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2933 lines
108 KiB
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2933 lines
108 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
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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/commands
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@node Command Loop, Keymaps, Minibuffers, Top
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@chapter Command Loop
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@cindex editor command loop
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@cindex command loop
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When you run Emacs, it enters the @dfn{editor command loop} almost
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immediately. This loop reads key sequences, executes their definitions,
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and displays the results. In this chapter, we describe how these things
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are done, and the subroutines that allow Lisp programs to do them.
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@menu
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* Command Overview:: How the command loop reads commands.
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* Defining Commands:: Specifying how a function should read arguments.
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* Interactive Call:: Calling a command, so that it will read arguments.
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* Command Loop Info:: Variables set by the command loop for you to examine.
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* Adjusting Point:: Adjustment of point after a command.
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* Input Events:: What input looks like when you read it.
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* Reading Input:: How to read input events from the keyboard or mouse.
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* Special Events:: Events processed immediately and individually.
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* Waiting:: Waiting for user input or elapsed time.
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* Quitting:: How @kbd{C-g} works. How to catch or defer quitting.
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* Prefix Command Arguments:: How the commands to set prefix args work.
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* Recursive Editing:: Entering a recursive edit,
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and why you usually shouldn't.
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* Disabling Commands:: How the command loop handles disabled commands.
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* Command History:: How the command history is set up, and how accessed.
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* Keyboard Macros:: How keyboard macros are implemented.
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@end menu
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@node Command Overview
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@section Command Loop Overview
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The first thing the command loop must do is read a key sequence, which
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is a sequence of events that translates into a command. It does this by
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calling the function @code{read-key-sequence}. Your Lisp code can also
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call this function (@pxref{Key Sequence Input}). Lisp programs can also
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do input at a lower level with @code{read-event} (@pxref{Reading One
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Event}) or discard pending input with @code{discard-input}
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(@pxref{Event Input Misc}).
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The key sequence is translated into a command through the currently
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active keymaps. @xref{Key Lookup}, for information on how this is done.
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The result should be a keyboard macro or an interactively callable
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function. If the key is @kbd{M-x}, then it reads the name of another
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command, which it then calls. This is done by the command
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@code{execute-extended-command} (@pxref{Interactive Call}).
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To execute a command requires first reading the arguments for it.
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This is done by calling @code{command-execute} (@pxref{Interactive
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Call}). For commands written in Lisp, the @code{interactive}
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specification says how to read the arguments. This may use the prefix
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argument (@pxref{Prefix Command Arguments}) or may read with prompting
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in the minibuffer (@pxref{Minibuffers}). For example, the command
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@code{find-file} has an @code{interactive} specification which says to
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read a file name using the minibuffer. The command's function body does
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not use the minibuffer; if you call this command from Lisp code as a
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function, you must supply the file name string as an ordinary Lisp
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function argument.
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If the command is a string or vector (i.e., a keyboard macro) then
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@code{execute-kbd-macro} is used to execute it. You can call this
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function yourself (@pxref{Keyboard Macros}).
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To terminate the execution of a running command, type @kbd{C-g}. This
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character causes @dfn{quitting} (@pxref{Quitting}).
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@defvar pre-command-hook
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The editor command loop runs this normal hook before each command. At
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that time, @code{this-command} contains the command that is about to
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run, and @code{last-command} describes the previous command.
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@xref{Hooks}.
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@end defvar
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@defvar post-command-hook
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The editor command loop runs this normal hook after each command
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(including commands terminated prematurely by quitting or by errors),
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and also when the command loop is first entered. At that time,
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@code{this-command} describes the command that just ran, and
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@code{last-command} describes the command before that. @xref{Hooks}.
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@end defvar
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Quitting is suppressed while running @code{pre-command-hook} and
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@code{post-command-hook}. If an error happens while executing one of
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these hooks, it terminates execution of the hook, and clears the hook
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variable to @code{nil} so as to prevent an infinite loop of errors.
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A request coming into the Emacs server (@pxref{Emacs Server,,,
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emacs, The GNU Emacs Manual}) runs these two hooks just as a keyboard
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command does.
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@node Defining Commands
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@section Defining Commands
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@cindex defining commands
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@cindex commands, defining
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@cindex functions, making them interactive
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@cindex interactive function
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A Lisp function becomes a command when its body contains, at top
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level, a form that calls the special form @code{interactive}. This
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form does nothing when actually executed, but its presence serves as a
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flag to indicate that interactive calling is permitted. Its argument
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controls the reading of arguments for an interactive call.
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@menu
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* Using Interactive:: General rules for @code{interactive}.
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* Interactive Codes:: The standard letter-codes for reading arguments
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in various ways.
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* Interactive Examples:: Examples of how to read interactive arguments.
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@end menu
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@node Using Interactive
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@subsection Using @code{interactive}
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This section describes how to write the @code{interactive} form that
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makes a Lisp function an interactively-callable command, and how to
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examine a commands's @code{interactive} form.
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@defspec interactive arg-descriptor
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@cindex argument descriptors
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This special form declares that the function in which it appears is a
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command, and that it may therefore be called interactively (via
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@kbd{M-x} or by entering a key sequence bound to it). The argument
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@var{arg-descriptor} declares how to compute the arguments to the
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command when the command is called interactively.
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A command may be called from Lisp programs like any other function, but
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then the caller supplies the arguments and @var{arg-descriptor} has no
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effect.
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The @code{interactive} form has its effect because the command loop
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(actually, its subroutine @code{call-interactively}) scans through the
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function definition looking for it, before calling the function. Once
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the function is called, all its body forms including the
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@code{interactive} form are executed, but at this time
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@code{interactive} simply returns @code{nil} without even evaluating its
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argument.
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@end defspec
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There are three possibilities for the argument @var{arg-descriptor}:
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@itemize @bullet
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@item
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It may be omitted or @code{nil}; then the command is called with no
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arguments. This leads quickly to an error if the command requires one
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or more arguments.
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@item
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It may be a Lisp expression that is not a string; then it should be a
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form that is evaluated to get a list of arguments to pass to the
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command.
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@cindex argument evaluation form
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If this expression reads keyboard input (this includes using the
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minibuffer), keep in mind that the integer value of point or the mark
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before reading input may be incorrect after reading input. This is
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because the current buffer may be receiving subprocess output;
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if subprocess output arrives while the command is waiting for input,
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it could relocate point and the mark.
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Here's an example of what @emph{not} to do:
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@smallexample
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(interactive
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(list (region-beginning) (region-end)
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(read-string "Foo: " nil 'my-history)))
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@end smallexample
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@noindent
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Here's how to avoid the problem, by examining point and the mark only
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after reading the keyboard input:
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@smallexample
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(interactive
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(let ((string (read-string "Foo: " nil 'my-history)))
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(list (region-beginning) (region-end) string)))
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@end smallexample
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@item
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@cindex argument prompt
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It may be a string; then its contents should consist of a code character
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followed by a prompt (which some code characters use and some ignore).
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The prompt ends either with the end of the string or with a newline.
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Here is a simple example:
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@smallexample
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(interactive "bFrobnicate buffer: ")
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@end smallexample
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@noindent
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The code letter @samp{b} says to read the name of an existing buffer,
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with completion. The buffer name is the sole argument passed to the
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command. The rest of the string is a prompt.
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If there is a newline character in the string, it terminates the prompt.
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If the string does not end there, then the rest of the string should
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contain another code character and prompt, specifying another argument.
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You can specify any number of arguments in this way.
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@c Emacs 19 feature
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The prompt string can use @samp{%} to include previous argument values
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(starting with the first argument) in the prompt. This is done using
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@code{format} (@pxref{Formatting Strings}). For example, here is how
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you could read the name of an existing buffer followed by a new name to
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give to that buffer:
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@smallexample
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@group
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(interactive "bBuffer to rename: \nsRename buffer %s to: ")
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@end group
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@end smallexample
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@cindex @samp{*} in @code{interactive}
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@cindex read-only buffers in interactive
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If the first character in the string is @samp{*}, then an error is
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signaled if the buffer is read-only.
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@cindex @samp{@@} in @code{interactive}
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@c Emacs 19 feature
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If the first character in the string is @samp{@@}, and if the key
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sequence used to invoke the command includes any mouse events, then
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the window associated with the first of those events is selected
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before the command is run.
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You can use @samp{*} and @samp{@@} together; the order does not matter.
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Actual reading of arguments is controlled by the rest of the prompt
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string (starting with the first character that is not @samp{*} or
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@samp{@@}).
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@end itemize
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@cindex examining the @code{interactive} form
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@defun interactive-form function
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This function returns the @code{interactive} form of @var{function}. If
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@var{function} is a command (@pxref{Interactive Call}), the value is a
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list of the form @code{(interactive @var{spec})}, where @var{spec} is
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the descriptor specification used by the command's @code{interactive}
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form to compute the function's arguments. If @var{function} is not a
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command, @code{interactive-form} returns @code{nil}.
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@end defun
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@node Interactive Codes
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@comment node-name, next, previous, up
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@subsection Code Characters for @code{interactive}
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@cindex interactive code description
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@cindex description for interactive codes
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@cindex codes, interactive, description of
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@cindex characters for interactive codes
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The code character descriptions below contain a number of key words,
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defined here as follows:
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@table @b
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@item Completion
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@cindex interactive completion
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Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name
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completion because the argument is read using @code{completing-read}
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(@pxref{Completion}). @kbd{?} displays a list of possible completions.
