|
Most buffers have an @dfn{undo list}, which records all changes made
|
|
to the buffer's text so that they can be undone. (The buffers that
|
|
don't have one are usually special-purpose buffers for which Emacs
|
|
assumes that undoing is not useful.) All the primitives that modify the
|
|
text in the buffer automatically add elements to the front of the undo
|
|
list, which is in the variable @code{buffer-undo-list}.
|
|
|
|
@defvar buffer-undo-list
|
|
This variable's value is the undo list of the current buffer.
|
|
A value of @code{t} disables the recording of undo information.
|
|
@end defvar
|
|
|
|
Here are the kinds of elements an undo list can have:
|
|
|
|
@table @code
|
|
@item @var{position}
|
|
This kind of element records a previous value of point; undoing this
|
|
element moves point to @var{position}. Ordinary cursor motion does not
|
|
make any sort of undo record, but deletion operations use these entries
|
|
to record where point was before the command.
|
|
|
|
@item (@var{beg} . @var{end})
|
|
This kind of element indicates how to delete text that was inserted.
|
|
Upon insertion, the text occupied the range @var{beg}--@var{end} in the
|
|
buffer.
|
|
|
|
@item (@var{text} . @var{position})
|
|
This kind of element indicates how to reinsert text that was deleted.
|
|
The deleted text itself is the string @var{text}. The place to
|
|
reinsert it is @code{(abs @var{position})}. If @var{position} is
|
|
positive, point was at the beginning of the deleted text, otherwise it
|
|
was at the end.
|
|
|
|
@item (t @var{high} . @var{low})
|
|
This kind of element indicates that an unmodified buffer became
|
|
modified. The elements @var{high} and @var{low} are two integers, each
|
|
recording 16 bits of the visited file's modification time as of when it
|
|
was previously visited or saved. @code{primitive-undo} uses those
|
|
values to determine whether to mark the buffer as unmodified once again;
|
|
it does so only if the file's modification time matches those numbers.
|
|
|
|
@item (nil @var{property} @var{value} @var{beg} . @var{end})
|
|
This kind of element records a change in a text property.
|
|
Here's how you might undo the change:
|
|
|
|
@example
|
|
(put-text-property @var{beg} @var{end} @var{property} @var{value})
|
|
@end example
|
|
|
|
@item (@var{marker} . @var{adjustment})
|
|
This kind of element records the fact that the marker @var{marker} was
|
|
relocated due to deletion of surrounding text, and that it moved
|
|
@var{adjustment} character positions. Undoing this element moves
|
|
@var{marker} @minus{} @var{adjustment} characters.
|
|
|
|
@item nil
|
|
This element is a boundary. The elements between two boundaries are
|
|
called a @dfn{change group}; normally, each change group corresponds to
|
|
one keyboard command, and undo commands normally undo an entire group as
|
|
a unit.
|
|
@end table
|
|
|
|
@defun undo-boundary
|
|
This function places a boundary element in the undo list. The undo
|
|
command stops at such a boundary, and successive undo commands undo
|
|
to earlier and earlier boundaries. This function returns @code{nil}.
|
|
|
|
The editor command loop automatically creates an undo boundary before
|
|
each key sequence is executed. Thus, each undo normally undoes the
|
|
effects of one command. Self-inserting input characters are an
|
|
exception. The command loop makes a boundary for the first such
|
|
character; the next 19 consecutive self-inserting input characters do
|
|
not make boundaries, and then the 20th does, and so on as long as
|
|
self-inserting characters continue.
|
|
|
|
All buffer modifications add a boundary whenever the previous undoable
|
|
change was made in some other buffer. This is to ensure that
|
|
each command makes a boundary in each buffer where it makes changes.
|
|
|
|
Calling this function explicitly is useful for splitting the effects of
|
|
a command into more than one unit. For example, @code{query-replace}
|
|
calls @code{undo-boundary} after each replacement, so that the user can
|
|
undo individual replacements one by one.
|
|
@end defun
|
|
|
|
@defun primitive-undo count list
|
|
This is the basic function for undoing elements of an undo list.
|
|
It undoes the first @var{count} elements of @var{list}, returning
|
|
the rest of @var{list}. You could write this function in Lisp,
|
|
but it is convenient to have it in C.
|
|
|
|
@code{primitive-undo} adds elements to the buffer's undo list when it
|
|
changes the buffer. Undo commands avoid confusion by saving the undo
|
|
list value at the beginning of a sequence of undo operations. Then the
|
|
undo operations use and update the saved value. The new elements added
|
|
by undoing are not part of this saved value, so they don't interfere with
|
|
continuing to undo.
|
|
@end defun
|
|
|
|
@node Maintaining Undo
|
|
@section Maintaining Undo Lists
|
|
|
|
This section describes how to enable and disable undo information for
|
|
a given buffer. It also explains how the undo list is truncated
|
|
automatically so it doesn't get too big.
|
|
|
|
Recording of undo information in a newly created buffer is normally
|
|
enabled to start with; but if the buffer name starts with a space, the
|
|
undo recording is initially disabled. You can explicitly enable or
|
|
disable undo recording with the following two functions, or by setting
|
|
@code{buffer-undo-list} yourself.
|
|
|
|
@deffn Command buffer-enable-undo &optional buffer-or-name
|
|
This command enables recording undo information for buffer
|
|
@var{buffer-or-name}, so that subsequent changes can be undone. If no
|
|
argument is supplied, then the current buffer is used. This function
|
|
does nothing if undo recording is already enabled in the buffer. It
|
|
returns @code{nil}.
|
|
|
|
In an interactive call, @var{buffer-or-name} is the current buffer.
|
|
You cannot specify any other buffer.
|
|
@end deffn
|
|
|
|
@deffn Command buffer-disable-undo &optional buffer-or-name
|
|
@deffnx Command buffer-flush-undo &optional buffer-or-name
|
|
@cindex disable undo
|
|
This function discards the undo list of @var{buffer-or-name}, and disables
|
|
further recording of undo information. As a result, it is no longer
|
|
possible to undo either previous changes or any subsequent changes. If
|
|
the undo list of @var{buffer-or-name} is already disabled, this function
|
|
has no effect.
|
|
|
|
This function returns @code{nil}.
|
|
|
|
The name @code{buffer-flush-undo} is not considered obsolete, but the
|
|
preferred name is @code{buffer-disable-undo}.
|
|
@end deffn
|
|
|
|
As editing continues, undo lists get longer and longer. To prevent
|
|
them from using up all available memory space, garbage collection trims
|
|
them back to size limits you can set. (For this purpose, the ``size''
|
|
of an undo list measures the cons cells that make up the list, plus the
|
|
strings of deleted text.) Two variables control the range of acceptable
|
|
sizes: @code{undo-limit} and @code{undo-strong-limit}.
|
|
|
|
@defvar undo-limit
|
|
This is the soft limit for the acceptable size of an undo list. The
|
|
change group at which this size is exceeded is the last one kept.
|
|
@end defvar
|
|
|
|
@defvar undo-strong-limit
|
|
This is the upper limit for the acceptable size of an undo list. The
|
|
change group at which this size is exceeded is discarded itself (along
|
|
with all older change groups). There is one exception: the very latest
|
|
change group is never discarded no matter how big it is.
|
|
@end defvar
|
|
|
|
@node Filling
|
|
@comment node-name, next, previous, up
|
|
@section Filling
|
|
@cindex filling, explicit
|
|
|
|
@dfn{Filling} means adjusting the lengths of lines (by moving the line
|
|
breaks) so that they are nearly (but no greater than) a specified
|
|
maximum width. Additionally, lines can be @dfn{justified}, which means
|
|
inserting spaces to make the left and/or right margins line up
|
|
precisely. The width is controlled by the variable @code{fill-column}.
|
|
For ease of reading, lines should be no longer than 70 or so columns.
|
|
|
|
You can use Auto Fill mode (@pxref{Auto Filling}) to fill text
|
|
automatically as you insert it, but changes to existing text may leave
|
|
it improperly filled. Then you must fill the text explicitly.
|
|
|
|
Most of the commands in this section return values that are not
|
|
meaningful. All the functions that do filling take note of the current
|
|
left margin, current right margin, and current justification style
|
|
(@pxref{Margins}). If the current justification style is
|
|
@code{none}, the filling functions don't actually do anything.
|
|
|
|
Several of the filling functions have an argument @var{justify}.
|
|
If it is non-@code{nil}, that requests some kind of justification. It
|
|
can be @code{left}, @code{right}, @code{full}, or @code{center}, to
|
|
request a specific style of justification. If it is @code{t}, that
|
|
means to use the current justification style for this part of the text
|
|
(see @code{current-justification}, below). Any other value is treated
|
|
as @code{full}.
|
|
|
|
When you call the filling functions interactively, using a prefix
|
|
argument implies the value @code{full} for @var{justify}.
|
|
|
|
@deffn Command fill-paragraph justify
|
|
@cindex filling a paragraph
|
|
This command fills the paragraph at or after point. If
|
|
@var{justify} is non-@code{nil}, each line is justified as well.
|
|
It uses the ordinary paragraph motion commands to find paragraph
|
|
boundaries. @xref{Paragraphs,,, emacs, The GNU Emacs Manual}.
|
|
@end deffn
|
|
|
|
@deffn Command fill-region start end &optional justify nosqueeze to-eop
|
|
This command fills each of the paragraphs in the region from @var{start}
|
|
to @var{end}. It justifies as well if @var{justify} is
|
|
non-@code{nil}.
|
|
|
|
If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace
|
|
other than line breaks untouched. If @var{to-eop} is non-@code{nil},
|
|
that means to keep filling to the end of the paragraph---or the next hard
|
|
newline, if @code{use-hard-newlines} is enabled (see below).
|
|
|
|
The variable @code{paragraph-separate} controls how to distinguish
|
|
paragraphs. @xref{Standard Regexps}.
|
|
@end deffn
|
|
|
|
@deffn Command fill-individual-paragraphs start end &optional justify citation-regexp
|
|
This command fills each paragraph in the region according to its
|
|
individual fill prefix. Thus, if the lines of a paragraph were indented
|
|
with spaces, the filled paragraph will remain indented in the same
|
|
fashion.
|
|
|
|
The first two arguments, @var{start} and @var{end}, are the beginning
|
|
and end of the region to be filled. The third and fourth arguments,
|
|
@var{justify} and @var{citation-regexp}, are optional. If
|
|
@var{justify} is non-@code{nil}, the paragraphs are justified as
|
|
well as filled. If @var{citation-regexp} is non-@code{nil}, it means the
|
|
function is operating on a mail message and therefore should not fill
|
|
the header lines. If @var{citation-regexp} is a string, it is used as
|
|
a regular expression; if it matches the beginning of a line, that line
|
|
is treated as a citation marker.
|
|
|
|
Ordinarily, @code{fill-individual-paragraphs} regards each change in
|
|
indentation as starting a new paragraph. If
|
|
@code{fill-individual-varying-indent} is non-@code{nil}, then only
|
|
separator lines separate paragraphs. That mode can handle indented
|
|
paragraphs with additional indentation on the first line.
|
|
@end deffn
|
|
|
|
@defopt fill-individual-varying-indent
|
|
This variable alters the action of @code{fill-individual-paragraphs} as
|
|
described above.
|
|
@end defopt
|
|
|
|
@deffn Command fill-region-as-paragraph start end &optional justify nosqueeze squeeze-after
|
|
This command considers a region of text as a single paragraph and fills
|
|
it. If the region was made up of many paragraphs, the blank lines
|
|
between paragraphs are removed. This function justifies as well as
|
|
filling when @var{justify} is non-@code{nil}.
|
|
|
|
In an interactive call, any prefix argument requests justification.
|
|
|
|
If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace
|
|
other than line breaks untouched. If @var{squeeze-after} is
|
|
non-@code{nil}, it specifies a position in the region, and means don't
|
|
canonicalize spaces before that position.
|
|
|
|
In Adaptive Fill mode, this command calls @code{fill-context-prefix} to
|
|
choose a fill prefix by default. @xref{Adaptive Fill}.
|
|
@end deffn
|
|
|
|
@deffn Command justify-current-line &optional how eop nosqueeze
|
|
This command inserts spaces between the words of the current line so
|
|
that the line ends exactly at @code{fill-column}. It returns
|
|
@code{nil}.
|
|
|
|
The argument @var{how}, if non-@code{nil} specifies explicitly the style
|
|
of justification. It can be @code{left}, @code{right}, @code{full},
|
|
@code{center}, or @code{none}. If it is @code{t}, that means to do
|
|
follow specified justification style (see @code{current-justification},
|
|
below). @code{nil} means to do full justification.
|
|
|
|
If @var{eop} is non-@code{nil}, that means do left-justification if
|
|
@code{current-justification} specifies full justification. This is used
|
|
for the last line of a paragraph; even if the paragraph as a whole is
|
|
fully justified, the last line should not be.
|
|
|
|
If @var{nosqueeze} is non-@code{nil}, that means do not change interior
|
|
whitespace.
|
|
@end deffn
|
|
|
|
@defopt default-justification
|
|
This variable's value specifies the style of justification to use for
|
|
text that doesn't specify a style with a text property. The possible
|
|
values are @code{left}, @code{right}, @code{full}, @code{center}, or
|
|
@code{none}. The default value is @code{left}.
|
|
@end defopt
|
|
|
|
@defun current-justification
|
|
This function returns the proper justification style to use for filling
|
|
the text around point.
|
|
@end defun
|
|
|
|
@defopt sentence-end-double-space
|
|
If this variable is non-@code{nil}, a period followed by just one space
|
|
does not count as the end of a sentence, and the filling functions
|
|
avoid breaking the line at such a place.
|
|
@end defopt
|
|
|
|
@defvar fill-paragraph-function
|
|
This variable provides a way for major modes to override the filling of
|
|
paragraphs. If the value is non-@code{nil}, @code{fill-paragraph} calls
|
|
this function to do the work. If the function returns a non-@code{nil}
|
|
value, @code{fill-paragraph} assumes the job is done, and immediately
|
|
returns that value.
|
|
|
|
The usual use of this feature is to fill comments in programming
|
|
language modes. If the function needs to fill a paragraph in the usual
|
|
way, it can do so as follows:
|
|
|
|
@example
|
|
(let ((fill-paragraph-function nil))
|
|
(fill-paragraph arg))
|
|
@end example
|
|
@end defvar
|
|
|
|
@defvar use-hard-newlines
|
|
If this variable is non-@code{nil}, the filling functions do not delete
|
|
newlines that have the @code{hard} text property. These ``hard
|
|
newlines'' act as paragraph separators.
|
|
@end defvar
|
|
|
|
@node Margins
|
|
@section Margins for Filling
|
|
|
|
@defopt fill-prefix
|
|
This buffer-local variable specifies a string of text that appears at
|
|
the beginning
|
|
of normal text lines and should be disregarded when filling them. Any
|
|
line that fails to start with the fill prefix is considered the start of
|
|
a paragraph; so is any line that starts with the fill prefix followed by
|
|
additional whitespace. Lines that start with the fill prefix but no
|
|
additional whitespace are ordinary text lines that can be filled
|
|
together. The resulting filled lines also start with the fill prefix.
|
|
|
|
The fill prefix follows the left margin whitespace, if any.
|
|
@end defopt
|
|
|
|
@defopt fill-column
|
|
This buffer-local variable specifies the maximum width of filled lines.
|
|
Its value should be an integer, which is a number of columns. All the
|
|
filling, justification, and centering commands are affected by this
|
|
variable, including Auto Fill mode (@pxref{Auto Filling}).
|
|
|
|
As a practical matter, if you are writing text for other people to
|
|
read, you should set @code{fill-column} to no more than 70. Otherwise
|
|
the line will be too long for people to read comfortably, and this can
|
|
make the text seem clumsy.
|
|
@end defopt
|
|
|
|
@defvar default-fill-column
|
|
The value of this variable is the default value for @code{fill-column} in
|
|
buffers that do not override it. This is the same as
|
|
@code{(default-value 'fill-column)}.
|
|
|
|
The default value for @code{default-fill-column} is 70.
|
|
@end defvar
|
|
|
|
@deffn Command set-left-margin from to margin
|
|
This sets the @code{left-margin} property on the text from @var{from} to
|
|
@var{to} to the value @var{margin}. If Auto Fill mode is enabled, this
|
|
command also refills the region to fit the new margin.
|
|
@end deffn
|
|
|
|
@deffn Command set-right-margin from to margin
|
|
This sets the @code{right-margin} property on the text from @var{from}
|
|
to @var{to} to the value @var{margin}. If Auto Fill mode is enabled,
|
|
this command also refills the region to fit the new margin.
|
|
@end deffn
|
|
|
|
@defun current-left-margin
|
|
This function returns the proper left margin value to use for filling
|
|
the text around point. The value is the sum of the @code{left-margin}
|
|
property of the character at the start of the current line (or zero if
|
|
none), and the value of the variable @code{left-margin}.
|
|
@end defun
|
|
|
|
@defun current-fill-column
|
|
This function returns the proper fill column value to use for filling
|
|
the text around point. The value is the value of the @code{fill-column}
|
|
variable, minus the value of the @code{right-margin} property of the
|
|
character after point.
|
|
@end defun
|
|
|
|
@deffn Command move-to-left-margin &optional n force
|
|
This function moves point to the left margin of the current line. The
|
|
column moved to is determined by calling the function
|
|
@code{current-left-margin}. If the argument @var{n} is non-@code{nil},
|
|
@code{move-to-left-margin} moves forward @var{n}@minus{}1 lines first.
|
|
|
|
If @var{force} is non-@code{nil}, that says to fix the line's
|
|
indentation if that doesn't match the left margin value.
|
|
@end deffn
|
|
|
|
@defun delete-to-left-margin &optional from to
|
|
This function removes left margin indentation from the text between
|
|
@var{from} and @var{to}. The amount of indentation to delete is
|
|
determined by calling @code{current-left-margin}. In no case does this
|
|
function delete non-whitespace. If @var{from} and @var{to} are omitted,
|
|
they default to the whole buffer.
|
|
@end defun
|
|
|
|
@defun indent-to-left-margin
|
|
This is the default @code{indent-line-function}, used in Fundamental
|
|
mode, Text mode, etc. Its effect is to adjust the indentation at the
|
|
beginning of the current line to the value specified by the variable
|
|
@code{left-margin}. This may involve either inserting or deleting
|
|
whitespace.
|
|
@end defun
|
|
|
|
@defvar left-margin
|
|
This variable specifies the base left margin column. In Fundamental
|
|
mode, @kbd{C-j} indents to this column. This variable automatically
|
|
becomes buffer-local when set in any fashion.
|
|
@end defvar
|
|
|
|
@defvar fill-nobreak-predicate
|
|
This variable gives major modes a way to specify not to break a line at
|
|
certain places. Its value should be a function. This function is
|
|
called during filling, with no arguments and with point located at the
|
|
place where a break is being considered. If the function returns
|
|
non-@code{nil}, then the line won't be broken there.
|
|
@end defvar
|
|
|
|
@node Adaptive Fill
|
|
@section Adaptive Fill Mode
|
|
@cindex Adaptive Fill mode
|
|
|
|
Adaptive Fill mode chooses a fill prefix automatically from the text
|
|
in each paragraph being filled.
|
|
|
|
@defopt adaptive-fill-mode
|
|
Adaptive Fill mode is enabled when this variable is non-@code{nil}.
|
|
It is @code{t} by default.
|
|
@end defopt
|
|
|
|
@defun fill-context-prefix from to
|
|
This function implements the heart of Adaptive Fill mode; it chooses a
|
|
fill prefix based on the text between @var{from} and @var{to}. It does
|
|
this by looking at the first two lines of the paragraph, based on the
|
|
variables described below.
|
|
@c The optional argument first-line-regexp is not documented
|
|
@c because it exists for internal purposes and might be eliminated
|
|
@c in the future.
|
|
@end defun
|
|
|
|
@defopt adaptive-fill-regexp
|
|
This variable holds a regular expression to control Adaptive Fill mode.
|
|
Adaptive Fill mode matches this regular expression against the text
|
|
starting after the left margin whitespace (if any) on a line; the
|
|
characters it matches are that line's candidate for the fill prefix.
|
|
@end defopt
|
|
|
|
@defopt adaptive-fill-first-line-regexp
|
|
In a one-line paragraph, if the candidate fill prefix matches this
|
|
regular expression, or if it matches @code{comment-start-skip}, then it
|
|
is used---otherwise, spaces amounting to the same width are used
|
|
instead.
|
|
|
|
However, the fill prefix is never taken from a one-line paragraph
|
|
if it would act as a paragraph starter on subsequent lines.
|
|
@end defopt
|
|
|
|
@defopt adaptive-fill-function
|
|
You can specify more complex ways of choosing a fill prefix
|
|
automatically by setting this variable to a function. The function is
|
|
called when @code{adaptive-fill-regexp} does not match, with point after
|
|
the left margin of a line, and it should return the appropriate fill
|
|
prefix based on that line. If it returns @code{nil}, that means it sees
|
|
no fill prefix in that line.
|
|
@end defopt
|
|
|
|
@node Auto Filling
|
|
@comment node-name, next, previous, up
|
|
@section Auto Filling
|
|
@cindex filling, automatic
|
|
@cindex Auto Fill mode
|
|
|
|
Auto Fill mode is a minor mode that fills lines automatically as text
|
|
is inserted. This section describes the hook used by Auto Fill mode.
|
|
For a description of functions that you can call explicitly to fill and
|
|
justify existing text, see @ref{Filling}.
|
|
|
|
Auto Fill mode also enables the functions that change the margins and
|
|
justification style to refill portions of the text. @xref{Margins}.
|
|
|
|
@defvar auto-fill-function
|
|
The value of this variable should be a function (of no arguments) to be
|
|
called after self-inserting a character from the table
|
|
@code{auto-fill-chars}. It may be @code{nil}, in which case nothing
|
|
special is done in that case.
|
|
|
|
The value of @code{auto-fill-function} is @code{do-auto-fill} when
|
|
Auto-Fill mode is enabled. That is a function whose sole purpose is to
|
|
implement the usual strategy for breaking a line.
|
|
|
|
@quotation
|
|
In older Emacs versions, this variable was named @code{auto-fill-hook},
|
|
but since it is not called with the standard convention for hooks, it
|
|
was renamed to @code{auto-fill-function} in version 19.
|
|
@end quotation
|
|
@end defvar
|
|
|
|
@defvar normal-auto-fill-function
|
|
This variable specifies the function to use for
|
|
@code{auto-fill-function}, if and when Auto Fill is turned on. Major
|
|
modes can set buffer-local values for this variable to alter how Auto
|
|
Fill works.
|
|
@end defvar
|
|
|
|
@defvar auto-fill-chars
|
|
A char table of characters which invoke @code{auto-fill-function} when
|
|
self-inserted---space and newline in most language environments. They
|
|
have an entry @code{t} in the table.
|
|
@end defvar
|
|
|
|
@node Sorting
|
|
@section Sorting Text
|
|
@cindex sorting text
|
|
|
|
The sorting functions described in this section all rearrange text in
|
|
a buffer. This is in contrast to the function @code{sort}, which
|
|
rearranges the order of the elements of a list (@pxref{Rearrangement}).
|
|
The values returned by these functions are not meaningful.
|
|
|
|
@defun sort-subr reverse nextrecfun endrecfun &optional startkeyfun endkeyfun
|
|
This function is the general text-sorting routine that subdivides a
|
|
buffer into records and then sorts them. Most of the commands in this
|
|
section use this function.
|
|
|
|
To understand how @code{sort-subr} works, consider the whole accessible
|
|
portion of the buffer as being divided into disjoint pieces called
|
|
@dfn{sort records}. The records may or may not be contiguous, but they
|
|
must not overlap. A portion of each sort record (perhaps all of it) is
|
|
designated as the sort key. Sorting rearranges the records in order by
|
|
their sort keys.
|
|
|
|
Usually, the records are rearranged in order of ascending sort key.
|
|
If the first argument to the @code{sort-subr} function, @var{reverse},
|
|
is non-@code{nil}, the sort records are rearranged in order of
|
|
descending sort key.
|
|
|
|
The next four arguments to @code{sort-subr} are functions that are
|
|
called to move point across a sort record. They are called many times
|
|
from within @code{sort-subr}.
|
|
|
|
@enumerate
|
|
@item
|
|
@var{nextrecfun} is called with point at the end of a record. This
|
|
function moves point to the start of the next record. The first record
|
|
is assumed to start at the position of point when @code{sort-subr} is
|
|
called. Therefore, you should usually move point to the beginning of
|
|
the buffer before calling @code{sort-subr}.
|
|
|
|
This function can indicate there are no more sort records by leaving
|
|
point at the end of the buffer.
|
|
|
|
@item
|
|
@var{endrecfun} is called with point within a record. It moves point to
|
|
the end of the record.
|
|
|
|
@item
|
|
@var{startkeyfun} is called to move point from the start of a record to
|
|
the start of the sort key. This argument is optional; if it is omitted,
|
|
the whole record is the sort key. If supplied, the function should
|
|
either return a non-@code{nil} value to be used as the sort key, or
|
|
return @code{nil} to indicate that the sort key is in the buffer
|
|
starting at point. In the latter case, @var{endkeyfun} is called to
|
|
find the end of the sort key.
|
|
|
|
@item
|
|
@var{endkeyfun} is called to move point from the start of the sort key
|
|
to the end of the sort key. This argument is optional. If
|
|
@var{startkeyfun} returns @code{nil} and this argument is omitted (or
|
|
@code{nil}), then the sort key extends to the end of the record. There
|
|
is no need for @var{endkeyfun} if @var{startkeyfun} returns a
|
|
non-@code{nil} value.
|
|
@end enumerate
|
|
|
|
As an example of @code{sort-subr}, here is the complete function
|
|
definition for @code{sort-lines}:
|
|
|
|
@example
|
|
@group
|
|
;; @r{Note that the first two lines of doc string}
|
|
;; @r{are effectively one line when viewed by a user.}
|
|
(defun sort-lines (reverse beg end)
|
|
"Sort lines in region alphabetically;\
|
|
argument means descending order.
|
|
Called from a program, there are three arguments:
|
|
@end group
|
|
@group
|
|
REVERSE (non-nil means reverse order),\
|
|
BEG and END (region to sort).
|
|
The variable `sort-fold-case' determines\
|
|
whether alphabetic case affects
|
|
the sort order.
|
|
@end group
|
|
@group
|
|
(interactive "P\nr")
|
|
(save-excursion
|
|
(save-restriction
|
|
(narrow-to-region beg end)
|
|
(goto-char (point-min))
|
|
(sort-subr reverse 'forward-line 'end-of-line))))
|
|
@end group
|
|
@end example
|
|
|
|
Here @code{forward-line} moves point to the start of the next record,
|
|
and @code{end-of-line} moves point to the end of record. We do not pass
|
|
the arguments @var{startkeyfun} and @var{endkeyfun}, because the entire
|
|
record is used as the sort key.
|
|
|
|
The @code{sort-paragraphs} function is very much the same, except that
|
|
its @code{sort-subr} call looks like this:
|
|
|
|
@example
|
|
@group
|
|
(sort-subr reverse
|
|
(function
|
|
(lambda ()
|
|
(while (and (not (eobp))
|
|
(looking-at paragraph-separate))
|
|
(forward-line 1))))
|
|
'forward-paragraph)
|
|
@end group
|
|
@end example
|
|
|
|
Markers pointing into any sort records are left with no useful
|
|
position after @code{sort-subr} returns.
|
|
@end defun
|
|
|
|
@defopt sort-fold-case
|
|
If this variable is non-@code{nil}, @code{sort-subr} and the other
|
|
buffer sorting functions ignore case when comparing strings.
|
|
@end defopt
|
|
|
|
@deffn Command sort-regexp-fields reverse record-regexp key-regexp start end
|
|
This command sorts the region between @var{start} and @var{end}
|
|
alphabetically as specified by @var{record-regexp} and @var{key-regexp}.
|
|
If @var{reverse} is a negative integer, then sorting is in reverse
|
|
order.
|
|
|
|
Alphabetical sorting means that two sort keys are compared by
|
|
comparing the first characters of each, the second characters of each,
|
|
and so on. If a mismatch is found, it means that the sort keys are
|
|
unequal; the sort key whose character is less at the point of first
|
|
mismatch is the lesser sort key. The individual characters are compared
|
|
according to their numerical character codes in the Emacs character set.
|
|
|
|
The value of the @var{record-regexp} argument specifies how to divide
|
|
the buffer into sort records. At the end of each record, a search is
|
|
done for this regular expression, and the text that matches it is taken
|
|
as the next record. For example, the regular expression @samp{^.+$},
|
|
which matches lines with at least one character besides a newline, would
|
|
make each such line into a sort record. @xref{Regular Expressions}, for
|
|
a description of the syntax and meaning of regular expressions.
|
|
|
|
The value of the @var{key-regexp} argument specifies what part of each
|
|
record is the sort key. The @var{key-regexp} could match the whole
|
|
record, or only a part. In the latter case, the rest of the record has
|
|
no effect on the sorted order of records, but it is carried along when
|
|
the record moves to its new position.
|
|
|
|
The @var{key-regexp} argument can refer to the text matched by a
|
|
subexpression of @var{record-regexp}, or it can be a regular expression
|
|
on its own.
|
|
|
|
If @var{key-regexp} is:
|
|
|
|
@table @asis
|
|
@item @samp{\@var{digit}}
|
|
then the text matched by the @var{digit}th @samp{\(...\)} parenthesis
|
|
grouping in @var{record-regexp} is the sort key.
|
|
|
|
@item @samp{\&}
|
|
then the whole record is the sort key.
|
|
|
|
@item a regular expression
|
|
then @code{sort-regexp-fields} searches for a match for the regular
|
|
expression within the record. If such a match is found, it is the sort
|
|
key. If there is no match for @var{key-regexp} within a record then
|
|
that record is ignored, which means its position in the buffer is not
|
|
changed. (The other records may move around it.)
|
|
@end table
|
|
|
|
For example, if you plan to sort all the lines in the region by the
|
|
first word on each line starting with the letter @samp{f}, you should
|
|
set @var{record-regexp} to @samp{^.*$} and set @var{key-regexp} to
|
|
@samp{\<f\w*\>}. The resulting expression looks like this:
|
|
|
|
@example
|
|
@group
|
|
(sort-regexp-fields nil "^.*$" "\\<f\\w*\\>"
|
|
(region-beginning)
|
|
(region-end))
|
|
@end group
|
|
@end example
|
|
|
|
If you call @code{sort-regexp-fields} interactively, it prompts for
|
|
@var{record-regexp} and @var{key-regexp} in the minibuffer.