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@item Existing
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Require the name of an existing object. An invalid name is not
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accepted; the commands to exit the minibuffer do not exit if the current
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input is not valid.
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@item Default
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@cindex default argument string
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A default value of some sort is used if the user enters no text in the
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minibuffer. The default depends on the code character.
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@item No I/O
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This code letter computes an argument without reading any input.
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Therefore, it does not use a prompt string, and any prompt string you
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supply is ignored.
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Even though the code letter doesn't use a prompt string, you must follow
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it with a newline if it is not the last code character in the string.
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@item Prompt
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A prompt immediately follows the code character. The prompt ends either
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with the end of the string or with a newline.
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@item Special
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This code character is meaningful only at the beginning of the
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interactive string, and it does not look for a prompt or a newline.
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It is a single, isolated character.
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@end table
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@cindex reading interactive arguments
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Here are the code character descriptions for use with @code{interactive}:
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@table @samp
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@item *
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Signal an error if the current buffer is read-only. Special.
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@item @@
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Select the window mentioned in the first mouse event in the key
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sequence that invoked this command. Special.
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@item a
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A function name (i.e., a symbol satisfying @code{fboundp}). Existing,
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Completion, Prompt.
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@item b
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The name of an existing buffer. By default, uses the name of the
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current buffer (@pxref{Buffers}). Existing, Completion, Default,
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Prompt.
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@item B
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A buffer name. The buffer need not exist. By default, uses the name of
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a recently used buffer other than the current buffer. Completion,
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Default, Prompt.
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@item c
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A character. The cursor does not move into the echo area. Prompt.
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@item C
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A command name (i.e., a symbol satisfying @code{commandp}). Existing,
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Completion, Prompt.
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@item d
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@cindex position argument
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The position of point, as an integer (@pxref{Point}). No I/O.
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@item D
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A directory name. The default is the current default directory of the
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current buffer, @code{default-directory} (@pxref{File Name Expansion}).
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Existing, Completion, Default, Prompt.
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@item e
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The first or next mouse event in the key sequence that invoked the command.
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More precisely, @samp{e} gets events that are lists, so you can look at
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the data in the lists. @xref{Input Events}. No I/O.
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You can use @samp{e} more than once in a single command's interactive
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specification. If the key sequence that invoked the command has
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@var{n} events that are lists, the @var{n}th @samp{e} provides the
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@var{n}th such event. Events that are not lists, such as function keys
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and @acronym{ASCII} characters, do not count where @samp{e} is concerned.
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@item f
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A file name of an existing file (@pxref{File Names}). The default
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directory is @code{default-directory}. Existing, Completion, Default,
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Prompt.
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@item F
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A file name. The file need not exist. Completion, Default, Prompt.
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@item i
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An irrelevant argument. This code always supplies @code{nil} as
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the argument's value. No I/O.
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@item k
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A key sequence (@pxref{Keymap Terminology}). This keeps reading events
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until a command (or undefined command) is found in the current key
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maps. The key sequence argument is represented as a string or vector.
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The cursor does not move into the echo area. Prompt.
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This kind of input is used by commands such as @code{describe-key} and
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@code{global-set-key}.
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@item K
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A key sequence, whose definition you intend to change. This works like
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@samp{k}, except that it suppresses, for the last input event in the key
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sequence, the conversions that are normally used (when necessary) to
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convert an undefined key into a defined one.
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@item m
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@cindex marker argument
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The position of the mark, as an integer. No I/O.
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@item M
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Arbitrary text, read in the minibuffer using the current buffer's input
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method, and returned as a string (@pxref{Input Methods,,, emacs, The GNU
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Emacs Manual}). Prompt.
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@item n
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A number read with the minibuffer. If the input is not a number, the
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user is asked to try again. The prefix argument, if any, is not used.
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Prompt.
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@item N
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@cindex raw prefix argument usage
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The numeric prefix argument; but if there is no prefix argument, read a
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number as with @kbd{n}. Requires a number. @xref{Prefix Command
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Arguments}. Prompt.
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@item p
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@cindex numeric prefix argument usage
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The numeric prefix argument. (Note that this @samp{p} is lower case.)
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No I/O.
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@item P
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The raw prefix argument. (Note that this @samp{P} is upper case.) No
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I/O.
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@item r
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@cindex region argument
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Point and the mark, as two numeric arguments, smallest first. This is
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the only code letter that specifies two successive arguments rather than
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one. No I/O.
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@item s
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Arbitrary text, read in the minibuffer and returned as a string
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(@pxref{Text from Minibuffer}). Terminate the input with either
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@kbd{C-j} or @key{RET}. (@kbd{C-q} may be used to include either of
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these characters in the input.) Prompt.
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@item S
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An interned symbol whose name is read in the minibuffer. Any whitespace
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character terminates the input. (Use @kbd{C-q} to include whitespace in
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the string.) Other characters that normally terminate a symbol (e.g.,
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parentheses and brackets) do not do so here. Prompt.
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@item v
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A variable declared to be a user option (i.e., satisfying the predicate
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@code{user-variable-p}). @xref{High-Level Completion}. Existing,
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Completion, Prompt.
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@item x
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A Lisp object, specified with its read syntax, terminated with a
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@kbd{C-j} or @key{RET}. The object is not evaluated. @xref{Object from
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Minibuffer}. Prompt.
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@item X
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@cindex evaluated expression argument
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A Lisp form is read as with @kbd{x}, but then evaluated so that its
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value becomes the argument for the command. Prompt.
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@item z
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A coding system name (a symbol). If the user enters null input, the
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argument value is @code{nil}. @xref{Coding Systems}. Completion,
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Existing, Prompt.
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@item Z
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A coding system name (a symbol)---but only if this command has a prefix
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argument. With no prefix argument, @samp{Z} provides @code{nil} as the
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argument value. Completion, Existing, Prompt.
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@end table
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@node Interactive Examples
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@comment node-name, next, previous, up
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@subsection Examples of Using @code{interactive}
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@cindex examples of using @code{interactive}
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@cindex @code{interactive}, examples of using
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Here are some examples of @code{interactive}:
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@example
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@group
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(defun foo1 () ; @r{@code{foo1} takes no arguments,}
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(interactive) ; @r{just moves forward two words.}
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(forward-word 2))
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@result{} foo1
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@end group
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@group
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(defun foo2 (n) ; @r{@code{foo2} takes one argument,}
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(interactive "p") ; @r{which is the numeric prefix.}
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(forward-word (* 2 n)))
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@result{} foo2
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@end group
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@group
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(defun foo3 (n) ; @r{@code{foo3} takes one argument,}
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(interactive "nCount:") ; @r{which is read with the Minibuffer.}
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(forward-word (* 2 n)))
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@result{} foo3
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@end group
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@group
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(defun three-b (b1 b2 b3)
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"Select three existing buffers.
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Put them into three windows, selecting the last one."
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@end group
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(interactive "bBuffer1:\nbBuffer2:\nbBuffer3:")
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(delete-other-windows)
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(split-window (selected-window) 8)
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(switch-to-buffer b1)
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(other-window 1)
|
|
(split-window (selected-window) 8)
|
|
(switch-to-buffer b2)
|
|
(other-window 1)
|
|
(switch-to-buffer b3))
|
|
@result{} three-b
|
|
@group
|
|
(three-b "*scratch*" "declarations.texi" "*mail*")
|
|
@result{} nil
|
|
@end group
|
|
@end example
|
|
|
|
@node Interactive Call
|
|
@section Interactive Call
|
|
@cindex interactive call
|
|
|
|
After the command loop has translated a key sequence into a command it
|
|
invokes that command using the function @code{command-execute}. If the
|
|
command is a function, @code{command-execute} calls
|
|
@code{call-interactively}, which reads the arguments and calls the
|
|
command. You can also call these functions yourself.
|
|
|
|
@defun commandp object &optional for-call-interactively
|
|
Returns @code{t} if @var{object} is suitable for calling interactively;
|
|
that is, if @var{object} is a command. Otherwise, returns @code{nil}.
|
|
|
|
The interactively callable objects include strings and vectors (treated
|
|
as keyboard macros), lambda expressions that contain a top-level call to
|
|
@code{interactive}, byte-code function objects made from such lambda
|
|
expressions, autoload objects that are declared as interactive
|
|
(non-@code{nil} fourth argument to @code{autoload}), and some of the
|
|
primitive functions.
|
|
|
|
A symbol satisfies @code{commandp} if its function definition
|
|
satisfies @code{commandp}. Keys and keymaps are not commands.
|
|
Rather, they are used to look up commands (@pxref{Keymaps}).
|
|
|
|
If @var{for-call-interactively} is non-@code{nil}, then
|
|
@code{commandp} returns @code{t} only for objects that
|
|
@code{call-interactively} could call---thus, not for keyboard macros.
|
|
|
|
See @code{documentation} in @ref{Accessing Documentation}, for a
|
|
realistic example of using @code{commandp}.