|
|
@end deffn
|
|
|
|
@deffn Command sort-lines reverse start end
|
|
This command alphabetically sorts lines in the region between
|
|
@var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort
|
|
is in reverse order.
|
|
@end deffn
|
|
|
|
@deffn Command sort-paragraphs reverse start end
|
|
This command alphabetically sorts paragraphs in the region between
|
|
@var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort
|
|
is in reverse order.
|
|
@end deffn
|
|
|
|
@deffn Command sort-pages reverse start end
|
|
This command alphabetically sorts pages in the region between
|
|
@var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort
|
|
is in reverse order.
|
|
@end deffn
|
|
|
|
@deffn Command sort-fields field start end
|
|
This command sorts lines in the region between @var{start} and
|
|
@var{end}, comparing them alphabetically by the @var{field}th field
|
|
of each line. Fields are separated by whitespace and numbered starting
|
|
from 1. If @var{field} is negative, sorting is by the
|
|
@w{@minus{}@var{field}th} field from the end of the line. This command
|
|
is useful for sorting tables.
|
|
@end deffn
|
|
|
|
@deffn Command sort-numeric-fields field start end
|
|
This command sorts lines in the region between @var{start} and
|
|
@var{end}, comparing them numerically by the @var{field}th field of each
|
|
line. The specified field must contain a number in each line of the
|
|
region. Fields are separated by whitespace and numbered starting from
|
|
1. If @var{field} is negative, sorting is by the
|
|
@w{@minus{}@var{field}th} field from the end of the line. This command
|
|
is useful for sorting tables.
|
|
@end deffn
|
|
|
|
@deffn Command sort-columns reverse &optional beg end
|
|
This command sorts the lines in the region between @var{beg} and
|
|
@var{end}, comparing them alphabetically by a certain range of columns.
|
|
The column positions of @var{beg} and @var{end} bound the range of
|
|
columns to sort on.
|
|
|
|
If @var{reverse} is non-@code{nil}, the sort is in reverse order.
|
|
|
|
One unusual thing about this command is that the entire line
|
|
containing position @var{beg}, and the entire line containing position
|
|
@var{end}, are included in the region sorted.
|
|
|
|
Note that @code{sort-columns} uses the @code{sort} utility program,
|
|
and so cannot work properly on text containing tab characters. Use
|
|
@kbd{M-x untabify} to convert tabs to spaces before sorting.
|
|
@end deffn
|
|
|
|
@node Columns
|
|
@comment node-name, next, previous, up
|
|
@section Counting Columns
|
|
@cindex columns
|
|
@cindex counting columns
|
|
@cindex horizontal position
|
|
|
|
The column functions convert between a character position (counting
|
|
characters from the beginning of the buffer) and a column position
|
|
(counting screen characters from the beginning of a line).
|
|
|
|
These functions count each character according to the number of
|
|
columns it occupies on the screen. This means control characters count
|
|
as occupying 2 or 4 columns, depending upon the value of
|
|
@code{ctl-arrow}, and tabs count as occupying a number of columns that
|
|
depends on the value of @code{tab-width} and on the column where the tab
|
|
begins. @xref{Usual Display}.
|
|
|
|
Column number computations ignore the width of the window and the
|
|
amount of horizontal scrolling. Consequently, a column value can be
|
|
arbitrarily high. The first (or leftmost) column is numbered 0. They
|
|
also ignore overlays and text properties, aside from invisibility.
|
|
|
|
@defun current-column
|
|
This function returns the horizontal position of point, measured in
|
|
columns, counting from 0 at the left margin. The column position is the
|
|
sum of the widths of all the displayed representations of the characters
|
|
between the start of the current line and point.
|
|
|
|
For an example of using @code{current-column}, see the description of
|
|
@code{count-lines} in @ref{Text Lines}.
|
|
@end defun
|
|
|
|
@defun move-to-column column &optional force
|
|
This function moves point to @var{column} in the current line. The
|
|
calculation of @var{column} takes into account the widths of the
|
|
displayed representations of the characters between the start of the
|
|
line and point.
|
|
|
|
If column @var{column} is beyond the end of the line, point moves to the
|
|
end of the line. If @var{column} is negative, point moves to the
|
|
beginning of the line.
|
|
|
|
If it is impossible to move to column @var{column} because that is in
|
|
the middle of a multicolumn character such as a tab, point moves to the
|
|
end of that character. However, if @var{force} is non-@code{nil}, and
|
|
@var{column} is in the middle of a tab, then @code{move-to-column}
|
|
converts the tab into spaces so that it can move precisely to column
|
|
@var{column}. Other multicolumn characters can cause anomalies despite
|
|
@var{force}, since there is no way to split them.
|
|
|
|
The argument @var{force} also has an effect if the line isn't long
|
|
enough to reach column @var{column}; if it is @code{t}, that means to
|
|
add whitespace at the end of the line to reach that column.
|
|
|
|
If @var{column} is not an integer, an error is signaled.
|
|
|
|
The return value is the column number actually moved to.
|
|
@end defun
|
|
|
|
@node Indentation
|
|
@section Indentation
|
|
@cindex indentation
|
|
|
|
The indentation functions are used to examine, move to, and change
|
|
whitespace that is at the beginning of a line. Some of the functions
|
|
can also change whitespace elsewhere on a line. Columns and indentation
|
|
count from zero at the left margin.
|
|
|
|
@menu
|
|
* Primitive Indent:: Functions used to count and insert indentation.
|
|
* Mode-Specific Indent:: Customize indentation for different modes.
|
|
* Region Indent:: Indent all the lines in a region.
|
|
* Relative Indent:: Indent the current line based on previous lines.
|
|
* Indent Tabs:: Adjustable, typewriter-like tab stops.
|
|
* Motion by Indent:: Move to first non-blank character.
|
|
@end menu
|
|
|
|
@node Primitive Indent
|
|
@subsection Indentation Primitives
|
|
|
|
This section describes the primitive functions used to count and
|
|
insert indentation. The functions in the following sections use these
|
|
primitives. @xref{Width}, for related functions.
|
|
|
|
@defun current-indentation
|
|
@comment !!Type Primitive Function
|
|
@comment !!SourceFile indent.c
|
|
This function returns the indentation of the current line, which is
|
|
the horizontal position of the first nonblank character. If the
|
|
contents are entirely blank, then this is the horizontal position of the
|
|
end of the line.
|
|
@end defun
|
|
|
|
@deffn Command indent-to column &optional minimum
|
|
@comment !!Type Primitive Function
|
|
@comment !!SourceFile indent.c
|
|
This function indents from point with tabs and spaces until @var{column}
|
|
is reached. If @var{minimum} is specified and non-@code{nil}, then at
|
|
least that many spaces are inserted even if this requires going beyond
|
|
@var{column}. Otherwise the function does nothing if point is already
|
|
beyond @var{column}. The value is the column at which the inserted
|
|
indentation ends.
|
|
|
|
The inserted whitespace characters inherit text properties from the
|
|
surrounding text (usually, from the preceding text only). @xref{Sticky
|
|
Properties}.
|
|
@end deffn
|
|
|
|
@defopt indent-tabs-mode
|
|
@comment !!SourceFile indent.c
|
|
If this variable is non-@code{nil}, indentation functions can insert
|
|
tabs as well as spaces. Otherwise, they insert only spaces. Setting
|
|
this variable automatically makes it buffer-local in the current buffer.
|
|
@end defopt
|
|
|
|
@node Mode-Specific Indent
|
|
@subsection Indentation Controlled by Major Mode
|
|
|
|
An important function of each major mode is to customize the @key{TAB}
|
|
key to indent properly for the language being edited. This section
|
|
describes the mechanism of the @key{TAB} key and how to control it.
|
|
The functions in this section return unpredictable values.
|
|
|
|
@defvar indent-line-function
|
|
This variable's value is the function to be used by @key{TAB} (and
|
|
various commands) to indent the current line. The command
|
|
@code{indent-according-to-mode} does no more than call this function.
|
|
|
|
In Lisp mode, the value is the symbol @code{lisp-indent-line}; in C
|
|
mode, @code{c-indent-line}; in Fortran mode, @code{fortran-indent-line}.
|
|
In Fundamental mode, Text mode, and many other modes with no standard
|
|
for indentation, the value is @code{indent-to-left-margin} (which is the
|
|
default value).
|
|
@end defvar
|
|
|
|
@deffn Command indent-according-to-mode
|
|
This command calls the function in @code{indent-line-function} to
|
|
indent the current line in a way appropriate for the current major mode.
|
|
@end deffn
|
|
|
|
@deffn Command indent-for-tab-command
|
|
This command calls the function in @code{indent-line-function} to indent
|
|
the current line; however, if that function is
|
|
@code{indent-to-left-margin}, @code{insert-tab} is called instead. (That
|
|
is a trivial command that inserts a tab character.)
|
|
@end deffn
|
|
|
|
@deffn Command newline-and-indent
|
|
@comment !!SourceFile simple.el
|
|
This function inserts a newline, then indents the new line (the one
|
|
following the newline just inserted) according to the major mode.
|
|
|
|
It does indentation by calling the current @code{indent-line-function}.
|
|
In programming language modes, this is the same thing @key{TAB} does,
|
|
but in some text modes, where @key{TAB} inserts a tab,
|
|
@code{newline-and-indent} indents to the column specified by
|
|
@code{left-margin}.
|
|
@end deffn
|
|
|
|
@deffn Command reindent-then-newline-and-indent
|
|
@comment !!SourceFile simple.el
|
|
This command reindents the current line, inserts a newline at point,
|
|
and then indents the new line (the one following the newline just
|
|
inserted).
|
|
|
|
This command does indentation on both lines according to the current
|
|
major mode, by calling the current value of @code{indent-line-function}.
|
|
In programming language modes, this is the same thing @key{TAB} does,
|
|
but in some text modes, where @key{TAB} inserts a tab,
|
|
@code{reindent-then-newline-and-indent} indents to the column specified
|
|
by @code{left-margin}.
|
|
@end deffn
|
|
|
|
@node Region Indent
|
|
@subsection Indenting an Entire Region
|
|
|
|
This section describes commands that indent all the lines in the
|
|
region. They return unpredictable values.
|
|
|
|
@deffn Command indent-region start end to-column
|
|
This command indents each nonblank line starting between @var{start}
|
|
(inclusive) and @var{end} (exclusive). If @var{to-column} is
|
|
@code{nil}, @code{indent-region} indents each nonblank line by calling
|
|
the current mode's indentation function, the value of
|
|
@code{indent-line-function}.
|
|
|
|
If @var{to-column} is non-@code{nil}, it should be an integer
|
|
specifying the number of columns of indentation; then this function
|
|
gives each line exactly that much indentation, by either adding or
|
|
deleting whitespace.
|
|
|
|
If there is a fill prefix, @code{indent-region} indents each line
|
|
by making it start with the fill prefix.
|
|
@end deffn
|
|
|
|
@defvar indent-region-function
|
|
The value of this variable is a function that can be used by
|
|
@code{indent-region} as a short cut. It should take two arguments, the
|
|
start and end of the region. You should design the function so
|
|
that it will produce the same results as indenting the lines of the
|
|
region one by one, but presumably faster.
|
|
|
|
If the value is @code{nil}, there is no short cut, and
|
|
@code{indent-region} actually works line by line.
|
|
|
|
A short-cut function is useful in modes such as C mode and Lisp mode,
|
|
where the @code{indent-line-function} must scan from the beginning of
|
|
the function definition: applying it to each line would be quadratic in
|
|
time. The short cut can update the scan information as it moves through
|
|
the lines indenting them; this takes linear time. In a mode where
|
|
indenting a line individually is fast, there is no need for a short cut.
|
|
|
|
@code{indent-region} with a non-@code{nil} argument @var{to-column} has
|
|
a different meaning and does not use this variable.
|
|
@end defvar
|
|
|
|
@deffn Command indent-rigidly start end count
|
|
@comment !!SourceFile indent.el
|
|
This command indents all lines starting between @var{start}
|
|
(inclusive) and @var{end} (exclusive) sideways by @var{count} columns.
|
|
This ``preserves the shape'' of the affected region, moving it as a
|
|
rigid unit. Consequently, this command is useful not only for indenting
|
|
regions of unindented text, but also for indenting regions of formatted
|
|
code.
|
|
|
|
For example, if @var{count} is 3, this command adds 3 columns of
|
|
indentation to each of the lines beginning in the region specified.
|
|
|
|
In Mail mode, @kbd{C-c C-y} (@code{mail-yank-original}) uses
|
|
@code{indent-rigidly} to indent the text copied from the message being
|
|
replied to.
|
|
@end deffn
|
|
|
|
@defun indent-code-rigidly start end columns &optional nochange-regexp
|
|
This is like @code{indent-rigidly}, except that it doesn't alter lines
|
|
that start within strings or comments.
|
|
|
|
In addition, it doesn't alter a line if @var{nochange-regexp} matches at
|
|
the beginning of the line (if @var{nochange-regexp} is non-@code{nil}).
|
|
@end defun
|
|
|
|
@node Relative Indent
|
|
@subsection Indentation Relative to Previous Lines
|
|
|
|
This section describes two commands that indent the current line
|
|
based on the contents of previous lines.
|
|
|
|
@deffn Command indent-relative &optional unindented-ok
|
|
This command inserts whitespace at point, extending to the same
|
|
column as the next @dfn{indent point} of the previous nonblank line. An
|
|
indent point is a non-whitespace character following whitespace. The
|
|
next indent point is the first one at a column greater than the current
|
|
column of point. For example, if point is underneath and to the left of
|
|
the first non-blank character of a line of text, it moves to that column
|
|
by inserting whitespace.
|
|
|
|
If the previous nonblank line has no next indent point (i.e., none at a
|
|
great enough column position), @code{indent-relative} either does
|
|
nothing (if @var{unindented-ok} is non-@code{nil}) or calls
|
|
@code{tab-to-tab-stop}. Thus, if point is underneath and to the right
|
|
of the last column of a short line of text, this command ordinarily
|
|
moves point to the next tab stop by inserting whitespace.
|
|
|
|
The return value of @code{indent-relative} is unpredictable.
|
|
|
|
In the following example, point is at the beginning of the second
|
|
line:
|
|
|
|
@example
|
|
@group
|
|
This line is indented twelve spaces.
|
|
@point{}The quick brown fox jumped.
|
|
@end group
|
|
@end example
|
|
|
|
@noindent
|
|
Evaluation of the expression @code{(indent-relative nil)} produces the
|
|
following:
|
|
|
|
@example
|
|
@group
|
|
This line is indented twelve spaces.
|
|
@point{}The quick brown fox jumped.
|
|
@end group
|
|
@end example
|
|
|
|
In this next example, point is between the @samp{m} and @samp{p} of
|
|
@samp{jumped}:
|
|
|
|
@example
|
|
@group
|
|
This line is indented twelve spaces.
|
|
The quick brown fox jum@point{}ped.
|
|
@end group
|
|
@end example
|
|
|
|
@noindent
|
|
Evaluation of the expression @code{(indent-relative nil)} produces the
|
|
following:
|
|
|
|
@example
|
|
@group
|
|
This line is indented twelve spaces.
|
|
The quick brown fox jum @point{}ped.
|
|
@end group
|
|
@end example
|
|
@end deffn
|
|
|
|
@deffn Command indent-relative-maybe
|
|
@comment !!SourceFile indent.el
|
|
This command indents the current line like the previous nonblank line,
|
|
by calling @code{indent-relative} with @code{t} as the
|
|
@var{unindented-ok} argument. The return value is unpredictable.
|
|
|
|
If the previous nonblank line has no indent points beyond the current
|
|
column, this command does nothing.
|
|
@end deffn
|
|
|
|
@node Indent Tabs
|
|
@comment node-name, next, previous, up
|
|
@subsection Adjustable ``Tab Stops''
|
|
@cindex tabs stops for indentation
|
|
|
|
This section explains the mechanism for user-specified ``tab stops''
|
|
and the mechanisms that use and set them. The name ``tab stops'' is
|
|
used because the feature is similar to that of the tab stops on a
|
|
typewriter. The feature works by inserting an appropriate number of
|
|
spaces and tab characters to reach the next tab stop column; it does not
|
|
affect the display of tab characters in the buffer (@pxref{Usual
|
|
Display}). Note that the @key{TAB} character as input uses this tab
|
|
stop feature only in a few major modes, such as Text mode.
|
|
|
|
@deffn Command tab-to-tab-stop
|
|
This command inserts spaces or tabs before point, up to the next tab
|
|
stop column defined by @code{tab-stop-list}. It searches the list for
|
|
an element greater than the current column number, and uses that element
|
|
as the column to indent to. It does nothing if no such element is
|
|
found.
|
|
@end deffn
|
|
|
|
@defopt tab-stop-list
|
|
This variable is the list of tab stop columns used by
|
|
@code{tab-to-tab-stops}. The elements should be integers in increasing
|
|
order. The tab stop columns need not be evenly spaced.
|
|
|
|
Use @kbd{M-x edit-tab-stops} to edit the location of tab stops
|
|
interactively.
|
|
@end defopt
|
|
|
|
@node Motion by Indent
|
|
@subsection Indentation-Based Motion Commands
|
|
|
|
These commands, primarily for interactive use, act based on the
|
|
indentation in the text.
|
|
|
|
@deffn Command back-to-indentation
|
|
@comment !!SourceFile simple.el
|
|
This command moves point to the first non-whitespace character in the
|
|
current line (which is the line in which point is located). It returns
|
|
@code{nil}.
|
|
@end deffn
|
|
|
|
@deffn Command backward-to-indentation &optional arg
|
|
@comment !!SourceFile simple.el
|
|
This command moves point backward @var{arg} lines and then to the
|
|
first nonblank character on that line. It returns @code{nil}.
|
|
If @var{arg} is omitted or @code{nil}, it defaults to 1.
|
|
@end deffn
|
|
|
|
@deffn Command forward-to-indentation &optional arg
|
|
@comment !!SourceFile simple.el
|
|
This command moves point forward @var{arg} lines and then to the first
|
|
nonblank character on that line. It returns @code{nil}.
|
|
If @var{arg} is omitted or @code{nil}, it defaults to 1.
|
|
@end deffn
|
|
|
|
@node Case Changes
|
|
@comment node-name, next, previous, up
|
|
@section Case Changes
|
|
@cindex case conversion in buffers
|
|
|
|
The case change commands described here work on text in the current
|
|
buffer. @xref{Case Conversion}, for case conversion functions that work
|
|
on strings and characters. @xref{Case Tables}, for how to customize
|
|
which characters are upper or lower case and how to convert them.
|
|
|
|
@deffn Command capitalize-region start end
|
|
This function capitalizes all words in the region defined by
|
|
@var{start} and @var{end}. To capitalize means to convert each word's
|
|
first character to upper case and convert the rest of each word to lower
|
|
case. The function returns @code{nil}.
|
|
|
|
If one end of the region is in the middle of a word, the part of the
|
|
word within the region is treated as an entire word.
|
|
|
|
When @code{capitalize-region} is called interactively, @var{start} and
|
|
@var{end} are point and the mark, with the smallest first.
|
|
|
|
@example
|
|
@group
|
|
---------- Buffer: foo ----------
|
|
This is the contents of the 5th foo.
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
|
|
@group
|
|
(capitalize-region 1 44)
|
|
@result{} nil
|
|
|
|
---------- Buffer: foo ----------
|
|
This Is The Contents Of The 5th Foo.
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
@end example
|
|
@end deffn
|
|
|
|
@deffn Command downcase-region start end
|
|
This function converts all of the letters in the region defined by
|
|
@var{start} and @var{end} to lower case. The function returns
|
|
@code{nil}.
|
|
|
|
When @code{downcase-region} is called interactively, @var{start} and
|
|
@var{end} are point and the mark, with the smallest first.
|
|
@end deffn
|
|
|
|
@deffn Command upcase-region start end
|
|
This function converts all of the letters in the region defined by
|
|
@var{start} and @var{end} to upper case. The function returns
|
|
@code{nil}.
|
|
|
|
When @code{upcase-region} is called interactively, @var{start} and
|
|
@var{end} are point and the mark, with the smallest first.
|
|
@end deffn
|
|
|
|
@deffn Command capitalize-word count
|
|
This function capitalizes @var{count} words after point, moving point
|
|
over as it does. To capitalize means to convert each word's first
|
|
character to upper case and convert the rest of each word to lower case.
|
|
If @var{count} is negative, the function capitalizes the
|
|
@minus{}@var{count} previous words but does not move point. The value
|
|
is @code{nil}.
|
|
|
|
If point is in the middle of a word, the part of the word before point
|
|
is ignored when moving forward. The rest is treated as an entire word.
|
|
|
|
When @code{capitalize-word} is called interactively, @var{count} is
|
|
set to the numeric prefix argument.
|
|
@end deffn
|
|
|
|
@deffn Command downcase-word count
|
|
This function converts the @var{count} words after point to all lower
|
|
case, moving point over as it does. If @var{count} is negative, it
|
|
converts the @minus{}@var{count} previous words but does not move point.
|
|
The value is @code{nil}.
|
|
|
|
When @code{downcase-word} is called interactively, @var{count} is set
|
|
to the numeric prefix argument.
|
|
@end deffn
|
|
|
|
@deffn Command upcase-word count
|
|
This function converts the @var{count} words after point to all upper
|
|
case, moving point over as it does. If @var{count} is negative, it
|
|
converts the @minus{}@var{count} previous words but does not move point.
|
|
The value is @code{nil}.
|
|
|
|
When @code{upcase-word} is called interactively, @var{count} is set to
|
|
the numeric prefix argument.
|
|
@end deffn
|
|
|
|
@node Text Properties
|
|
@section Text Properties
|
|
@cindex text properties
|
|
@cindex attributes of text
|
|
@cindex properties of text
|
|
|
|
Each character position in a buffer or a string can have a @dfn{text
|
|
property list}, much like the property list of a symbol (@pxref{Property
|
|
Lists}). The properties belong to a particular character at a
|
|
particular place, such as, the letter @samp{T} at the beginning of this
|
|
sentence or the first @samp{o} in @samp{foo}---if the same character
|
|
occurs in two different places, the two occurrences generally have
|
|
different properties.
|
|
|
|
Each property has a name and a value. Both of these can be any Lisp
|
|
object, but the name is normally a symbol. The usual way to access the
|
|
property list is to specify a name and ask what value corresponds to it.
|
|
|
|
If a character has a @code{category} property, we call it the
|
|
@dfn{category} of the character. It should be a symbol. The properties
|
|
of the symbol serve as defaults for the properties of the character.
|
|
|
|
Copying text between strings and buffers preserves the properties
|
|
along with the characters; this includes such diverse functions as
|
|
@code{substring}, @code{insert}, and @code{buffer-substring}.
|
|
|
|
@menu
|
|
* Examining Properties:: Looking at the properties of one character.
|
|
* Changing Properties:: Setting the properties of a range of text.
|
|
* Property Search:: Searching for where a property changes value.
|
|
* Special Properties:: Particular properties with special meanings.
|
|
* Format Properties:: Properties for representing formatting of text.
|
|
* Sticky Properties:: How inserted text gets properties from
|
|
neighboring text.
|
|
* Saving Properties:: Saving text properties in files, and reading
|
|
them back.
|
|
* Lazy Properties:: Computing text properties in a lazy fashion
|
|
only when text is examined.
|
|
* Clickable Text:: Using text properties to make regions of text
|
|
do something when you click on them.
|
|
* Fields:: The @code{field} property defines
|
|
fields within the buffer.
|
|
* Not Intervals:: Why text properties do not use
|
|
Lisp-visible text intervals.
|
|
@end menu
|
|
|
|
@node Examining Properties
|
|
@subsection Examining Text Properties
|
|
|
|
The simplest way to examine text properties is to ask for the value of
|
|
a particular property of a particular character. For that, use
|
|
@code{get-text-property}. Use @code{text-properties-at} to get the
|
|
entire property list of a character. @xref{Property Search}, for
|
|
functions to examine the properties of a number of characters at once.
|
|
|
|
These functions handle both strings and buffers. Keep in mind that
|
|
positions in a string start from 0, whereas positions in a buffer start
|
|
from 1.
|
|
|
|
@defun get-text-property pos prop &optional object
|
|
This function returns the value of the @var{prop} property of the
|
|
character after position @var{pos} in @var{object} (a buffer or
|
|
string). The argument @var{object} is optional and defaults to the
|
|
current buffer.
|
|
|
|
If there is no @var{prop} property strictly speaking, but the character
|
|
has a category that is a symbol, then @code{get-text-property} returns
|
|
the @var{prop} property of that symbol.
|
|
@end defun
|
|
|
|
@defun get-char-property position prop &optional object
|
|
This function is like @code{get-text-property}, except that it checks
|
|
overlays first and then text properties. @xref{Overlays}.
|
|
|
|
The argument @var{object} may be a string, a buffer, or a window. If it
|
|
is a window, then the buffer displayed in that window is used for text
|
|
properties and overlays, but only the overlays active for that window
|
|
are considered. If @var{object} is a buffer, then all overlays in that
|
|
buffer are considered, as well as text properties. If @var{object} is a
|
|
string, only text properties are considered, since strings never have
|
|
overlays.
|
|
@end defun
|
|
|
|
@defun get-char-property-and-overlay position prop &optional object
|
|
This is like @code{get-char-property}, but gives extra information
|
|
about the overlay that the property value comes from.
|
|
|
|
Its value is a cons cell whose @sc{car} is the property value, the
|
|
same value @code{get-char-property} would return with the same
|
|
arguments. Its @sc{cdr} is the overlay in which the property was
|
|
found, or @code{nil}, if it was found as a text property or not found
|
|
at all.
|
|
|
|
If @var{position} is at the end of @var{object}, both the @sc{car} and
|
|
the @sc{cdr} of the value are @code{nil}.
|
|
@end defun
|
|
|
|
@defvar char-property-alias-alist
|
|
This variable holds an alist which maps property names to a list of
|
|
alternative property names. If a character does not specify a direct
|
|
value for a property, the alternative property names are consulted in
|
|
order; the first non-@code{nil} value is used. This variable takes
|
|
precedence over @code{default-text-properties}, and @code{category}
|
|
properties take precedence over this variable.
|
|
@end defvar
|
|
|
|
@defun text-properties-at position &optional object
|
|
This function returns the entire property list of the character at
|
|
@var{position} in the string or buffer @var{object}. If @var{object} is
|
|
@code{nil}, it defaults to the current buffer.
|
|
@end defun
|
|
|
|
@defvar default-text-properties
|
|
This variable holds a property list giving default values for text
|
|
properties. Whenever a character does not specify a value for a
|
|
property, neither directly, through a category symbol, or through
|
|
@code{char-property-alias-alist}, the value stored in this list is
|
|
used instead. Here is an example:
|
|
|
|
@example
|
|
(setq default-text-properties '(foo 69)
|
|
char-property-alias-alist nil)
|
|
;; @r{Make sure character 1 has no properties of its own.}
|
|
(set-text-properties 1 2 nil)
|
|
;; @r{What we get, when we ask, is the default value.}
|
|
(get-text-property 1 'foo)
|
|
@result{} 69
|
|
@end example
|
|
@end defvar
|
|
|
|
@node Changing Properties
|
|
@subsection Changing Text Properties
|
|
|
|
The primitives for changing properties apply to a specified range of
|
|
text in a buffer or string. The function @code{set-text-properties}
|
|
(see end of section) sets the entire property list of the text in that
|
|
range; more often, it is useful to add, change, or delete just certain
|
|
properties specified by name.
|
|
|
|
Since text properties are considered part of the contents of the
|
|
buffer (or string), and can affect how a buffer looks on the screen,
|
|
any change in buffer text properties marks the buffer as modified.
|
|
Buffer text property changes are undoable also (@pxref{Undo}).
|
|
Positions in a string start from 0, whereas positions in a buffer
|
|
start from 1.
|
|
|
|
@defun put-text-property start end prop value &optional object
|
|
This function sets the @var{prop} property to @var{value} for the text
|
|
between @var{start} and @var{end} in the string or buffer @var{object}.
|
|
If @var{object} is @code{nil}, it defaults to the current buffer.
|
|
@end defun
|
|
|
|
@defun add-text-properties start end props &optional object
|
|
This function adds or overrides text properties for the text between
|
|
@var{start} and @var{end} in the string or buffer @var{object}. If
|
|
@var{object} is @code{nil}, it defaults to the current buffer.
|
|
|
|
The argument @var{props} specifies which properties to add. It should
|
|
have the form of a property list (@pxref{Property Lists}): a list whose
|
|
elements include the property names followed alternately by the
|
|
corresponding values.
|
|
|
|
The return value is @code{t} if the function actually changed some
|
|
property's value; @code{nil} otherwise (if @var{props} is @code{nil} or
|
|
its values agree with those in the text).
|
|
|
|
For example, here is how to set the @code{comment} and @code{face}
|
|
properties of a range of text:
|
|
|
|
@example
|
|
(add-text-properties @var{start} @var{end}
|
|
'(comment t face highlight))
|
|
@end example
|
|
@end defun
|
|
|
|
@defun remove-text-properties start end props &optional object
|
|
This function deletes specified text properties from the text between
|
|
@var{start} and @var{end} in the string or buffer @var{object}. If
|
|
@var{object} is @code{nil}, it defaults to the current buffer.
|
|
|
|
The argument @var{props} specifies which properties to delete. It
|
|
should have the form of a property list (@pxref{Property Lists}): a list
|
|
whose elements are property names alternating with corresponding values.
|
|
But only the names matter---the values that accompany them are ignored.
|
|
For example, here's how to remove the @code{face} property.
|
|
|
|
@example
|
|
(remove-text-properties @var{start} @var{end} '(face nil))
|
|
@end example
|
|
|
|
The return value is @code{t} if the function actually changed some
|
|
property's value; @code{nil} otherwise (if @var{props} is @code{nil} or
|
|
if no character in the specified text had any of those properties).
|
|
|
|
To remove all text properties from certain text, use
|
|
@code{set-text-properties} and specify @code{nil} for the new property
|
|
list.
|
|
@end defun
|
|
|
|
@defun remove-list-of-text-properties start end list-of-properties &optional object
|
|
Like @code{remove-list-properties} except that
|
|
@var{list-of-properties} is a list property names only, not an
|
|
alternating list of property values.