|
|
@end defun
|
|
|
|
@defun call-interactively command &optional record-flag keys
|
|
This function calls the interactively callable function @var{command},
|
|
reading arguments according to its interactive calling specifications.
|
|
An error is signaled if @var{command} is not a function or if it cannot
|
|
be called interactively (i.e., is not a command). Note that keyboard
|
|
macros (strings and vectors) are not accepted, even though they are
|
|
considered commands, because they are not functions.
|
|
|
|
@cindex record command history
|
|
If @var{record-flag} is non-@code{nil}, then this command and its
|
|
arguments are unconditionally added to the list @code{command-history}.
|
|
Otherwise, the command is added only if it uses the minibuffer to read
|
|
an argument. @xref{Command History}.
|
|
|
|
The argument @var{keys}, if given, specifies the sequence of events to
|
|
supply if the command inquires which events were used to invoke it.
|
|
@end defun
|
|
|
|
@defun command-execute command &optional record-flag keys special
|
|
@cindex keyboard macro execution
|
|
This function executes @var{command}. The argument @var{command} must
|
|
satisfy the @code{commandp} predicate; i.e., it must be an interactively
|
|
callable function or a keyboard macro.
|
|
|
|
A string or vector as @var{command} is executed with
|
|
@code{execute-kbd-macro}. A function is passed to
|
|
@code{call-interactively}, along with the optional @var{record-flag}.
|
|
|
|
A symbol is handled by using its function definition in its place. A
|
|
symbol with an @code{autoload} definition counts as a command if it was
|
|
declared to stand for an interactively callable function. Such a
|
|
definition is handled by loading the specified library and then
|
|
rechecking the definition of the symbol.
|
|
|
|
The argument @var{keys}, if given, specifies the sequence of events to
|
|
supply if the command inquires which events were used to invoke it.
|
|
|
|
The argument @var{special}, if given, means to ignore the prefix
|
|
argument and not clear it. This is used for executing special events
|
|
(@pxref{Special Events}).
|
|
@end defun
|
|
|
|
@deffn Command execute-extended-command prefix-argument
|
|
@cindex read command name
|
|
This function reads a command name from the minibuffer using
|
|
@code{completing-read} (@pxref{Completion}). Then it uses
|
|
@code{command-execute} to call the specified command. Whatever that
|
|
command returns becomes the value of @code{execute-extended-command}.
|
|
|
|
@cindex execute with prefix argument
|
|
If the command asks for a prefix argument, it receives the value
|
|
@var{prefix-argument}. If @code{execute-extended-command} is called
|
|
interactively, the current raw prefix argument is used for
|
|
@var{prefix-argument}, and thus passed on to whatever command is run.
|
|
|
|
@c !!! Should this be @kindex?
|
|
@cindex @kbd{M-x}
|
|
@code{execute-extended-command} is the normal definition of @kbd{M-x},
|
|
so it uses the string @w{@samp{M-x }} as a prompt. (It would be better
|
|
to take the prompt from the events used to invoke
|
|
@code{execute-extended-command}, but that is painful to implement.) A
|
|
description of the value of the prefix argument, if any, also becomes
|
|
part of the prompt.
|
|
|
|
@example
|
|
@group
|
|
(execute-extended-command 1)
|
|
---------- Buffer: Minibuffer ----------
|
|
1 M-x forward-word RET
|
|
---------- Buffer: Minibuffer ----------
|
|
@result{} t
|
|
@end group
|
|
@end example
|
|
@end deffn
|
|
|
|
@defun interactive-p
|
|
This function returns @code{t} if the containing function (the one whose
|
|
code includes the call to @code{interactive-p}) was called
|
|
interactively, with the function @code{call-interactively}. (It makes
|
|
no difference whether @code{call-interactively} was called from Lisp or
|
|
directly from the editor command loop.) If the containing function was
|
|
called by Lisp evaluation (or with @code{apply} or @code{funcall}), then
|
|
it was not called interactively.
|
|
@end defun
|
|
|
|
The most common use of @code{interactive-p} is for deciding whether to
|
|
print an informative message. As a special exception,
|
|
@code{interactive-p} returns @code{nil} whenever a keyboard macro is
|
|
being run. This is to suppress the informative messages and speed
|
|
execution of the macro.
|
|
|
|
For example:
|
|
|
|
@example
|
|
@group
|
|
(defun foo ()
|
|
(interactive)
|
|
(when (interactive-p)
|
|
(message "foo")))
|
|
@result{} foo
|
|
@end group
|
|
|
|
@group
|
|
(defun bar ()
|
|
(interactive)
|
|
(setq foobar (list (foo) (interactive-p))))
|
|
@result{} bar
|
|
@end group
|
|
|
|
@group
|
|
;; @r{Type @kbd{M-x foo}.}
|
|
@print{} foo
|
|
@end group
|
|
|
|
@group
|
|
;; @r{Type @kbd{M-x bar}.}
|
|
;; @r{This does not print anything.}
|
|
@end group
|
|
|
|
@group
|
|
foobar
|
|
@result{} (nil t)
|
|
@end group
|
|
@end example
|
|
|
|
The other way to do this sort of job is to make the command take an
|
|
argument @code{print-message} which should be non-@code{nil} in an
|
|
interactive call, and use the @code{interactive} spec to make sure it is
|
|
non-@code{nil}. Here's how:
|
|
|
|
@example
|
|
(defun foo (&optional print-message)
|
|
(interactive "p")
|
|
(when print-message
|
|
(message "foo")))
|
|
@end example
|
|
|
|
@noindent
|
|
Defined in this way, the function does display the message when
|
|
called from a keyboard macro.
|
|
|
|
The numeric prefix argument, provided by @samp{p}, is never @code{nil}.
|
|
|
|
@node Command Loop Info
|
|
@comment node-name, next, previous, up
|
|
@section Information from the Command Loop
|
|
|
|
The editor command loop sets several Lisp variables to keep status
|
|
records for itself and for commands that are run.
|
|
|
|
@defvar last-command
|
|
This variable records the name of the previous command executed by the
|
|
command loop (the one before the current command). Normally the value
|
|
is a symbol with a function definition, but this is not guaranteed.
|
|
|
|
The value is copied from @code{this-command} when a command returns to
|
|
the command loop, except when the command has specified a prefix
|
|
argument for the following command.
|
|
|
|
This variable is always local to the current terminal and cannot be
|
|
buffer-local. @xref{Multiple Displays}.
|
|
@end defvar
|
|
|
|
@defvar real-last-command
|
|
This variable is set up by Emacs just like @code{last-command},
|
|
but never altered by Lisp programs.
|
|
@end defvar
|
|
|
|
@defvar this-command
|
|
@cindex current command
|
|
This variable records the name of the command now being executed by
|
|
the editor command loop. Like @code{last-command}, it is normally a symbol
|
|
with a function definition.
|
|
|
|
The command loop sets this variable just before running a command, and
|
|
copies its value into @code{last-command} when the command finishes
|
|
(unless the command specified a prefix argument for the following
|
|
command).
|
|
|
|
@cindex kill command repetition
|
|
Some commands set this variable during their execution, as a flag for
|
|
whatever command runs next. In particular, the functions for killing text
|
|
set @code{this-command} to @code{kill-region} so that any kill commands
|
|
immediately following will know to append the killed text to the
|
|
previous kill.
|
|
@end defvar
|
|
|
|
If you do not want a particular command to be recognized as the previous
|
|
command in the case where it got an error, you must code that command to
|
|
prevent this. One way is to set @code{this-command} to @code{t} at the
|
|
beginning of the command, and set @code{this-command} back to its proper
|
|
value at the end, like this:
|
|
|
|
@example
|
|
(defun foo (args@dots{})
|
|
(interactive @dots{})
|
|
(let ((old-this-command this-command))
|
|
(setq this-command t)
|
|
@r{@dots{}do the work@dots{}}
|
|
(setq this-command old-this-command)))
|
|
@end example
|
|
|
|
@noindent
|
|
We do not bind @code{this-command} with @code{let} because that would
|
|
restore the old value in case of error---a feature of @code{let} which
|
|
in this case does precisely what we want to avoid.
|
|
|
|
@defvar this-original-command
|
|
This has the same value as @code{this-command} except when command
|
|
remapping occurs (@pxref{Remapping Commands}). In that case,
|
|
@code{this-command} gives the command actually run (the result of
|
|
remapping), and @code{this-original-command} gives the command that
|
|
was specified to run but remapped into another command.
|
|
@end defvar
|
|
|
|
@defun this-command-keys
|
|
This function returns a string or vector containing the key sequence
|
|
that invoked the present command, plus any previous commands that
|
|
generated the prefix argument for this command. The value is a string
|
|
if all those events were characters. @xref{Input Events}.
|
|
|
|
@example
|
|
@group
|
|
(this-command-keys)
|
|
;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.}
|
|
@result{} "^U^X^E"
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun this-command-keys-vector
|
|
Like @code{this-command-keys}, except that it always returns the events
|
|
in a vector, so you don't need to deal with the complexities of storing
|
|
input events in a string (@pxref{Strings of Events}).