|
|
@end defun
|
|
|
|
@defun set-text-properties start end props &optional object
|
|
This function completely replaces the text property list for the text
|
|
between @var{start} and @var{end} in the string or buffer @var{object}.
|
|
If @var{object} is @code{nil}, it defaults to the current buffer.
|
|
|
|
The argument @var{props} is the new property list. It should be a list
|
|
whose elements are property names alternating with corresponding values.
|
|
|
|
After @code{set-text-properties} returns, all the characters in the
|
|
specified range have identical properties.
|
|
|
|
If @var{props} is @code{nil}, the effect is to get rid of all properties
|
|
from the specified range of text. Here's an example:
|
|
|
|
@example
|
|
(set-text-properties @var{start} @var{end} nil)
|
|
@end example
|
|
@end defun
|
|
|
|
The easiest way to make a string with text properties
|
|
is with @code{propertize}:
|
|
|
|
@defun propertize string &rest properties
|
|
@tindex propertize
|
|
This function returns a copy of @var{string} which has the text
|
|
properties @var{properties}. These properties apply to all the
|
|
characters in the string that is returned. Here is an example that
|
|
constructs a string with a @code{face} property and a @code{mouse-face}
|
|
property:
|
|
|
|
@smallexample
|
|
(propertize "foo" 'face 'italic
|
|
'mouse-face 'bold-italic)
|
|
@result{} #("foo" 0 3 (mouse-face bold-italic face italic))
|
|
@end smallexample
|
|
|
|
To put different properties on various parts of a string, you can
|
|
construct each part with @code{propertize} and then combine them with
|
|
@code{concat}:
|
|
|
|
@smallexample
|
|
(concat
|
|
(propertize "foo" 'face 'italic
|
|
'mouse-face 'bold-italic)
|
|
" and "
|
|
(propertize "bar" 'face 'italic
|
|
'mouse-face 'bold-italic))
|
|
@result{} #("foo and bar"
|
|
0 3 (face italic mouse-face bold-italic)
|
|
3 8 nil
|
|
8 11 (face italic mouse-face bold-italic))
|
|
@end smallexample
|
|
@end defun
|
|
|
|
See also the function @code{buffer-substring-no-properties}
|
|
(@pxref{Buffer Contents}) which copies text from the buffer
|
|
but does not copy its properties.
|
|
|
|
@node Property Search
|
|
@subsection Text Property Search Functions
|
|
|
|
In typical use of text properties, most of the time several or many
|
|
consecutive characters have the same value for a property. Rather than
|
|
writing your programs to examine characters one by one, it is much
|
|
faster to process chunks of text that have the same property value.
|
|
|
|
Here are functions you can use to do this. They use @code{eq} for
|
|
comparing property values. In all cases, @var{object} defaults to the
|
|
current buffer.
|
|
|
|
For high performance, it's very important to use the @var{limit}
|
|
argument to these functions, especially the ones that search for a
|
|
single property---otherwise, they may spend a long time scanning to the
|
|
end of the buffer, if the property you are interested in does not change.
|
|
|
|
These functions do not move point; instead, they return a position (or
|
|
@code{nil}). Remember that a position is always between two characters;
|
|
the position returned by these functions is between two characters with
|
|
different properties.
|
|
|
|
@defun next-property-change pos &optional object limit
|
|
The function scans the text forward from position @var{pos} in the
|
|
string or buffer @var{object} till it finds a change in some text
|
|
property, then returns the position of the change. In other words, it
|
|
returns the position of the first character beyond @var{pos} whose
|
|
properties are not identical to those of the character just after
|
|
@var{pos}.
|
|
|
|
If @var{limit} is non-@code{nil}, then the scan ends at position
|
|
@var{limit}. If there is no property change before that point,
|
|
@code{next-property-change} returns @var{limit}.
|
|
|
|
The value is @code{nil} if the properties remain unchanged all the way
|
|
to the end of @var{object} and @var{limit} is @code{nil}. If the value
|
|
is non-@code{nil}, it is a position greater than or equal to @var{pos}.
|
|
The value equals @var{pos} only when @var{limit} equals @var{pos}.
|
|
|
|
Here is an example of how to scan the buffer by chunks of text within
|
|
which all properties are constant:
|
|
|
|
@smallexample
|
|
(while (not (eobp))
|
|
(let ((plist (text-properties-at (point)))
|
|
(next-change
|
|
(or (next-property-change (point) (current-buffer))
|
|
(point-max))))
|
|
@r{Process text from point to @var{next-change}@dots{}}
|
|
(goto-char next-change)))
|
|
@end smallexample
|
|
@end defun
|
|
|
|
@defun next-single-property-change pos prop &optional object limit
|
|
The function scans the text forward from position @var{pos} in the
|
|
string or buffer @var{object} till it finds a change in the @var{prop}
|
|
property, then returns the position of the change. In other words, it
|
|
returns the position of the first character beyond @var{pos} whose
|
|
@var{prop} property differs from that of the character just after
|
|
@var{pos}.
|
|
|
|
If @var{limit} is non-@code{nil}, then the scan ends at position
|
|
@var{limit}. If there is no property change before that point,
|
|
@code{next-single-property-change} returns @var{limit}.
|
|
|
|
The value is @code{nil} if the property remains unchanged all the way to
|
|
the end of @var{object} and @var{limit} is @code{nil}. If the value is
|
|
non-@code{nil}, it is a position greater than or equal to @var{pos}; it
|
|
equals @var{pos} only if @var{limit} equals @var{pos}.
|
|
@end defun
|
|
|
|
@defun previous-property-change pos &optional object limit
|
|
This is like @code{next-property-change}, but scans back from @var{pos}
|
|
instead of forward. If the value is non-@code{nil}, it is a position
|
|
less than or equal to @var{pos}; it equals @var{pos} only if @var{limit}
|
|
equals @var{pos}.
|
|
@end defun
|
|
|
|
@defun previous-single-property-change pos prop &optional object limit
|
|
This is like @code{next-single-property-change}, but scans back from
|
|
@var{pos} instead of forward. If the value is non-@code{nil}, it is a
|
|
position less than or equal to @var{pos}; it equals @var{pos} only if
|
|
@var{limit} equals @var{pos}.
|
|
@end defun
|
|
|
|
@defun next-char-property-change pos &optional limit
|
|
This is like @code{next-property-change} except that it considers
|
|
overlay properties as well as text properties, and if no change is
|
|
found before the end of the buffer, it returns the maximum buffer
|
|
position rather than @code{nil} (in this sense, it resembles the
|
|
corresponding overlay function @code{next-overlay-change}, rather than
|
|
@code{next-property-change}). There is no @var{object} operand
|
|
because this function operates only on the current buffer. It returns
|
|
the next address at which either kind of property changes.
|
|
@end defun
|
|
|
|
@defun previous-char-property-change pos &optional limit
|
|
This is like @code{next-char-property-change}, but scans back from
|
|
@var{pos} instead of forward, and returns the minimum buffer
|
|
position if no change is found.
|
|
@end defun
|
|
|
|
@defun next-single-char-property-change pos prop &optional object limit
|
|
@tindex next-single-char-property-change
|
|
This is like @code{next-single-property-change} except that it
|
|
considers overlay properties as well as text properties, and if no
|
|
change is found before the end of the @var{object}, it returns the
|
|
maximum valid position in @var{object} rather than @code{nil}. Unlike
|
|
@code{next-char-property-change}, this function @emph{does} have an
|
|
@var{object} operand; if @var{object} is not a buffer, only
|
|
text-properties are considered.
|
|
@end defun
|
|
|
|
@defun previous-single-char-property-change pos prop &optional object limit
|
|
@tindex previous-single-char-property-change
|
|
This is like @code{next-single-char-property-change}, but scans back
|
|
from @var{pos} instead of forward, and returns the minimum valid
|
|
position in @var{object} if no change is found.
|
|
@end defun
|
|
|
|
@defun text-property-any start end prop value &optional object
|
|
This function returns non-@code{nil} if at least one character between
|
|
@var{start} and @var{end} has a property @var{prop} whose value is
|
|
@var{value}. More precisely, it returns the position of the first such
|
|
character. Otherwise, it returns @code{nil}.
|
|
|
|
The optional fifth argument, @var{object}, specifies the string or
|
|
buffer to scan. Positions are relative to @var{object}. The default
|
|
for @var{object} is the current buffer.
|
|
@end defun
|
|
|
|
@defun text-property-not-all start end prop value &optional object
|
|
This function returns non-@code{nil} if at least one character between
|
|
@var{start} and @var{end} does not have a property @var{prop} with value
|
|
@var{value}. More precisely, it returns the position of the first such
|
|
character. Otherwise, it returns @code{nil}.
|
|
|
|
The optional fifth argument, @var{object}, specifies the string or
|
|
buffer to scan. Positions are relative to @var{object}. The default
|
|
for @var{object} is the current buffer.
|
|
@end defun
|
|
|
|
@node Special Properties
|
|
@subsection Properties with Special Meanings
|
|
|
|
Here is a table of text property names that have special built-in
|
|
meanings. The following sections list a few additional special property
|
|
names that control filling and property inheritance. All other names
|
|
have no standard meaning, and you can use them as you like.
|
|
|
|
@table @code
|
|
@cindex category of text character
|
|
@kindex category @r{(text property)}
|
|
@item category
|
|
If a character has a @code{category} property, we call it the
|
|
@dfn{category} of the character. It should be a symbol. The properties
|
|
of the symbol serve as defaults for the properties of the character.
|
|
|
|
@item face
|
|
@cindex face codes of text
|
|
@kindex face @r{(text property)}
|
|
You can use the property @code{face} to control the font and color of
|
|
text. @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
|
|
Starting in Emacs 21, 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})} is equivalent to
|
|
@code{(:foreground @var{color-name})}, and likewise for the background.
|
|
@end itemize
|
|
|
|
You can use Font Lock Mode (@pxref{Font Lock Mode}), to dynamically
|
|
update @code{face} properties based on the contents of the text.
|
|
|
|
@item font-lock-face
|
|
@kindex font-lock-face @r{(text property)}
|
|
The @code{font-lock-face} property is the same in all respects as the
|
|
@code{face} property, but its state of activation is controlled by
|
|
@code{font-lock-mode}. This can be advantageous for special buffers
|
|
which are not intended to be user-editable, or for static areas of
|
|
text which are always fontified in the same way.
|
|
@xref{Precalculated Fontification}.
|
|
|
|
Strictly speaking, @code{font-lock-face} is not a built-in text
|
|
property; rather, it is implemented in Font Lock mode using
|
|
@code{char-property-alias-alist}. @xref{Examining Properties}.
|
|
|
|
This property is new in Emacs 21.4.
|
|
|
|
@item mouse-face
|
|
@kindex mouse-face @r{(text property)}
|
|
The property @code{mouse-face} is used instead of @code{face} when the
|
|
mouse is on or near the character. For this purpose, ``near'' means
|
|
that all text between the character and where the mouse is have the same
|
|
@code{mouse-face} property value.
|
|
|
|
@item fontified
|
|
@kindex fontified @r{(text property)}
|
|
This property, if non-@code{nil}, says that text in the buffer has
|
|
had faces assigned automatically by a feature such as Font-Lock mode.
|
|
@xref{Auto Faces}.
|
|
|
|
@item display
|
|
@kindex display @r{(text 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 narrow, or replaced with an image.
|
|
@xref{Display Property}.
|
|
|
|
@item help-echo
|
|
@kindex help-echo @r{(text property)}
|
|
@cindex tooltip
|
|
@anchor{Text help-echo}
|
|
If text has a string as its @code{help-echo} property, then when you
|
|
move the mouse onto that text, Emacs displays that string in the echo
|
|
area, or in the tooltip window (@pxref{Tooltips,,, emacs, The GNU Emacs
|
|
Manual}).
|
|
|
|
If the value of the @code{help-echo} property is a function, that
|
|
function is called with three arguments, @var{window}, @var{object} and
|
|
@var{position} and should return a help string or @var{nil} for
|
|
none. The first argument, @var{window} is the window in which
|
|
the help was found. The second, @var{object}, is the buffer, overlay or
|
|
string which had the @code{help-echo} property. The @var{position}
|
|
argument is as follows:
|
|
|
|
@itemize @bullet{}
|
|
@item
|
|
If @var{object} is a buffer, @var{pos} is the position in the buffer
|
|
where the @code{help-echo} text property was found.
|
|
@item
|
|
If @var{object} is an overlay, that overlay has a @code{help-echo}
|
|
property, and @var{pos} is the position in the overlay's buffer under
|
|
the mouse.
|
|
@item
|
|
If @var{object} is a string (an overlay string or a string displayed
|
|
with the @code{display} property), @var{pos} is the position in that
|
|
string under the mouse.
|
|
@end itemize
|
|
|
|
If the value of the @code{help-echo} property is neither a function nor
|
|
a string, it is evaluated to obtain a help string.
|
|
|
|
You can alter the way help text is displayed by setting the variable
|
|
@code{show-help-function} (@pxref{Help display}).
|
|
|
|
This feature is used in the mode line and for other active text.
|
|
|
|
@item keymap
|
|
@cindex keymap of character
|
|
@kindex keymap @r{(text property)}
|
|
The @code{keymap} property specifies an additional keymap for
|
|
commands. The property's value for the character before point applies
|
|
if it is non-@code{nil} and rear-sticky, and the property's value for
|
|
the character after point applies if it is non-@code{nil} and
|
|
front-sticky. (For mouse clicks, the position of the click is used
|
|
instead of the position of point.) If the property value is a symbol,
|
|
the symbol's function definition is used as the keymap.
|
|
|
|
When this keymap applies, it is used for key lookup before the minor
|
|
mode keymaps and before the buffer's local map. @xref{Active
|
|
Keymaps}.
|
|
|
|
@item local-map
|
|
@kindex local-map @r{(text property)}
|
|
This property works like @code{keymap} except that it specifies a
|
|
keymap to use @emph{instead of} the buffer's local map. For most
|
|
purposes (perhaps all purposes), the @code{keymap} is superior.
|
|
|
|
@item syntax-table
|
|
The @code{syntax-table} property overrides what the syntax table says
|
|
about this particular character. @xref{Syntax Properties}.
|
|
|
|
@item read-only
|
|
@cindex read-only character
|
|
@kindex read-only @r{(text property)}
|
|
If a character has the property @code{read-only}, then modifying that
|
|
character is not allowed. Any command that would do so gets an error,
|
|
@code{text-read-only}.
|
|
|
|
Insertion next to a read-only character is an error if inserting
|
|
ordinary text there would inherit the @code{read-only} property due to
|
|
stickiness. Thus, you can control permission to insert next to
|
|
read-only text by controlling the stickiness. @xref{Sticky Properties}.
|
|
|
|
Since changing properties counts as modifying the buffer, it is not
|
|
possible to remove a @code{read-only} property unless you know the
|
|
special trick: bind @code{inhibit-read-only} to a non-@code{nil} value
|
|
and then remove the property. @xref{Read Only Buffers}.
|
|
|
|
@item invisible
|
|
@kindex invisible @r{(text property)}
|
|
A non-@code{nil} @code{invisible} property can make a character invisible
|
|
on the screen. @xref{Invisible Text}, for details.
|
|
|
|
@item intangible
|
|
@kindex intangible @r{(text property)}
|
|
If a group of consecutive characters have equal and non-@code{nil}
|
|
@code{intangible} properties, then you cannot place point between them.