|
|
@end defun
|
|
|
|
@tindex clear-this-command-keys
|
|
@defun clear-this-command-keys
|
|
This function empties out the table of events for
|
|
@code{this-command-keys} to return, and also empties the records that
|
|
the function @code{recent-keys} (@pxref{Recording Input}) will
|
|
subsequently return. This is useful after reading a password, to
|
|
prevent the password from echoing inadvertently as part of the next
|
|
command in certain cases.
|
|
@end defun
|
|
|
|
@defvar last-nonmenu-event
|
|
This variable holds the last input event read as part of a key sequence,
|
|
not counting events resulting from mouse menus.
|
|
|
|
One use of this variable is for telling @code{x-popup-menu} where to pop
|
|
up a menu. It is also used internally by @code{y-or-n-p}
|
|
(@pxref{Yes-or-No Queries}).
|
|
@end defvar
|
|
|
|
@defvar last-command-event
|
|
@defvarx last-command-char
|
|
This variable is set to the last input event that was read by the
|
|
command loop as part of a command. The principal use of this variable
|
|
is in @code{self-insert-command}, which uses it to decide which
|
|
character to insert.
|
|
|
|
@example
|
|
@group
|
|
last-command-event
|
|
;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.}
|
|
@result{} 5
|
|
@end group
|
|
@end example
|
|
|
|
@noindent
|
|
The value is 5 because that is the @acronym{ASCII} code for @kbd{C-e}.
|
|
|
|
The alias @code{last-command-char} exists for compatibility with
|
|
Emacs version 18.
|
|
@end defvar
|
|
|
|
@c Emacs 19 feature
|
|
@defvar last-event-frame
|
|
This variable records which frame the last input event was directed to.
|
|
Usually this is the frame that was selected when the event was
|
|
generated, but if that frame has redirected input focus to another
|
|
frame, the value is the frame to which the event was redirected.
|
|
@xref{Input Focus}.
|
|
@end defvar
|
|
|
|
@node Adjusting Point
|
|
@section Adjusting Point After Commands
|
|
|
|
It is not easy to display a value of point in the middle of a sequence
|
|
of text that has the @code{display} or @code{composition} property. So
|
|
after a command finishes and returns to the command loop, if point is
|
|
within such a sequence, the command loop normally moves point to the
|
|
edge of the sequence.
|
|
|
|
A command can inhibit this feature by setting the variable
|
|
@code{disable-point-adjustment}:
|
|
|
|
@defvar disable-point-adjustment
|
|
@tindex disable-point-adjustment
|
|
If this variable is non-@code{nil} when a command returns to the command
|
|
loop, then the command loop does not check for text properties such as
|
|
@code{display} and @code{composition}, and does not move point out of
|
|
sequences that have these properties.
|
|
|
|
The command loop sets this variable to @code{nil} before each command,
|
|
so if a command sets it, the effect applies only to that command.
|
|
@end defvar
|
|
|
|
@defvar global-disable-point-adjustment
|
|
@tindex global-disable-point-adjustment
|
|
If you set this variable to a non-@code{nil} value, the feature of
|
|
moving point out of these sequences is completely turned off.
|
|
@end defvar
|
|
|
|
@node Input Events
|
|
@section Input Events
|
|
@cindex events
|
|
@cindex input events
|
|
|
|
The Emacs command loop reads a sequence of @dfn{input events} that
|
|
represent keyboard or mouse activity. The events for keyboard activity
|
|
are characters or symbols; mouse events are always lists. This section
|
|
describes the representation and meaning of input events in detail.
|
|
|
|
@defun eventp object
|
|
This function returns non-@code{nil} if @var{object} is an input event
|
|
or event type.
|
|
|
|
Note that any symbol might be used as an event or an event type.
|
|
@code{eventp} cannot distinguish whether a symbol is intended by Lisp
|
|
code to be used as an event. Instead, it distinguishes whether the
|
|
symbol has actually been used in an event that has been read as input in
|
|
the current Emacs session. If a symbol has not yet been so used,
|
|
@code{eventp} returns @code{nil}.
|
|
@end defun
|
|
|
|
@menu
|
|
* Keyboard Events:: Ordinary characters--keys with symbols on them.
|
|
* Function Keys:: Function keys--keys with names, not symbols.
|
|
* Mouse Events:: Overview of mouse events.
|
|
* Click Events:: Pushing and releasing a mouse button.
|
|
* Drag Events:: Moving the mouse before releasing the button.
|
|
* Button-Down Events:: A button was pushed and not yet released.
|
|
* Repeat Events:: Double and triple click (or drag, or down).
|
|
* Motion Events:: Just moving the mouse, not pushing a button.
|
|
* Focus Events:: Moving the mouse between frames.
|
|
* Misc Events:: Other events window systems can generate.
|
|
* Event Examples:: Examples of the lists for mouse events.
|
|
* Classifying Events:: Finding the modifier keys in an event symbol.
|
|
Event types.
|
|
* Accessing Events:: Functions to extract info from events.
|
|
* Strings of Events:: Special considerations for putting
|
|
keyboard character events in a string.
|
|
@end menu
|
|
|
|
@node Keyboard Events
|
|
@subsection Keyboard Events
|
|
|
|
There are two kinds of input you can get from the keyboard: ordinary
|
|
keys, and function keys. Ordinary keys correspond to characters; the
|
|
events they generate are represented in Lisp as characters. The event
|
|
type of a character event is the character itself (an integer); see
|
|
@ref{Classifying Events}.
|
|
|
|
@cindex modifier bits (of input character)
|
|
@cindex basic code (of input character)
|
|
An input character event consists of a @dfn{basic code} between 0 and
|
|
524287, plus any or all of these @dfn{modifier bits}:
|
|
|
|
@table @asis
|
|
@item meta
|
|
The
|
|
@tex
|
|
@math{2^{27}}
|
|
@end tex
|
|
@ifnottex
|
|
2**27
|
|
@end ifnottex
|
|
bit in the character code indicates a character
|
|
typed with the meta key held down.
|
|
|
|
@item control
|
|
The
|
|
@tex
|
|
@math{2^{26}}
|
|
@end tex
|
|
@ifnottex
|
|
2**26
|
|
@end ifnottex
|
|
bit in the character code indicates a non-@acronym{ASCII}
|
|
control character.
|
|
|
|
@sc{ascii} control characters such as @kbd{C-a} have special basic
|
|
codes of their own, so Emacs needs no special bit to indicate them.
|
|
Thus, the code for @kbd{C-a} is just 1.
|
|
|
|
But if you type a control combination not in @acronym{ASCII}, such as
|
|
@kbd{%} with the control key, the numeric value you get is the code
|
|
for @kbd{%} plus
|
|
@tex
|
|
@math{2^{26}}
|
|
@end tex
|
|
@ifnottex
|
|
2**26
|
|
@end ifnottex
|
|
(assuming the terminal supports non-@acronym{ASCII}
|
|
control characters).
|
|
|
|
@item shift
|
|
The
|
|
@tex
|
|
@math{2^{25}}
|
|
@end tex
|
|
@ifnottex
|
|
2**25
|
|
@end ifnottex
|
|
bit in the character code indicates an @acronym{ASCII} control
|
|
character typed with the shift key held down.
|
|
|
|
For letters, the basic code itself indicates upper versus lower case;
|
|
for digits and punctuation, the shift key selects an entirely different
|
|
character with a different basic code. In order to keep within the
|
|
@acronym{ASCII} character set whenever possible, Emacs avoids using the
|
|
@tex
|
|
@math{2^{25}}
|
|
@end tex
|
|
@ifnottex
|
|
2**25
|
|
@end ifnottex
|
|
bit for those characters.
|
|
|
|
However, @acronym{ASCII} provides no way to distinguish @kbd{C-A} from
|
|
@kbd{C-a}, so Emacs uses the
|
|
@tex
|
|
@math{2^{25}}
|
|
@end tex
|
|
@ifnottex
|
|
2**25
|
|
@end ifnottex
|
|
bit in @kbd{C-A} and not in
|
|
@kbd{C-a}.
|
|
|
|
@item hyper
|
|
The
|
|
@tex
|
|
@math{2^{24}}
|
|
@end tex
|
|
@ifnottex
|
|
2**24
|
|
@end ifnottex
|
|
bit in the character code indicates a character
|
|
typed with the hyper key held down.
|
|
|
|
@item super
|
|
The
|
|
@tex
|
|
@math{2^{23}}
|
|
@end tex
|
|
@ifnottex
|
|
2**23
|
|
@end ifnottex
|
|
bit in the character code indicates a character
|
|
typed with the super key held down.
|
|
|
|
@item alt
|
|
The
|
|
@tex
|
|
@math{2^{22}}
|
|
@end tex
|
|
@ifnottex
|
|
2**22
|
|
@end ifnottex
|
|
bit in the character code indicates a character typed with
|
|
the alt key held down. (On some terminals, the key labeled @key{ALT}
|
|
is actually the meta key.)
|
|
@end table
|
|
|
|
It is best to avoid mentioning specific bit numbers in your program.
|
|
To test the modifier bits of a character, use the function
|
|
@code{event-modifiers} (@pxref{Classifying Events}). When making key
|
|
bindings, you can use the read syntax for characters with modifier bits
|
|
(@samp{\C-}, @samp{\M-}, and so on). For making key bindings with
|
|
@code{define-key}, you can use lists such as @code{(control hyper ?x)} to
|
|
specify the characters (@pxref{Changing Key Bindings}). The function
|
|
@code{event-convert-list} converts such a list into an event type
|
|
(@pxref{Classifying Events}).
|
|
|
|
@node Function Keys
|
|
@subsection Function Keys
|
|
|
|
@cindex function keys
|
|
Most keyboards also have @dfn{function keys}---keys that have names or
|
|
symbols that are not characters. Function keys are represented in Emacs
|
|
Lisp as symbols; the symbol's name is the function key's label, in lower
|
|
case. For example, pressing a key labeled @key{F1} places the symbol
|
|
@code{f1} in the input stream.
|
|
|
|
The event type of a function key event is the event symbol itself.
|
|
@xref{Classifying Events}.
|
|
|
|
Here are a few special cases in the symbol-naming convention for
|
|
function keys:
|
|
|
|
@table @asis
|
|
@item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete}
|
|
These keys correspond to common @acronym{ASCII} control characters that have
|
|
special keys on most keyboards.
|
|
|
|
In @acronym{ASCII}, @kbd{C-i} and @key{TAB} are the same character. If the
|
|
terminal can distinguish between them, Emacs conveys the distinction to
|
|
Lisp programs by representing the former as the integer 9, and the
|
|
latter as the symbol @code{tab}.
|
|
|
|
Most of the time, it's not useful to distinguish the two. So normally
|
|
@code{function-key-map} (@pxref{Translating Input}) is set up to map
|
|
@code{tab} into 9. Thus, a key binding for character code 9 (the
|
|
character @kbd{C-i}) also applies to @code{tab}. Likewise for the other
|
|
symbols in this group. The function @code{read-char} likewise converts
|
|
these events into characters.
|
|
|
|
In @acronym{ASCII}, @key{BS} is really @kbd{C-h}. But @code{backspace}
|
|
converts into the character code 127 (@key{DEL}), not into code 8
|
|
(@key{BS}). This is what most users prefer.
|
|
|
|
@item @code{left}, @code{up}, @code{right}, @code{down}
|
|
Cursor arrow keys
|
|
@item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{}
|
|
Keypad keys (to the right of the regular keyboard).
|
|
@item @code{kp-0}, @code{kp-1}, @dots{}
|
|
Keypad keys with digits.
|
|
@item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4}
|
|
Keypad PF keys.
|
|
@item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down}
|
|
Keypad arrow keys. Emacs normally translates these into the
|
|
corresponding non-keypad keys @code{home}, @code{left}, @dots{}
|
|
@item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete}
|
|
Additional keypad duplicates of keys ordinarily found elsewhere. Emacs
|
|
normally translates these into the like-named non-keypad keys.
|
|
@end table
|
|
|
|
You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER},
|
|
@key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to
|
|
represent them is with prefixes in the symbol name:
|
|
|
|
@table @samp
|
|
@item A-
|
|
The alt modifier.
|
|
@item C-
|
|
The control modifier.
|
|
@item H-
|
|
The hyper modifier.
|
|
@item M-
|
|
The meta modifier.
|
|
@item S-
|
|
The shift modifier.
|
|
@item s-
|
|
The super modifier.
|
|
@end table
|
|
|
|
Thus, the symbol for the key @key{F3} with @key{META} held down is
|
|
@code{M-f3}. When you use more than one prefix, we recommend you
|
|
write them in alphabetical order; but the order does not matter in
|
|
arguments to the key-binding lookup and modification functions.
|
|
|
|
@node Mouse Events
|
|
@subsection Mouse Events
|
|
|
|
Emacs supports four kinds of mouse events: click events, drag events,
|
|
button-down events, and motion events. All mouse events are represented
|
|
as lists. The @sc{car} of the list is the event type; this says which
|
|
mouse button was involved, and which modifier keys were used with it.
|
|
The event type can also distinguish double or triple button presses
|
|
(@pxref{Repeat Events}). The rest of the list elements give position
|
|
and time information.
|
|
|
|
For key lookup, only the event type matters: two events of the same type
|
|
necessarily run the same command. The command can access the full
|
|
values of these events using the @samp{e} interactive code.
|
|
@xref{Interactive Codes}.
|
|
|
|
A key sequence that starts with a mouse event is read using the keymaps
|
|
of the buffer in the window that the mouse was in, not the current
|
|
buffer. This does not imply that clicking in a window selects that
|
|
window or its buffer---that is entirely under the control of the command
|
|
binding of the key sequence.
|
|
|
|
@node Click Events
|
|
@subsection Click Events
|
|
@cindex click event
|
|
@cindex mouse click event
|
|
|
|
When the user presses a mouse button and releases it at the same
|
|
location, that generates a @dfn{click} event. All mouse click event
|
|
share the same format:
|
|
|
|
@example
|
|
(@var{event-type} @var{position} @var{click-count})
|
|
@end example
|
|
|
|
@table @asis
|
|
@item @var{event-type}
|
|
This is a symbol that indicates which mouse button was used. It is
|
|
one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the
|
|
buttons are numbered left to right.
|
|
|
|
You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-},
|
|
@samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift
|
|
and super, just as you would with function keys.
|
|
|
|
This symbol also serves as the event type of the event. Key bindings
|
|
describe events by their types; thus, if there is a key binding for
|
|
@code{mouse-1}, that binding would apply to all events whose
|
|
@var{event-type} is @code{mouse-1}.
|
|
|
|
@item @var{position}
|
|
This is the position where the mouse click occurred. The actual
|
|
format of @var{position} depends on what part of a window was clicked
|
|
on. The various formats are described below.
|
|
|
|
@item @var{click-count}
|
|
This is the number of rapid repeated presses so far of the same mouse
|
|
button. @xref{Repeat Events}.
|
|
@end table
|
|
|
|
For mouse click events in the text area, mode line, header line, or in
|
|
the marginal areas, @var{position} has this form:
|
|
|
|
@example
|
|
(@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp}
|
|
@var{object} @var{text-pos} (@var{col} . @var{row})
|
|
@var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height}))
|
|
@end example
|
|
|
|
@table @asis
|
|
@item @var{window}
|
|
This is the window in which the click occurred.
|
|
|
|
@item @var{pos-or-area}
|
|
This is the buffer position of the character clicked on in the text
|
|
area, or if clicked outside the text area, it is the window area in
|
|
which the click occurred. It is one of the symbols @code{mode-line},
|
|
@code{header-line}, @code{vertical-line}, @code{left-margin},
|
|
@code{right-margin}, @code{left-fringe}, or @code{right-fringe}.
|
|
|
|
@item @var{x}, @var{y}
|
|
These are the pixel-denominated coordinates of the click, relative to
|
|
the top left corner of @var{window}, which is @code{(0 . 0)}.
|
|
For the mode or header line, @var{y} does not have meaningful data.
|
|
For the vertical line, @var{x} does not have meaningful data.
|
|
|
|
@item @var{timestamp}
|
|
This is the time at which the event occurred, in milliseconds.
|
|
|
|
@item @var{object}
|
|
This is the object on which the click occurred. It is either
|
|
@code{nil} if there is no string property, or it has the form
|
|
(@var{string} . @var{string-pos}) when there is a string-type text
|
|
property at the click position.
|
|
|
|
@item @var{string}
|
|
This is the string on which the click occurred, including any
|
|
properties.
|
|
|
|
@item @var{string-pos}
|
|
This is the position in the string on which the click occurred,
|
|
relevant if properties at the click need to be looked up.
|
|
|
|
@item @var{text-pos}
|
|
For clicks on a marginal area or on a fringe, this is the buffer
|
|
position of the first visible character in the corresponding line in
|
|
the window. For other events, it is the current buffer position in
|
|
the window.
|
|
|
|
@item @var{col}, @var{row}
|
|
These are the actual coordinates of the glyph under the @var{x},
|
|
@var{y} position, possibly padded with default character width
|
|
glyphs if @var{x} is beyond the last glyph on the line.
|
|
|
|
@item @var{image}
|
|
This is the image object on which the click occurred. It is either
|
|
@code{nil} if there is no image at the position clicked on, or it is
|
|
an image object as returned by @code{find-image} if click was in an image.
|
|
|
|
@item @var{dx}, @var{dy}
|
|
These are the pixel-denominated coordinates of the click, relative to
|
|
the top left corner of @var{object}, which is @code{(0 . 0)}. If
|
|
@var{object} is @code{nil}, the coordinates are relative to the top
|
|
left corner of the character glyph clicked on.
|
|
@end table
|
|
|
|
For mouse clicks on a scroll-bar, @var{position} has this form:
|
|
|
|
@example
|
|
(@var{window} @var{area} (@var{portion} . @var{whole}) @var{timestamp} @var{part})
|
|
@end example
|
|
|
|
@table @asis
|
|
@item @var{window}
|
|
This is the window whose scroll-bar was clicked on.
|
|
|
|
@item @var{area}
|
|
This is the scroll bar where the click occurred. It is one of the
|
|
symbols @code{vertical-scroll-bar} or @code{horizontal-scroll-bar}.
|
|
|
|
@item @var{portion}
|
|
This is the distance of the click from the top or left end of
|
|
the scroll bar.