|
|
If you try to move point forward into the group, point actually moves to
|
|
the end of the group. If you try to move point backward into the group,
|
|
point actually moves to the start of the group.
|
|
|
|
When the variable @code{inhibit-point-motion-hooks} is non-@code{nil},
|
|
the @code{intangible} property is ignored.
|
|
|
|
@item field
|
|
@kindex field @r{(text property)}
|
|
Consecutive characters with the same @code{field} property constitute a
|
|
@dfn{field}. Some motion functions including @code{forward-word} and
|
|
@code{beginning-of-line} stop moving at a field boundary.
|
|
@xref{Fields}.
|
|
|
|
@item modification-hooks
|
|
@cindex change hooks for a character
|
|
@cindex hooks for changing a character
|
|
@kindex modification-hooks @r{(text property)}
|
|
If a character has the property @code{modification-hooks}, then its
|
|
value should be a list of functions; modifying that character calls all
|
|
of those functions. Each function receives two arguments: the beginning
|
|
and end of the part of the buffer being modified. Note that if a
|
|
particular modification hook function appears on several characters
|
|
being modified by a single primitive, you can't predict how many times
|
|
the function will be called.
|
|
|
|
@item insert-in-front-hooks
|
|
@itemx insert-behind-hooks
|
|
@kindex insert-in-front-hooks @r{(text property)}
|
|
@kindex insert-behind-hooks @r{(text property)}
|
|
The operation of inserting text in a buffer also calls the functions
|
|
listed in the @code{insert-in-front-hooks} property of the following
|
|
character and in the @code{insert-behind-hooks} property of the
|
|
preceding character. These functions receive two arguments, the
|
|
beginning and end of the inserted text. The functions are called
|
|
@emph{after} the actual insertion takes place.
|
|
|
|
See also @ref{Change Hooks}, for other hooks that are called
|
|
when you change text in a buffer.
|
|
|
|
@item point-entered
|
|
@itemx point-left
|
|
@cindex hooks for motion of point
|
|
@kindex point-entered @r{(text property)}
|
|
@kindex point-left @r{(text property)}
|
|
The special properties @code{point-entered} and @code{point-left}
|
|
record hook functions that report motion of point. Each time point
|
|
moves, Emacs compares these two property values:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
the @code{point-left} property of the character after the old location,
|
|
and
|
|
@item
|
|
the @code{point-entered} property of the character after the new
|
|
location.
|
|
@end itemize
|
|
|
|
@noindent
|
|
If these two values differ, each of them is called (if not @code{nil})
|
|
with two arguments: the old value of point, and the new one.
|
|
|
|
The same comparison is made for the characters before the old and new
|
|
locations. The result may be to execute two @code{point-left} functions
|
|
(which may be the same function) and/or two @code{point-entered}
|
|
functions (which may be the same function). In any case, all the
|
|
@code{point-left} functions are called first, followed by all the
|
|
@code{point-entered} functions.
|
|
|
|
It is possible with @code{char-after} to examine characters at various
|
|
buffer positions without moving point to those positions. Only an
|
|
actual change in the value of point runs these hook functions.
|
|
@end table
|
|
|
|
@defvar inhibit-point-motion-hooks
|
|
When this variable is non-@code{nil}, @code{point-left} and
|
|
@code{point-entered} hooks are not run, and the @code{intangible}
|
|
property has no effect. Do not set this variable globally; bind it with
|
|
@code{let}.
|
|
@end defvar
|
|
|
|
@defvar show-help-function
|
|
@tindex show-help-function
|
|
@anchor{Help display} If this variable is non-@code{nil}, it specifies a
|
|
function called to display help strings. These may be @code{help-echo}
|
|
properties, menu help strings (@pxref{Simple Menu Items},
|
|
@pxref{Extended Menu Items}), or tool bar help strings (@pxref{Tool
|
|
Bar}). The specified function is called with one argument, the help
|
|
string to display. Tooltip mode (@pxref{Tooltips,,, emacs, The GNU Emacs
|
|
Manual}) provides an example.
|
|
@end defvar
|
|
|
|
@node Format Properties
|
|
@subsection Formatted Text Properties
|
|
|
|
These text properties affect the behavior of the fill commands. They
|
|
are used for representing formatted text. @xref{Filling}, and
|
|
@ref{Margins}.
|
|
|
|
@table @code
|
|
@item hard
|
|
If a newline character has this property, it is a ``hard'' newline.
|
|
The fill commands do not alter hard newlines and do not move words
|
|
across them. However, this property takes effect only if the variable
|
|
@code{use-hard-newlines} is non-@code{nil}.
|
|
|
|
@item right-margin
|
|
This property specifies an extra right margin for filling this part of the
|
|
text.
|
|
|
|
@item left-margin
|
|
This property specifies an extra left margin for filling this part of the
|
|
text.
|
|
|
|
@item justification
|
|
This property specifies the style of justification for filling this part
|
|
of the text.
|
|
@end table
|
|
|
|
@node Sticky Properties
|
|
@subsection Stickiness of Text Properties
|
|
@cindex sticky text properties
|
|
@cindex inheritance of text properties
|
|
|
|
Self-inserting characters normally take on the same properties as the
|
|
preceding character. This is called @dfn{inheritance} of properties.
|
|
|
|
In a Lisp program, you can do insertion with inheritance or without,
|
|
depending on your choice of insertion primitive. The ordinary text
|
|
insertion functions such as @code{insert} do not inherit any properties.
|
|
They insert text with precisely the properties of the string being
|
|
inserted, and no others. This is correct for programs that copy text
|
|
from one context to another---for example, into or out of the kill ring.
|
|
To insert with inheritance, use the special primitives described in this
|
|
section. Self-inserting characters inherit properties because they work
|
|
using these primitives.
|
|
|
|
When you do insertion with inheritance, @emph{which} properties are
|
|
inherited, and from where, depends on which properties are @dfn{sticky}.
|
|
Insertion after a character inherits those of its properties that are
|
|
@dfn{rear-sticky}. Insertion before a character inherits those of its
|
|
properties that are @dfn{front-sticky}. When both sides offer different
|
|
sticky values for the same property, the previous character's value
|
|
takes precedence.
|
|
|
|
By default, a text property is rear-sticky but not front-sticky; thus,
|
|
the default is to inherit all the properties of the preceding character,
|
|
and nothing from the following character.
|
|
|
|
You can control the stickiness of various text properties with two
|
|
specific text properties, @code{front-sticky} and @code{rear-nonsticky},
|
|
and with the variable @code{text-property-default-nonsticky}. You can
|
|
use the variable to specify a different default for a given property.
|
|
You can use those two text properties to make any specific properties
|
|
sticky or nonsticky in any particular part of the text.
|
|
|
|
If a character's @code{front-sticky} property is @code{t}, then all
|
|
its properties are front-sticky. If the @code{front-sticky} property is
|
|
a list, then the sticky properties of the character are those whose
|
|
names are in the list. For example, if a character has a
|
|
@code{front-sticky} property whose value is @code{(face read-only)},
|
|
then insertion before the character can inherit its @code{face} property
|
|
and its @code{read-only} property, but no others.
|
|
|
|
The @code{rear-nonsticky} property works the opposite way. Most
|
|
properties are rear-sticky by default, so the @code{rear-nonsticky}
|
|
property says which properties are @emph{not} rear-sticky. If a
|
|
character's @code{rear-nonsticky} property is @code{t}, then none of its
|
|
properties are rear-sticky. If the @code{rear-nonsticky} property is a
|
|
list, properties are rear-sticky @emph{unless} their names are in the
|
|
list.
|
|
|
|
@defvar text-property-default-nonsticky
|
|
@tindex text-property-default-nonsticky
|
|
This variable holds an alist which defines the default rear-stickiness
|
|
of various text properties. Each element has the form
|
|
@code{(@var{property} . @var{nonstickiness})}, and it defines the
|
|
stickiness of a particular text property, @var{property}.
|
|
|
|
If @var{nonstickiness} is non-@code{nil}, this means that the property
|
|
@var{property} is rear-nonsticky by default. Since all properties are
|
|
front-nonsticky by default, this makes @var{property} nonsticky in both
|
|
directions by default.
|
|
|
|
The text properties @code{front-sticky} and @code{rear-nonsticky}, when
|
|
used, take precedence over the default @var{nonstickiness} specified in
|
|
@code{text-property-default-nonsticky}.
|
|
@end defvar
|
|
|
|
Here are the functions that insert text with inheritance of properties:
|
|
|
|
@defun insert-and-inherit &rest strings
|
|
Insert the strings @var{strings}, just like the function @code{insert},
|
|
but inherit any sticky properties from the adjoining text.
|
|
@end defun
|
|
|
|
@defun insert-before-markers-and-inherit &rest strings
|
|
Insert the strings @var{strings}, just like the function
|
|
@code{insert-before-markers}, but inherit any sticky properties from the
|
|
adjoining text.
|
|
@end defun
|
|
|
|
@xref{Insertion}, for the ordinary insertion functions which do not
|
|
inherit.
|
|
|
|
@node Saving Properties
|
|
@subsection Saving Text Properties in Files
|
|
@cindex text properties in files
|
|
@cindex saving text properties
|
|
|
|
You can save text properties in files (along with the text itself),
|
|
and restore the same text properties when visiting or inserting the
|
|
files, using these two hooks:
|
|
|
|
@defvar write-region-annotate-functions
|
|
This variable's value is a list of functions for @code{write-region} to
|
|
run to encode text properties in some fashion as annotations to the text
|
|
being written in the file. @xref{Writing to Files}.
|
|
|
|
Each function in the list is called with two arguments: the start and
|
|
end of the region to be written. These functions should not alter the
|
|
contents of the buffer. Instead, they should return lists indicating
|
|
annotations to write in the file in addition to the text in the
|
|
buffer.
|
|
|
|
Each function should return a list of elements of the form
|
|
@code{(@var{position} . @var{string})}, where @var{position} is an
|
|
integer specifying the relative position within the text to be written,
|
|
and @var{string} is the annotation to add there.
|
|
|
|
Each list returned by one of these functions must be already sorted in
|
|
increasing order by @var{position}. If there is more than one function,
|
|
@code{write-region} merges the lists destructively into one sorted list.
|
|
|
|
When @code{write-region} actually writes the text from the buffer to the
|
|
file, it intermixes the specified annotations at the corresponding
|
|
positions. All this takes place without modifying the buffer.
|
|
@end defvar
|
|
|
|
@defvar after-insert-file-functions
|
|
This variable holds a list of functions for @code{insert-file-contents}
|
|
to call after inserting a file's contents. These functions should scan
|
|
the inserted text for annotations, and convert them to the text
|
|
properties they stand for.
|
|
|
|
Each function receives one argument, the length of the inserted text;
|
|
point indicates the start of that text. The function should scan that
|
|
text for annotations, delete them, and create the text properties that
|
|
the annotations specify. The function should return the updated length
|
|
of the inserted text, as it stands after those changes. The value
|
|
returned by one function becomes the argument to the next function.
|
|
|
|
These functions should always return with point at the beginning of
|
|
the inserted text.
|
|
|
|
The intended use of @code{after-insert-file-functions} is for converting
|
|
some sort of textual annotations into actual text properties. But other
|
|
uses may be possible.
|
|
@end defvar
|
|
|
|
We invite users to write Lisp programs to store and retrieve text
|
|
properties in files, using these hooks, and thus to experiment with
|
|
various data formats and find good ones. Eventually we hope users
|
|
will produce good, general extensions we can install in Emacs.
|
|
|
|
We suggest not trying to handle arbitrary Lisp objects as text property
|
|
names or values---because a program that general is probably difficult
|
|
to write, and slow. Instead, choose a set of possible data types that
|
|
are reasonably flexible, and not too hard to encode.
|
|
|
|
@xref{Format Conversion}, for a related feature.
|
|
|
|
@c ??? In next edition, merge this info Format Conversion.
|
|
|
|
@node Lazy Properties
|
|
@subsection Lazy Computation of Text Properties
|
|
|
|
Instead of computing text properties for all the text in the buffer,
|
|
you can arrange to compute the text properties for parts of the text
|
|
when and if something depends on them.
|
|
|
|
The primitive that extracts text from the buffer along with its
|
|
properties is @code{buffer-substring}. Before examining the properties,
|
|
this function runs the abnormal hook @code{buffer-access-fontify-functions}.
|
|
|
|
@defvar buffer-access-fontify-functions
|
|
This variable holds a list of functions for computing text properties.
|
|
Before @code{buffer-substring} copies the text and text properties for a
|
|
portion of the buffer, it calls all the functions in this list. Each of
|
|
the functions receives two arguments that specify the range of the
|
|
buffer being accessed. (The buffer itself is always the current
|
|
buffer.)
|
|
@end defvar
|
|
|
|
The function @code{buffer-substring-no-properties} does not call these
|
|
functions, since it ignores text properties anyway.
|
|
|
|
In order to prevent the hook functions from being called more than
|
|
once for the same part of the buffer, you can use the variable
|
|
@code{buffer-access-fontified-property}.
|
|
|
|
@defvar buffer-access-fontified-property
|
|
If this value's variable is non-@code{nil}, it is a symbol which is used
|
|
as a text property name. A non-@code{nil} value for that text property
|
|
means, ``the other text properties for this character have already been
|
|
computed.''
|
|
|
|
If all the characters in the range specified for @code{buffer-substring}
|
|
have a non-@code{nil} value for this property, @code{buffer-substring}
|
|
does not call the @code{buffer-access-fontify-functions} functions. It
|
|
assumes these characters already have the right text properties, and
|
|
just copies the properties they already have.
|
|
|
|
The normal way to use this feature is that the
|
|
@code{buffer-access-fontify-functions} functions add this property, as
|
|
well as others, to the characters they operate on. That way, they avoid
|
|
being called over and over for the same text.
|
|
@end defvar
|
|
|
|
@node Clickable Text
|
|
@subsection Defining Clickable Text
|
|
@cindex clickable text
|
|
|
|
There are two ways to set up @dfn{clickable text} in a buffer.
|
|
There are typically two parts of this: to make the text highlight
|
|
when the mouse is over it, and to make a mouse button do something
|
|
when you click it on that part of the text.
|
|
|
|
Highlighting is done with the @code{mouse-face} text property.
|
|
Here is an example of how Dired does it:
|
|
|
|
@smallexample
|
|
(condition-case nil
|
|
(if (dired-move-to-filename)
|
|
(put-text-property (point)
|
|
(save-excursion
|
|
(dired-move-to-end-of-filename)
|
|
(point))
|
|
'mouse-face 'highlight))
|
|
(error nil))
|
|
@end smallexample
|
|
|
|
@noindent
|
|
The first two arguments to @code{put-text-property} specify the
|
|
beginning and end of the text.
|
|
|
|
The usual way to make the mouse do something when you click it
|
|
on this text is to define @code{mouse-2} in the major mode's
|
|
keymap. The job of checking whether the click was on clickable text
|
|
is done by the command definition. Here is how Dired does it:
|
|
|
|
@smallexample
|
|
(defun dired-mouse-find-file-other-window (event)
|
|
"In dired, visit the file or directory name you click on."