|
|
|
|
@item @var{whole}
|
|
This is the length of the entire scroll bar.
|
|
|
|
@item @var{timestamp}
|
|
This is the time at which the event occurred, in milliseconds.
|
|
|
|
@item @var{part}
|
|
This is the part of the scroll-bar which was clicked on. It is one
|
|
of the symbols @code{above-handle}, @code{handle}, @code{below-handle},
|
|
@code{up}, @code{down}, @code{top}, @code{bottom}, and @code{end-scroll}.
|
|
@end table
|
|
|
|
In one special case, @var{buffer-pos} is a list containing a symbol (one
|
|
of the symbols listed above) instead of just the symbol. This happens
|
|
after the imaginary prefix keys for the event are inserted into the
|
|
input stream. @xref{Key Sequence Input}.
|
|
|
|
@node Drag Events
|
|
@subsection Drag Events
|
|
@cindex drag event
|
|
@cindex mouse drag event
|
|
|
|
With Emacs, you can have a drag event without even changing your
|
|
clothes. A @dfn{drag event} happens every time the user presses a mouse
|
|
button and then moves the mouse to a different character position before
|
|
releasing the button. Like all mouse events, drag events are
|
|
represented in Lisp as lists. The lists record both the starting mouse
|
|
position and the final position, like this:
|
|
|
|
@example
|
|
(@var{event-type}
|
|
(@var{window1} @var{buffer-pos1} (@var{x1} . @var{y1}) @var{timestamp1})
|
|
(@var{window2} @var{buffer-pos2} (@var{x2} . @var{y2}) @var{timestamp2})
|
|
@var{click-count})
|
|
@end example
|
|
|
|
For a drag event, the name of the symbol @var{event-type} contains the
|
|
prefix @samp{drag-}. For example, dragging the mouse with button 2 held
|
|
down generates a @code{drag-mouse-2} event. The second and third
|
|
elements of the event give the starting and ending position of the drag.
|
|
Aside from that, the data have the same meanings as in a click event
|
|
(@pxref{Click Events}). You can access the second element of any mouse
|
|
event in the same way, with no need to distinguish drag events from
|
|
others.
|
|
|
|
The @samp{drag-} prefix follows the modifier key prefixes such as
|
|
@samp{C-} and @samp{M-}.
|
|
|
|
If @code{read-key-sequence} receives a drag event that has no key
|
|
binding, and the corresponding click event does have a binding, it
|
|
changes the drag event into a click event at the drag's starting
|
|
position. This means that you don't have to distinguish between click
|
|
and drag events unless you want to.
|
|
|
|
@node Button-Down Events
|
|
@subsection Button-Down Events
|
|
@cindex button-down event
|
|
|
|
Click and drag events happen when the user releases a mouse button.
|
|
They cannot happen earlier, because there is no way to distinguish a
|
|
click from a drag until the button is released.
|
|
|
|
If you want to take action as soon as a button is pressed, you need to
|
|
handle @dfn{button-down} events.@footnote{Button-down is the
|
|
conservative antithesis of drag.} These occur as soon as a button is
|
|
pressed. They are represented by lists that look exactly like click
|
|
events (@pxref{Click Events}), except that the @var{event-type} symbol
|
|
name contains the prefix @samp{down-}. The @samp{down-} prefix follows
|
|
modifier key prefixes such as @samp{C-} and @samp{M-}.
|
|
|
|
The function @code{read-key-sequence} ignores any button-down events
|
|
that don't have command bindings; therefore, the Emacs command loop
|
|
ignores them too. This means that you need not worry about defining
|
|
button-down events unless you want them to do something. The usual
|
|
reason to define a button-down event is so that you can track mouse
|
|
motion (by reading motion events) until the button is released.
|
|
@xref{Motion Events}.
|
|
|
|
@node Repeat Events
|
|
@subsection Repeat Events
|
|
@cindex repeat events
|
|
@cindex double-click events
|
|
@cindex triple-click events
|
|
@cindex mouse events, repeated
|
|
|
|
If you press the same mouse button more than once in quick succession
|
|
without moving the mouse, Emacs generates special @dfn{repeat} mouse
|
|
events for the second and subsequent presses.
|
|
|
|
The most common repeat events are @dfn{double-click} events. Emacs
|
|
generates a double-click event when you click a button twice; the event
|
|
happens when you release the button (as is normal for all click
|
|
events).
|
|
|
|
The event type of a double-click event contains the prefix
|
|
@samp{double-}. Thus, a double click on the second mouse button with
|
|
@key{meta} held down comes to the Lisp program as
|
|
@code{M-double-mouse-2}. If a double-click event has no binding, the
|
|
binding of the corresponding ordinary click event is used to execute
|
|
it. Thus, you need not pay attention to the double click feature
|
|
unless you really want to.
|
|
|
|
When the user performs a double click, Emacs generates first an ordinary
|
|
click event, and then a double-click event. Therefore, you must design
|
|
the command binding of the double click event to assume that the
|
|
single-click command has already run. It must produce the desired
|
|
results of a double click, starting from the results of a single click.
|
|
|
|
This is convenient, if the meaning of a double click somehow ``builds
|
|
on'' the meaning of a single click---which is recommended user interface
|
|
design practice for double clicks.
|
|
|
|
If you click a button, then press it down again and start moving the
|
|
mouse with the button held down, then you get a @dfn{double-drag} event
|
|
when you ultimately release the button. Its event type contains
|
|
@samp{double-drag} instead of just @samp{drag}. If a double-drag event
|
|
has no binding, Emacs looks for an alternate binding as if the event
|
|
were an ordinary drag.
|
|
|
|
Before the double-click or double-drag event, Emacs generates a
|
|
@dfn{double-down} event when the user presses the button down for the
|
|
second time. Its event type contains @samp{double-down} instead of just
|
|
@samp{down}. If a double-down event has no binding, Emacs looks for an
|
|
alternate binding as if the event were an ordinary button-down event.
|
|
If it finds no binding that way either, the double-down event is
|
|
ignored.
|
|
|
|
To summarize, when you click a button and then press it again right
|
|
away, Emacs generates a down event and a click event for the first
|
|
click, a double-down event when you press the button again, and finally
|
|
either a double-click or a double-drag event.
|
|
|
|
If you click a button twice and then press it again, all in quick
|
|
succession, Emacs generates a @dfn{triple-down} event, followed by
|
|
either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of
|
|
these events contain @samp{triple} instead of @samp{double}. If any
|
|
triple event has no binding, Emacs uses the binding that it would use
|
|
for the corresponding double event.
|
|
|
|
If you click a button three or more times and then press it again, the
|
|
events for the presses beyond the third are all triple events. Emacs
|
|
does not have separate event types for quadruple, quintuple, etc.@:
|
|
events. However, you can look at the event list to find out precisely
|
|
how many times the button was pressed.
|
|
|
|
@defun event-click-count event
|
|
This function returns the number of consecutive button presses that led
|
|
up to @var{event}. If @var{event} is a double-down, double-click or
|
|
double-drag event, the value is 2. If @var{event} is a triple event,
|
|
the value is 3 or greater. If @var{event} is an ordinary mouse event
|
|
(not a repeat event), the value is 1.
|
|
@end defun
|
|
|
|
@defvar double-click-fuzz
|
|
To generate repeat events, successive mouse button presses must be at
|
|
approximately the same screen position. The value of
|
|
@code{double-click-fuzz} specifies the maximum number of pixels the
|
|
mouse may be moved between two successive clicks to make a
|
|
double-click.
|
|
@end defvar
|
|
|
|
@defvar double-click-time
|
|
To generate repeat events, the number of milliseconds between
|
|
successive button presses must be less than the value of
|
|
@code{double-click-time}. Setting @code{double-click-time} to
|
|
@code{nil} disables multi-click detection entirely. Setting it to
|
|
@code{t} removes the time limit; Emacs then detects multi-clicks by
|
|
position only.
|
|
@end defvar
|
|
|
|
@node Motion Events
|
|
@subsection Motion Events
|
|
@cindex motion event
|
|
@cindex mouse motion events
|
|
|
|
Emacs sometimes generates @dfn{mouse motion} events to describe motion
|
|
of the mouse without any button activity. Mouse motion events are
|
|
represented by lists that look like this:
|
|
|
|
@example
|
|
(mouse-movement (@var{window} @var{buffer-pos} (@var{x} . @var{y}) @var{timestamp}))
|
|
@end example
|
|
|
|
The second element of the list describes the current position of the
|
|
mouse, just as in a click event (@pxref{Click Events}).
|
|
|
|
The special form @code{track-mouse} enables generation of motion events
|
|
within its body. Outside of @code{track-mouse} forms, Emacs does not
|
|
generate events for mere motion of the mouse, and these events do not
|
|
appear. @xref{Mouse Tracking}.
|
|
|
|
@node Focus Events
|
|
@subsection Focus Events
|
|
@cindex focus event
|
|
|
|
Window systems provide general ways for the user to control which window
|
|
gets keyboard input. This choice of window is called the @dfn{focus}.
|
|
When the user does something to switch between Emacs frames, that
|
|
generates a @dfn{focus event}. The normal definition of a focus event,
|
|
in the global keymap, is to select a new frame within Emacs, as the user
|
|
would expect. @xref{Input Focus}.
|
|
|
|
Focus events are represented in Lisp as lists that look like this:
|
|
|
|
@example
|
|
(switch-frame @var{new-frame})
|
|
@end example
|
|
|
|
@noindent
|
|
where @var{new-frame} is the frame switched to.
|
|
|
|
Most X window managers are set up so that just moving the mouse into a
|
|
window is enough to set the focus there. Emacs appears to do this,
|
|
because it changes the cursor to solid in the new frame. However, there
|
|
is no need for the Lisp program to know about the focus change until
|
|
some other kind of input arrives. So Emacs generates a focus event only
|
|
when the user actually types a keyboard key or presses a mouse button in
|
|
the new frame; just moving the mouse between frames does not generate a
|
|
focus event.
|
|
|
|
A focus event in the middle of a key sequence would garble the
|
|
sequence. So Emacs never generates a focus event in the middle of a key
|
|
sequence. If the user changes focus in the middle of a key
|
|
sequence---that is, after a prefix key---then Emacs reorders the events
|
|
so that the focus event comes either before or after the multi-event key
|
|
sequence, and not within it.
|
|
|
|
@node Misc Events
|
|
@subsection Miscellaneous Window System Events
|
|
|
|
A few other event types represent occurrences within the window system.
|
|
|
|
@table @code
|
|
@cindex @code{delete-frame} event
|
|
@item (delete-frame (@var{frame}))
|
|
This kind of event indicates that the user gave the window manager
|
|
a command to delete a particular window, which happens to be an Emacs frame.
|
|
|
|
The standard definition of the @code{delete-frame} event is to delete @var{frame}.
|
|
|
|
@cindex @code{iconify-frame} event
|
|
@item (iconify-frame (@var{frame}))
|
|
This kind of event indicates that the user iconified @var{frame} using
|
|
the window manager. Its standard definition is @code{ignore}; since the
|
|
frame has already been iconified, Emacs has no work to do. The purpose
|
|
of this event type is so that you can keep track of such events if you
|
|
want to.
|
|
|
|
@cindex @code{make-frame-visible} event
|
|
@item (make-frame-visible (@var{frame}))
|
|
This kind of event indicates that the user deiconified @var{frame} using
|
|
the window manager. Its standard definition is @code{ignore}; since the
|
|
frame has already been made visible, Emacs has no work to do.
|
|
|
|
@cindex @code{mouse-wheel} event
|
|
@item (mouse-wheel @var{position} @var{delta})
|
|
This kind of event is generated by moving a wheel on a mouse (such as
|
|
the MS Intellimouse). Its effect is typically a kind of scroll or zoom.
|
|
|
|
The element @var{delta} describes the amount and direction of the wheel
|
|
rotation. Its absolute value is the number of increments by which the
|
|
wheel was rotated. A negative @var{delta} indicates that the wheel was
|
|
rotated backwards, towards the user, and a positive @var{delta}
|
|
indicates that the wheel was rotated forward, away from the user.
|
|
|
|
The element @var{position} is a list describing the position of the
|
|
event, in the same format as used in a mouse-click event.
|
|
|
|
This kind of event is generated only on some kinds of systems.
|
|
|
|
@cindex @code{drag-n-drop} event
|
|
@item (drag-n-drop @var{position} @var{files})
|
|
This kind of event is generated when a group of files is
|
|
selected in an application outside of Emacs, and then dragged and
|
|
dropped onto an Emacs frame.
|
|
|
|
The element @var{position} is a list describing the position of the
|
|
event, in the same format as used in a mouse-click event, and
|
|
@var{files} is the list of file names that were dragged and dropped.
|
|
The usual way to handle this event is by visiting these files.
|
|
|
|
This kind of event is generated, at present, only on some kinds of
|
|
systems.
|
|
@end table
|
|
|
|
If one of these events arrives in the middle of a key sequence---that
|
|
is, after a prefix key---then Emacs reorders the events so that this
|
|
event comes either before or after the multi-event key sequence, not
|
|
within it.
|
|
|
|
@node Event Examples
|
|
@subsection Event Examples
|
|
|
|
If the user presses and releases the left mouse button over the same
|
|
location, that generates a sequence of events like this:
|
|
|
|
@smallexample
|
|
(down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320))
|
|
(mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180))
|
|
@end smallexample
|
|
|
|
While holding the control key down, the user might hold down the
|
|
second mouse button, and drag the mouse from one line to the next.
|
|
That produces two events, as shown here:
|
|
|
|
@smallexample
|
|
(C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219))
|
|
(C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)
|
|
(#<window 18 on NEWS> 3510 (0 . 28) -729648))
|
|
@end smallexample
|
|
|
|
While holding down the meta and shift keys, the user might press the
|
|
second mouse button on the window's mode line, and then drag the mouse
|
|
into another window. That produces a pair of events like these:
|
|
|
|
@smallexample
|
|
(M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844))
|
|
(M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)
|
|
(#<window 20 on carlton-sanskrit.tex> 161 (33 . 3)
|
|
-453816))
|
|
@end smallexample
|
|
|
|
@node Classifying Events
|
|
@subsection Classifying Events
|
|
@cindex event type
|
|
|
|
Every event has an @dfn{event type}, which classifies the event for
|
|
key binding purposes. For a keyboard event, the event type equals the
|
|
event value; thus, the event type for a character is the character, and
|
|
the event type for a function key symbol is the symbol itself. For
|
|
events that are lists, the event type is the symbol in the @sc{car} of
|
|
the list. Thus, the event type is always a symbol or a character.
|
|
|
|
Two events of the same type are equivalent where key bindings are
|
|
concerned; thus, they always run the same command. That does not
|
|
necessarily mean they do the same things, however, as some commands look
|
|
at the whole event to decide what to do. For example, some commands use
|
|
the location of a mouse event to decide where in the buffer to act.
|
|
|
|
Sometimes broader classifications of events are useful. For example,
|
|
you might want to ask whether an event involved the @key{META} key,
|
|
regardless of which other key or mouse button was used.
|
|
|
|
The functions @code{event-modifiers} and @code{event-basic-type} are
|
|
provided to get such information conveniently.
|
|
|
|
@defun event-modifiers event
|
|
This function returns a list of the modifiers that @var{event} has. The
|
|
modifiers are symbols; they include @code{shift}, @code{control},
|
|
@code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition,
|
|
the modifiers list of a mouse event symbol always contains one of
|
|
@code{click}, @code{drag}, and @code{down}.
|
|
|
|
The argument @var{event} may be an entire event object, or just an event
|
|
type.
|
|
|
|
Here are some examples:
|
|
|
|
@example
|
|
(event-modifiers ?a)
|
|
@result{} nil
|
|
(event-modifiers ?\C-a)
|
|
@result{} (control)
|
|
(event-modifiers ?\C-%)
|
|
@result{} (control)
|
|
(event-modifiers ?\C-\S-a)
|
|
@result{} (control shift)
|
|
(event-modifiers 'f5)
|
|
@result{} nil
|
|
(event-modifiers 's-f5)
|
|
@result{} (super)
|
|
(event-modifiers 'M-S-f5)
|
|
@result{} (meta shift)
|
|
(event-modifiers 'mouse-1)
|
|
@result{} (click)
|
|
(event-modifiers 'down-mouse-1)
|
|
@result{} (down)
|
|
@end example
|
|
|
|
The modifiers list for a click event explicitly contains @code{click},
|
|
but the event symbol name itself does not contain @samp{click}.
|
|
@end defun
|
|
|
|
@defun event-basic-type event
|
|
This function returns the key or mouse button that @var{event}
|
|
describes, with all modifiers removed. For example:
|
|
|
|
@example
|
|
(event-basic-type ?a)
|
|
@result{} 97
|
|
(event-basic-type ?A)
|
|
@result{} 97
|
|
(event-basic-type ?\C-a)
|
|
@result{} 97
|
|
(event-basic-type ?\C-\S-a)
|
|
@result{} 97
|
|
(event-basic-type 'f5)
|
|
@result{} f5
|
|
(event-basic-type 's-f5)
|
|
@result{} f5
|
|
(event-basic-type 'M-S-f5)
|
|
@result{} f5
|
|
(event-basic-type 'down-mouse-1)
|
|
@result{} mouse-1
|
|
@end example
|
|
@end defun
|
|
|
|
@defun mouse-movement-p object
|
|
This function returns non-@code{nil} if @var{object} is a mouse movement
|
|
event.
|
|
@end defun
|
|
|
|
@defun event-convert-list list
|
|
This function converts a list of modifier names and a basic event type
|
|
to an event type which specifies all of them. For example,
|
|
|
|
@example
|
|
(event-convert-list '(control ?a))
|
|
@result{} 1
|
|
(event-convert-list '(control meta ?a))
|
|
@result{} -134217727
|
|
(event-convert-list '(control super f1))
|
|
@result{} C-s-f1
|
|
@end example
|
|
@end defun
|
|
|
|
@node Accessing Events
|
|
@subsection Accessing Events
|
|
@cindex mouse events, accessing the data
|
|
@cindex accessing data of mouse events
|
|
|
|
This section describes convenient functions for accessing the data in
|
|
a mouse button or motion event.