|
|
(interactive "e")
|
|
(let (file)
|
|
(save-excursion
|
|
(set-buffer (window-buffer (posn-window (event-end event))))
|
|
(save-excursion
|
|
(goto-char (posn-point (event-end event)))
|
|
(setq file (dired-get-filename))))
|
|
(select-window (posn-window (event-end event)))
|
|
(find-file-other-window (file-name-sans-versions file t))))
|
|
@end smallexample
|
|
|
|
@noindent
|
|
The reason for the outer @code{save-excursion} construct is to avoid
|
|
changing the current buffer; the reason for the inner one is to avoid
|
|
permanently altering point in the buffer you click on. In this case,
|
|
Dired uses the function @code{dired-get-filename} to determine which
|
|
file to visit, based on the position found in the event.
|
|
|
|
Instead of defining a mouse command for the major mode, you can define
|
|
a key binding for the clickable text itself, using the @code{keymap}
|
|
text property:
|
|
|
|
@example
|
|
(let ((map (make-sparse-keymap)))
|
|
(define-key map [mouse-2] 'operate-this-button)
|
|
(put-text-property (point)
|
|
(save-excursion
|
|
(dired-move-to-end-of-filename)
|
|
(point))
|
|
'keymap map))
|
|
@end example
|
|
|
|
@noindent
|
|
This method makes it possible to define different commands for various
|
|
clickable pieces of text. Also, the major mode definition (or the
|
|
global definition) remains available for the rest of the text in the
|
|
buffer.
|
|
|
|
@node Fields
|
|
@subsection Defining and Using Fields
|
|
@cindex fields
|
|
|
|
A field is a range of consecutive characters in the buffer that are
|
|
identified by having the same value (comparing with @code{eq}) of the
|
|
@code{field} property (either a text-property or an overlay property).
|
|
This section describes special functions that are available for
|
|
operating on fields.
|
|
|
|
You specify a field with a buffer position, @var{pos}. We think of
|
|
each field as containing a range of buffer positions, so the position
|
|
you specify stands for the field containing that position.
|
|
|
|
When the characters before and after @var{pos} are part of the same
|
|
field, there is no doubt which field contains @var{pos}: the one those
|
|
characters both belong to. When @var{pos} is at a boundary between
|
|
fields, which field it belongs to depends on the stickiness of the
|
|
@code{field} properties of the two surrounding characters (@pxref{Sticky
|
|
Properties}). The field whose property would be inherited by text
|
|
inserted at @var{pos} is the field that contains @var{pos}.
|
|
|
|
There is an anomalous case where newly inserted text at @var{pos}
|
|
would not inherit the @code{field} property from either side. This
|
|
happens if the previous character's @code{field} property is not
|
|
rear-sticky, and the following character's @code{field} property is not
|
|
front-sticky. In this case, @var{pos} belongs to neither the preceding
|
|
field nor the following field; the field functions treat it as belonging
|
|
to an empty field whose beginning and end are both at @var{pos}.
|
|
|
|
In all of these functions, if @var{pos} is omitted or @code{nil}, the
|
|
value of point is used by default.
|
|
|
|
@defun field-beginning &optional pos escape-from-edge limit
|
|
@tindex field-beginning
|
|
This function returns the beginning of the field specified by @var{pos}.
|
|
|
|
If @var{pos} is at the beginning of its field, and
|
|
@var{escape-from-edge} is non-@code{nil}, then the return value is
|
|
always the beginning of the preceding field that @emph{ends} at @var{pos},
|
|
regardless of the stickiness of the @code{field} properties around
|
|
@var{pos}.
|
|
|
|
If @var{limit} is non-@code{nil}, it is a buffer position; if the
|
|
beginning of the field is before @var{limit}, then @var{limit} will be
|
|
returned instead.
|
|
@end defun
|
|
|
|
@defun field-end &optional pos escape-from-edge limit
|
|
@tindex field-end
|
|
This function returns the end of the field specified by @var{pos}.
|
|
|
|
If @var{pos} is at the end of its field, and @var{escape-from-edge} is
|
|
non-@code{nil}, then the return value is always the end of the following
|
|
field that @emph{begins} at @var{pos}, regardless of the stickiness of
|
|
the @code{field} properties around @var{pos}.
|
|
|
|
If @var{limit} is non-@code{nil}, it is a buffer position; if the end
|
|
of the field is after @var{limit}, then @var{limit} will be returned
|
|
instead.
|
|
@end defun
|
|
|
|
@defun field-string &optional pos
|
|
@tindex field-string
|
|
This function returns the contents of the field specified by @var{pos},
|
|
as a string.
|
|
@end defun
|
|
|
|
@defun field-string-no-properties &optional pos
|
|
@tindex field-string-no-properties
|
|
This function returns the contents of the field specified by @var{pos},
|
|
as a string, discarding text properties.
|
|
@end defun
|
|
|
|
@defun delete-field &optional pos
|
|
@tindex delete-field
|
|
This function deletes the text of the field specified by @var{pos}.
|
|
@end defun
|
|
|
|
@defun constrain-to-field new-pos old-pos &optional escape-from-edge only-in-line inhibit-capture-property
|
|
@tindex constrain-to-field
|
|
This function ``constrains'' @var{new-pos} to the field that
|
|
@var{old-pos} belongs to---in other words, it returns the position
|
|
closest to @var{new-pos} that is in the same field as @var{old-pos}.
|
|
|
|
If @var{new-pos} is @code{nil}, then @code{constrain-to-field} uses
|
|
the value of point instead, and moves point to the resulting position.
|
|
|
|
If @var{old-pos} is at the boundary of two fields, then the acceptable
|
|
positions for @var{new-pos} depend on the value of the optional argument
|
|
@var{escape-from-edge}. If @var{escape-from-edge} is @code{nil}, then
|
|
@var{new-pos} is constrained to the field that has the same @code{field}
|
|
property (either a text-property or an overlay property) that new
|
|
characters inserted at @var{old-pos} would get. (This depends on the
|
|
stickiness of the @code{field} property for the characters before and
|
|
after @var{old-pos}.) If @var{escape-from-edge} is non-@code{nil},
|
|
@var{new-pos} is constrained to the union of the two adjacent fields.
|
|
Additionally, if two fields are separated by another field with the
|
|
special value @code{boundary}, then any point within this special field
|
|
is also considered to be ``on the boundary.''
|
|
|
|
If the optional argument @var{only-in-line} is non-@code{nil}, and
|
|
constraining @var{new-pos} in the usual way would move it to a different
|
|
line, @var{new-pos} is returned unconstrained. This used in commands
|
|
that move by line, such as @code{next-line} and
|
|
@code{beginning-of-line}, so that they respect field boundaries only in
|
|
the case where they can still move to the right line.
|
|
|
|
If the optional argument @var{inhibit-capture-property} is
|
|
non-@code{nil}, and @var{old-pos} has a non-@code{nil} property of that
|
|
name, then any field boundaries are ignored.
|
|
|
|
You can cause @code{constrain-to-field} to ignore all field boundaries
|
|
(and so never constrain anything) by binding the variable
|
|
@code{inhibit-field-text-motion} to a non-@code{nil} value.
|
|
@end defun
|
|
|
|
@node Not Intervals
|
|
@subsection Why Text Properties are not Intervals
|
|
@cindex intervals
|
|
|
|
Some editors that support adding attributes to text in the buffer do
|
|
so by letting the user specify ``intervals'' within the text, and adding
|
|
the properties to the intervals. Those editors permit the user or the
|
|
programmer to determine where individual intervals start and end. We
|
|
deliberately provided a different sort of interface in Emacs Lisp to
|
|
avoid certain paradoxical behavior associated with text modification.
|
|
|
|
If the actual subdivision into intervals is meaningful, that means you
|
|
can distinguish between a buffer that is just one interval with a
|
|
certain property, and a buffer containing the same text subdivided into
|
|
two intervals, both of which have that property.
|
|
|
|
Suppose you take the buffer with just one interval and kill part of
|
|
the text. The text remaining in the buffer is one interval, and the
|
|
copy in the kill ring (and the undo list) becomes a separate interval.
|
|
Then if you yank back the killed text, you get two intervals with the
|
|
same properties. Thus, editing does not preserve the distinction
|
|
between one interval and two.
|
|
|
|
Suppose we ``fix'' this problem by coalescing the two intervals when
|
|
the text is inserted. That works fine if the buffer originally was a
|
|
single interval. But suppose instead that we have two adjacent
|
|
intervals with the same properties, and we kill the text of one interval
|
|
and yank it back. The same interval-coalescence feature that rescues
|
|
the other case causes trouble in this one: after yanking, we have just
|
|
one interval. One again, editing does not preserve the distinction
|
|
between one interval and two.
|
|
|
|
Insertion of text at the border between intervals also raises
|
|
questions that have no satisfactory answer.
|
|
|
|
However, it is easy to arrange for editing to behave consistently for
|
|
questions of the form, ``What are the properties of this character?''
|
|
So we have decided these are the only questions that make sense; we have
|
|
not implemented asking questions about where intervals start or end.
|
|
|
|
In practice, you can usually use the text property search functions in
|
|
place of explicit interval boundaries. You can think of them as finding
|
|
the boundaries of intervals, assuming that intervals are always
|
|
coalesced whenever possible. @xref{Property Search}.
|
|
|
|
Emacs also provides explicit intervals as a presentation feature; see
|
|
@ref{Overlays}.
|
|
|
|
@node Substitution
|
|
@section Substituting for a Character Code
|
|
|
|
The following functions replace characters within a specified region
|
|
based on their character codes.
|
|
|
|
@defun subst-char-in-region start end old-char new-char &optional noundo
|
|
@cindex replace characters
|
|
This function replaces all occurrences of the character @var{old-char}
|
|
with the character @var{new-char} in the region of the current buffer
|
|
defined by @var{start} and @var{end}.
|
|
|
|
@cindex undo avoidance
|
|
If @var{noundo} is non-@code{nil}, then @code{subst-char-in-region} does
|
|
not record the change for undo and does not mark the buffer as modified.
|
|
This was useful for controlling the old selective display feature
|
|
(@pxref{Selective Display}).
|
|
|
|
@code{subst-char-in-region} does not move point and returns
|
|
@code{nil}.
|
|
|
|
@example
|
|
@group
|
|
---------- Buffer: foo ----------
|
|
This is the contents of the buffer before.
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
|
|
@group
|
|
(subst-char-in-region 1 20 ?i ?X)
|
|
@result{} nil
|
|
|
|
---------- Buffer: foo ----------
|
|
ThXs Xs the contents of the buffer before.
|
|
---------- Buffer: foo ----------
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun translate-region start end table
|
|
This function applies a translation table to the characters in the
|
|
buffer between positions @var{start} and @var{end}.
|
|
|
|
The translation table @var{table} is a string; @code{(aref @var{table}
|
|
@var{ochar})} gives the translated character corresponding to
|
|
@var{ochar}. If the length of @var{table} is less than 256, any
|
|
characters with codes larger than the length of @var{table} are not
|
|
altered by the translation.
|
|
|
|
The return value of @code{translate-region} is the number of
|
|
characters that were actually changed by the translation. This does
|
|
not count characters that were mapped into themselves in the
|
|
translation table.
|
|
@end defun
|
|
|
|
@node Registers
|
|
@section Registers
|
|
@cindex registers
|
|
|
|
A register is a sort of variable used in Emacs editing that can hold a
|
|
variety of different kinds of values. Each register is named by a
|
|
single character. All @acronym{ASCII} characters and their meta variants
|
|
(but with the exception of @kbd{C-g}) can be used to name registers.
|
|
Thus, there are 255 possible registers. A register is designated in
|
|
Emacs Lisp by the character that is its name.
|
|
|
|
@defvar register-alist
|
|
This variable is an alist of elements of the form @code{(@var{name} .
|
|
@var{contents})}. Normally, there is one element for each Emacs
|
|
register that has been used.
|
|
|
|
The object @var{name} is a character (an integer) identifying the
|
|
register.
|
|
@end defvar
|
|
|
|
The @var{contents} of a register can have several possible types:
|
|
|
|
@table @asis
|
|
@item a number
|
|
A number stands for itself. If @code{insert-register} finds a number
|
|
in the register, it converts the number to decimal.
|
|
|
|
@item a marker
|
|
A marker represents a buffer position to jump to.
|
|
|
|
@item a string
|
|
A string is text saved in the register.
|
|
|
|
@item a rectangle
|
|
A rectangle is represented by a list of strings.
|
|
|
|
@item @code{(@var{window-configuration} @var{position})}
|
|
This represents a window configuration to restore in one frame, and a
|
|
position to jump to in the current buffer.
|
|
|
|
@item @code{(@var{frame-configuration} @var{position})}
|
|
This represents a frame configuration to restore, and a position
|
|
to jump to in the current buffer.
|
|
|
|
@item (file @var{filename})
|
|
This represents a file to visit; jumping to this value visits file
|
|
@var{filename}.
|
|
|
|
@item (file-query @var{filename} @var{position})
|
|
This represents a file to visit and a position in it; jumping to this
|
|
value visits file @var{filename} and goes to buffer position
|
|
@var{position}. Restoring this type of position asks the user for
|
|
confirmation first.
|
|
@end table
|
|
|
|
The functions in this section return unpredictable values unless
|
|
otherwise stated.
|
|
|
|
@defun get-register reg
|
|
This function returns the contents of the register
|
|
@var{reg}, or @code{nil} if it has no contents.
|
|
@end defun
|
|
|
|
@defun set-register reg value
|
|
This function sets the contents of register @var{reg} to @var{value}.
|
|
A register can be set to any value, but the other register functions
|
|
expect only certain data types. The return value is @var{value}.
|
|
@end defun
|
|
|
|
@deffn Command view-register reg
|
|
This command displays what is contained in register @var{reg}.
|
|
@end deffn
|
|
|
|
@ignore
|
|
@deffn Command point-to-register reg
|
|
This command stores both the current location of point and the current
|
|
buffer in register @var{reg} as a marker.
|
|
@end deffn
|
|
|
|
@deffn Command jump-to-register reg
|
|
@deffnx Command register-to-point reg
|
|
@comment !!SourceFile register.el
|
|
This command restores the status recorded in register @var{reg}.
|
|
|
|
If @var{reg} contains a marker, it moves point to the position stored in
|
|
the marker. Since both the buffer and the location within the buffer
|
|
are stored by the @code{point-to-register} function, this command can
|
|
switch you to another buffer.
|
|
|
|
If @var{reg} contains a window configuration or a frame configuration.
|
|
@code{jump-to-register} restores that configuration.
|
|
@end deffn
|
|
@end ignore
|
|
|
|
@deffn Command insert-register reg &optional beforep
|
|
This command inserts contents of register @var{reg} into the current
|
|
buffer.
|
|
|
|
Normally, this command puts point before the inserted text, and the
|
|
mark after it. However, if the optional second argument @var{beforep}
|
|
is non-@code{nil}, it puts the mark before and point after.
|
|
You can pass a non-@code{nil} second argument @var{beforep} to this
|
|
function interactively by supplying any prefix argument.
|
|
|
|
If the register contains a rectangle, then the rectangle is inserted
|
|
with its upper left corner at point. This means that text is inserted
|
|
in the current line and underneath it on successive lines.
|
|
|
|
If the register contains something other than saved text (a string) or
|
|
a rectangle (a list), currently useless things happen. This may be
|
|
changed in the future.
|
|
@end deffn
|
|
|
|
@ignore
|
|
@deffn Command copy-to-register reg start end &optional delete-flag
|
|
This command copies the region from @var{start} to @var{end} into
|
|
register @var{reg}. If @var{delete-flag} is non-@code{nil}, it deletes
|
|
the region from the buffer after copying it into the register.
|
|
@end deffn
|
|
|
|
@deffn Command prepend-to-register reg start end &optional delete-flag
|
|
This command prepends the region from @var{start} to @var{end} into
|
|
register @var{reg}. If @var{delete-flag} is non-@code{nil}, it deletes
|
|
the region from the buffer after copying it to the register.
|
|
@end deffn
|
|
|
|
@deffn Command append-to-register reg start end &optional delete-flag
|
|
This command appends the region from @var{start} to @var{end} to the
|
|
text already in register @var{reg}. If @var{delete-flag} is
|
|
non-@code{nil}, it deletes the region from the buffer after copying it
|
|
to the register.
|
|
@end deffn
|
|
|
|
@deffn Command copy-rectangle-to-register reg start end &optional delete-flag
|
|
This command copies a rectangular region from @var{start} to @var{end}
|
|
into register @var{reg}. If @var{delete-flag} is non-@code{nil}, it
|
|
deletes the region from the buffer after copying it to the register.
|
|
@end deffn
|
|
|
|
@deffn Command window-configuration-to-register reg
|
|
This function stores the window configuration of the selected frame in
|
|
register @var{reg}.
|
|
@end deffn
|
|
|
|
@deffn Command frame-configuration-to-register reg
|
|
This function stores the current frame configuration in register
|
|
@var{reg}.
|
|
@end deffn
|
|
@end ignore
|
|
|
|
@node Transposition
|
|
@section Transposition of Text
|
|
|
|
This subroutine is used by the transposition commands.
|
|
|
|
@defun transpose-regions start1 end1 start2 end2 &optional leave-markers
|
|
This function exchanges two nonoverlapping portions of the buffer.
|
|
Arguments @var{start1} and @var{end1} specify the bounds of one portion
|
|
and arguments @var{start2} and @var{end2} specify the bounds of the
|
|
other portion.
|
|
|
|
Normally, @code{transpose-regions} relocates markers with the transposed
|
|
text; a marker previously positioned within one of the two transposed
|
|
portions moves along with that portion, thus remaining between the same
|
|
two characters in their new position. However, if @var{leave-markers}
|
|
is non-@code{nil}, @code{transpose-regions} does not do this---it leaves
|
|
all markers unrelocated.
|
|
@end defun
|
|
|
|
@node Base 64
|
|
@section Base 64 Encoding
|
|
@cindex base 64 encoding
|
|
|
|
Base 64 code is used in email to encode a sequence of 8-bit bytes as
|
|
a longer sequence of @acronym{ASCII} graphic characters. It is defined in
|
|
Internet RFC@footnote{
|
|
An RFC, an acronym for @dfn{Request for Comments}, is a numbered
|
|
Internet informational document describing a standard. RFCs are
|
|
usually written by technical experts acting on their own initiative,
|
|
and are traditionally written in a pragmatic, experience-driven
|
|
manner.
|
|
}2045. This section describes the functions for
|
|
converting to and from this code.
|
|
|
|
@defun base64-encode-region beg end &optional no-line-break
|
|
@tindex base64-encode-region
|
|
This function converts the region from @var{beg} to @var{end} into base
|
|
64 code. It returns the length of the encoded text. An error is
|
|
signaled if a character in the region is multibyte, i.e.@: in a
|
|
multibyte buffer the region must contain only characters from the
|
|
charsets @code{ascii}, @code{eight-bit-control} and
|
|
@code{eight-bit-graphic}.
|
|
|
|
Normally, this function inserts newline characters into the encoded
|
|
text, to avoid overlong lines. However, if the optional argument
|
|
@var{no-line-break} is non-@code{nil}, these newlines are not added, so
|
|
the output is just one long line.
|
|
@end defun
|
|
|
|
@defun base64-encode-string string &optional no-line-break
|
|
@tindex base64-encode-string
|
|
This function converts the string @var{string} into base 64 code. It
|
|
returns a string containing the encoded text. As for
|
|
@code{base64-encode-region}, an error is signaled if a character in the
|
|
string is multibyte.
|
|
|
|
Normally, this function inserts newline characters into the encoded
|
|
text, to avoid overlong lines. However, if the optional argument
|
|
@var{no-line-break} is non-@code{nil}, these newlines are not added, so
|
|
the result string is just one long line.
|
|
@end defun
|
|
|
|
@defun base64-decode-region beg end
|
|
@tindex base64-decode-region
|
|
This function converts the region from @var{beg} to @var{end} from base
|
|
64 code into the corresponding decoded text. It returns the length of
|
|
the decoded text.
|
|
|
|
The decoding functions ignore newline characters in the encoded text.
|
|
@end defun
|
|
|
|
@defun base64-decode-string string
|
|
@tindex base64-decode-string
|
|
This function converts the string @var{string} from base 64 code into
|
|
the corresponding decoded text. It returns a unibyte string containing the
|
|
decoded text.
|
|
|
|
The decoding functions ignore newline characters in the encoded text.
|
|
@end defun
|
|
|
|
@node MD5 Checksum
|
|
@section MD5 Checksum
|
|
@cindex MD5 checksum
|
|
@cindex message digest computation
|
|
|
|
MD5 cryptographic checksums, or @dfn{message digests}, are 128-bit
|
|
``fingerprints'' of a document or program. They are used to verify
|
|
that you have an exact and unaltered copy of the data. The algorithm
|
|
to calculate the MD5 message digest is defined in Internet
|
|
RFC@footnote{
|
|
For an explanation of what is an RFC, see the footnote in @ref{Base
|
|
64}.
|
|
}1321. This section describes the Emacs facilities for computing
|
|
message digests.
|
|
|
|
@defun md5 object &optional start end coding-system noerror
|
|
This function returns the MD5 message digest of @var{object}, which
|
|
should be a buffer or a string.
|
|
|
|
The two optional arguments @var{start} and @var{end} are character
|
|
positions specifying the portion of @var{object} to compute the
|
|
message digest for. If they are @code{nil} or omitted, the digest is
|
|
computed for the whole of @var{object}.
|
|
|
|
The function @code{md5} does not compute the message digest directly
|
|
from the internal Emacs representation of the text (@pxref{Text
|
|
Representations}). Instead, it encodes the text using a coding
|
|
system, and computes the message digest from the encoded text. The
|
|
optional fourth argument @var{coding-system} specifies which coding
|
|
system to use for encoding the text. It should be the same coding
|
|
system that you used to read the text, or that you used or will use
|
|
when saving or sending the text. @xref{Coding Systems}, for more
|
|
information about coding systems.
|
|
|
|
If @var{coding-system} is @code{nil} or omitted, the default depends
|
|
on @var{object}. If @var{object} is a buffer, the default for
|
|
@var{coding-system} is whatever coding system would be chosen by
|
|
default for writing this text into a file. If @var{object} is a
|
|
string, the user's most preferred coding system (@pxref{Recognize
|
|
Coding, prefer-coding-system, the description of
|
|
@code{prefer-coding-system}, emacs, GNU Emacs Manual}) is used.
|
|
|
|
Normally, @code{md5} signals an error if the text can't be encoded
|
|
using the specified or chosen coding system. However, if
|
|
@var{noerror} is non-@code{nil}, it silently uses @code{raw-text}
|
|
coding instead.
|
|
@end defun
|
|
|
|
@node Atomic Changes
|
|
@section Atomic Change Groups
|
|
@cindex atomic changes
|
|
|
|
In data base terminology, an @dfn{atomic} change is an indivisible
|
|
change---it can succeed entirely or it can fail entirely, but it
|
|
cannot partly succeed. A Lisp program can make a series of changes to
|
|
one or several buffers as an @dfn{atomic change group}, meaning that
|
|
either the entire series of changes will be installed in their buffers
|
|
or, in case of an error, none of them will be.
|
|
|
|
To do this for one buffer, the one already current, simply write a
|
|
call to @code{atomic-change-group} around the code that makes the
|
|
changes, like this:
|
|
|
|
@example
|
|
(atomic-change-group
|
|
(insert foo)
|
|
(delete-region x y))
|
|
@end example
|
|
|
|
@noindent
|
|
If an error (or other nonlocal exit) occurs inside the body of
|
|
@code{atomic-change-group}, it unmakes all the changes in that buffer
|
|
that were during the execution of the body. This kind of change group
|
|
has no effect on any other buffers--any such changes remain.
|
|
|
|
If you need something more sophisticated, such as to make changes in
|
|
various buffers constitute one atomic group, you must directly call
|
|
lower-level functions that @code{atomic-change-group} uses.
|
|
|
|
@defun prepare-change-group &optional buffer
|
|
This function sets up a change group for buffer @var{buffer}, which
|
|
defaults to the current buffer. It returns a ``handle'' that
|
|
represents the change group. You must use this handle to activate the
|
|
change group and subsequently to finish it.
|
|
@end defun
|
|
|
|
To use the change group, you must @dfn{activate} it. You must do
|
|
this before making any changes in the text of @var{buffer}.
|
|
|
|
@defun activate-change-group handle
|
|
This function activates the change group that @var{handle} designates.
|
|
@end defun
|
|
|
|
After you activate the change group, any changes you make in that
|
|
buffer become part of it. Once you have made all the desired changes
|
|
in the buffer, you must @dfn{finish} the change group. There are two
|
|
ways to do this: you can either accept (and finalize) all the changes,
|
|
or cancel them all.
|
|
|
|
@defun accept-change-group handle
|
|
This function accepts all the changes in the change group specified by
|
|
@var{handle}, making them final.
|
|
@end defun
|
|
|
|
@defun cancel-change-group handle
|
|
This function cancels and undoes all the changes in the change group
|
|
specified by @var{handle}.
|
|
@end defun
|
|
|
|
Your code should use @code{unwind-protect} to make sure the group is
|
|
always finished. The call to @code{activate-change-group} should be
|
|
inside the @code{unwind-protect}, in case the user types @kbd{C-g}
|
|
just after it runs. (This is one reason why
|
|
@code{prepare-change-group} and @code{activate-change-group} are
|
|
separate functions, because normally you would call
|
|
@code{prepare-change-group} before the start of that
|
|
@code{unwind-protect}.) Once you finish the group, don't use the
|
|
handle again---in particular, don't try to finish the same group
|
|
twice.
|
|
|
|
To make a multibuffer change group, call @code{prepare-change-group}
|
|
once for each buffer you want to cover, then use @code{nconc} to
|
|
combine the returned values, like this:
|
|
|
|
@example
|
|
(nconc (prepare-change-group buffer-1)
|
|
(prepare-change-group buffer-2))
|
|
@end example
|
|
|
|
You can then activate the multibuffer change group with a single call
|
|
to @code{activate-change-group}, and finish it with a single call to
|
|
@code{accept-change-group} or @code{cancel-change-group}.
|
|
|
|
Nested use of several change groups for the same buffer works as you
|
|
would expect. Non-nested use of change groups for the same buffer
|
|
will get Emacs confused, so don't let it happen; the first change
|
|
group you start for any given buffer should be the last one finished.
|
|
|
|
@node Change Hooks
|
|
@section Change Hooks
|
|
@cindex change hooks
|
|
@cindex hooks for text changes
|
|
|
|
These hook variables let you arrange to take notice of all changes in
|
|
all buffers (or in a particular buffer, if you make them buffer-local).
|
|
See also @ref{Special Properties}, for how to detect changes to specific
|
|
parts of the text.
|
|
|
|
The functions you use in these hooks should save and restore the match
|
|
data if they do anything that uses regular expressions; otherwise, they
|
|
will interfere in bizarre ways with the editing operations that call
|
|
them.
|
|
|
|
@defvar before-change-functions
|
|
This variable holds a list of functions to call before any buffer
|
|
modification. Each function gets two arguments, the beginning and end
|
|
of the region that is about to change, represented as integers. The
|
|
buffer that is about to change is always the current buffer.
|
|
@end defvar
|
|
|
|
@defvar after-change-functions
|
|
This variable holds a list of functions to call after any buffer
|
|
modification. Each function receives three arguments: the beginning and
|
|
end of the region just changed, and the length of the text that existed
|
|
before the change. All three arguments are integers. The buffer that's
|
|
about to change is always the current buffer.
|
|
|
|
The length of the old text is the difference between the buffer positions
|
|
before and after that text as it was before the change. As for the
|
|
changed text, its length is simply the difference between the first two
|
|
arguments.
|
|
@end defvar
|
|
|
|
Output of messages into the @samp{*Messages*} buffer does not
|
|
call these functions.
|
|
|
|
@defmac combine-after-change-calls body...
|
|
The macro executes @var{body} normally, but arranges to call the
|
|
after-change functions just once for a series of several changes---if
|
|
that seems safe.
|
|
|
|
If a program makes several text changes in the same area of the buffer,
|
|
using the macro @code{combine-after-change-calls} around that part of
|
|
the program can make it run considerably faster when after-change hooks
|
|
are in use. When the after-change hooks are ultimately called, the
|
|
arguments specify a portion of the buffer including all of the changes
|
|
made within the @code{combine-after-change-calls} body.
|
|
|
|
@strong{Warning:} You must not alter the values of
|
|
@code{after-change-functions} within
|
|
the body of a @code{combine-after-change-calls} form.
|
|
|
|
@strong{Warning:} if the changes you combine occur in widely scattered
|
|
parts of the buffer, this will still work, but it is not advisable,
|
|
because it may lead to inefficient behavior for some change hook
|
|
functions.
|
|
@end defmac
|
|
|
|
The two variables above are temporarily bound to @code{nil} during the
|
|
time that any of these functions is running. This means that if one of
|
|
these functions changes the buffer, that change won't run these
|
|
functions. If you do want a hook function to make changes that run
|
|
these functions, make it bind these variables back to their usual
|
|
values.
|
|
|
|
One inconvenient result of this protective feature is that you cannot
|
|
have a function in @code{after-change-functions} or
|
|
@code{before-change-functions} which changes the value of that variable.
|
|
But that's not a real limitation. If you want those functions to change
|
|
the list of functions to run, simply add one fixed function to the hook,
|
|
and code that function to look in another variable for other functions
|
|
to call. Here is an example:
|
|
|
|
@example
|
|
(setq my-own-after-change-functions nil)
|
|
(defun indirect-after-change-function (beg end len)
|
|
(let ((list my-own-after-change-functions))
|
|
(while list
|
|
(funcall (car list) beg end len)
|
|
(setq list (cdr list)))))
|
|
|
|
@group
|
|
(add-hooks 'after-change-functions
|
|
'indirect-after-change-function)
|
|
@end group
|
|
@end example
|
|
|
|
@defvar first-change-hook
|
|
This variable is a normal hook that is run whenever a buffer is changed
|
|
that was previously in the unmodified state.
|
|
@end defvar
|
|
|
|
@defvar inhibit-modification-hooks
|
|
@tindex inhibit-modification-hooks
|
|
If this variable is non-@code{nil}, all of the change hooks are
|
|
disabled; none of them run. This affects all the hook variables
|
|
described above in this section, as well as the hooks attached to
|
|
certain special text properties (@pxref{Special Properties}) and overlay
|
|
properties (@pxref{Overlay Properties}).
|
|
|
|
This variable is available starting in Emacs 21.
|
|
@end defvar
|
|
|
|
@ignore
|
|
arch-tag: 3721e738-a1cb-4085-bc1a-6cb8d8e1d32b
|
|
@end ignore
|