|
|
|
|
These two functions return the starting or ending position of a
|
|
mouse-button event, as a list of this form:
|
|
|
|
@example
|
|
(@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp}
|
|
@var{object} @var{text-pos} (@var{col} . @var{row})
|
|
@var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height}))
|
|
@end example
|
|
|
|
@defun event-start event
|
|
This returns the starting position of @var{event}.
|
|
|
|
If @var{event} is a click or button-down event, this returns the
|
|
location of the event. If @var{event} is a drag event, this returns the
|
|
drag's starting position.
|
|
@end defun
|
|
|
|
@defun event-end event
|
|
This returns the ending position of @var{event}.
|
|
|
|
If @var{event} is a drag event, this returns the position where the user
|
|
released the mouse button. If @var{event} is a click or button-down
|
|
event, the value is actually the starting position, which is the only
|
|
position such events have.
|
|
@end defun
|
|
|
|
@cindex mouse position list, accessing
|
|
These seven functions take a position list as described above, and
|
|
return various parts of it.
|
|
|
|
@defun posn-window position
|
|
Return the window that @var{position} is in.
|
|
@end defun
|
|
|
|
@defun posn-area position
|
|
Return the window area recorded in @var{position}. It returns @code{nil}
|
|
when the event occurred in the text area of the window; otherwise, it
|
|
is a symbol identifying the area in which the the event occurred.
|
|
@end defun
|
|
|
|
@defun posn-point position
|
|
Return the buffer position in @var{position}. When the event occurred
|
|
in the text area of the window, in a marginal area, or on a fringe,
|
|
this is an integer specifying a buffer position. Otherwise, the value
|
|
is undefined.
|
|
@end defun
|
|
|
|
@defun posn-x-y position
|
|
Return the pixel-based x and y coordinates in @var{position}, as a cons
|
|
cell @code{(@var{x} . @var{y})}.
|
|
@end defun
|
|
|
|
@defun posn-col-row position
|
|
Return the row and column (in units of frame default characters) of
|
|
@var{position}, as a cons cell @code{(@var{col} . @var{row})}. These
|
|
are computed from the @var{x} and @var{y} values actually found in
|
|
@var{position}.
|
|
@end defun
|
|
|
|
@defun posn-actual-col-row position
|
|
Return the actual row and column in @var{position}, as a cons cell
|
|
@code{(@var{col} . @var{row})}. The values are the actual row number
|
|
in the window, and the actual character number in that row. Return
|
|
@code{nil} if @var{position} does not include the actual positions; in that
|
|
case, @code{posn-col-row} can be used to get approximate values.
|
|
@end defun
|
|
|
|
@defun posn-string position
|
|
Return the string object in @var{position}, either @code{nil}, or a
|
|
cons cell @code{(@var{string} . @var{string-pos})}.
|
|
@end defun
|
|
|
|
@defun posn-image position
|
|
Return the image object in @var{position}, either @code{nil}, or an
|
|
image @code{(image ...)}.
|
|
@end defun
|
|
|
|
@defun posn-object position
|
|
Return the image or string object in @var{position}, either
|
|
@code{nil}, an image @code{(image ...)}, or a cons cell
|
|
@code{(@var{string} . @var{string-pos})}.
|
|
@end defun
|
|
|
|
@defun posn-object-x-y position
|
|
Return the pixel-based x and y coordinates relative to the upper left
|
|
corner of the object in @var{position} as a cons cell @code{(@var{dx}
|
|
. @var{dy})}. If the @var{position} is a buffer position, return the
|
|
relative position in the character at that position.
|
|
@end defun
|
|
|
|
@defun posn-object-width-height position
|
|
Return the pixel width and height of the object in @var{position} as a
|
|
cons cell @code{(@var{width} . @var{height})}. If the @var{position}
|
|
is a buffer position, return the size of the character at that position.
|
|
@end defun
|
|
|
|
@cindex mouse event, timestamp
|
|
@cindex timestamp of a mouse event
|
|
@defun posn-timestamp
|
|
Return the timestamp in @var{position}. This is the time at which the
|
|
event occurred, in milliseconds.
|
|
@end defun
|
|
|
|
These functions are useful for decoding scroll bar events.
|
|
|
|
@defun scroll-bar-event-ratio event
|
|
This function returns the fractional vertical position of a scroll bar
|
|
event within the scroll bar. The value is a cons cell
|
|
@code{(@var{portion} . @var{whole})} containing two integers whose ratio
|
|
is the fractional position.
|
|
@end defun
|
|
|
|
@defun scroll-bar-scale ratio total
|
|
This function multiplies (in effect) @var{ratio} by @var{total},
|
|
rounding the result to an integer. The argument @var{ratio} is not a
|
|
number, but rather a pair @code{(@var{num} . @var{denom})}---typically a
|
|
value returned by @code{scroll-bar-event-ratio}.
|
|
|
|
This function is handy for scaling a position on a scroll bar into a
|
|
buffer position. Here's how to do that:
|
|
|
|
@example
|
|
(+ (point-min)
|
|
(scroll-bar-scale
|
|
(posn-x-y (event-start event))
|
|
(- (point-max) (point-min))))
|
|
@end example
|
|
|
|
Recall that scroll bar events have two integers forming a ratio, in place
|
|
of a pair of x and y coordinates.
|
|
@end defun
|
|
|
|
@node Strings of Events
|
|
@subsection Putting Keyboard Events in Strings
|
|
@cindex keyboard events in strings
|
|
@cindex strings with keyboard events
|
|
|
|
In most of the places where strings are used, we conceptualize the
|
|
string as containing text characters---the same kind of characters found
|
|
in buffers or files. Occasionally Lisp programs use strings that
|
|
conceptually contain keyboard characters; for example, they may be key
|
|
sequences or keyboard macro definitions. However, storing keyboard
|
|
characters in a string is a complex matter, for reasons of historical
|
|
compatibility, and it is not always possible.
|
|
|
|
We recommend that new programs avoid dealing with these complexities
|
|
by not storing keyboard events in strings. Here is how to do that:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Use vectors instead of strings for key sequences, when you plan to use
|
|
them for anything other than as arguments to @code{lookup-key} and
|
|
@code{define-key}. For example, you can use
|
|
@code{read-key-sequence-vector} instead of @code{read-key-sequence}, and
|
|
@code{this-command-keys-vector} instead of @code{this-command-keys}.
|
|
|
|
@item
|
|
Use vectors to write key sequence constants containing meta characters,
|
|
even when passing them directly to @code{define-key}.
|
|
|
|
@item
|
|
When you have to look at the contents of a key sequence that might be a
|
|
string, use @code{listify-key-sequence} (@pxref{Event Input Misc})
|
|
first, to convert it to a list.
|
|
@end itemize
|
|
|
|
The complexities stem from the modifier bits that keyboard input
|
|
characters can include. Aside from the Meta modifier, none of these
|
|
modifier bits can be included in a string, and the Meta modifier is
|
|
allowed only in special cases.
|
|
|
|
The earliest GNU Emacs versions represented meta characters as codes
|
|
in the range of 128 to 255. At that time, the basic character codes
|
|
ranged from 0 to 127, so all keyboard character codes did fit in a
|
|
string. Many Lisp programs used @samp{\M-} in string constants to stand
|
|
for meta characters, especially in arguments to @code{define-key} and
|
|
similar functions, and key sequences and sequences of events were always
|
|
represented as strings.
|
|
|
|
When we added support for larger basic character codes beyond 127, and
|
|
additional modifier bits, we had to change the representation of meta
|
|
characters. Now the flag that represents the Meta modifier in a
|
|
character is
|
|
@tex
|
|
@math{2^{27}}
|
|
@end tex
|
|
@ifnottex
|
|
2**27
|
|
@end ifnottex
|
|
and such numbers cannot be included in a string.
|
|
|
|
To support programs with @samp{\M-} in string constants, there are
|
|
special rules for including certain meta characters in a string.
|
|
Here are the rules for interpreting a string as a sequence of input
|
|
characters:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
If the keyboard character value is in the range of 0 to 127, it can go
|
|
in the string unchanged.
|
|
|
|
@item
|
|
The meta variants of those characters, with codes in the range of
|
|
@tex
|
|
@math{2^{27}}
|
|
@end tex
|
|
@ifnottex
|
|
2**27
|
|
@end ifnottex
|
|
to
|
|
@tex
|
|
@math{2^{27} + 127},
|
|
@end tex
|
|
@ifnottex
|
|
2**27+127,
|
|
@end ifnottex
|
|
can also go in the string, but you must change their
|
|
numeric values. You must set the
|
|
@tex
|
|
@math{2^{7}}
|
|
@end tex
|
|
@ifnottex
|
|
2**7
|
|
@end ifnottex
|
|
bit instead of the
|
|
@tex
|
|
@math{2^{27}}
|
|
@end tex
|
|
@ifnottex
|
|
2**27
|
|
@end ifnottex
|
|
bit, resulting in a value between 128 and 255. Only a unibyte string
|
|
can include these codes.
|
|
|
|
@item
|
|
Non-@acronym{ASCII} characters above 256 can be included in a multibyte string.
|
|
|
|
@item
|
|
Other keyboard character events cannot fit in a string. This includes
|
|
keyboard events in the range of 128 to 255.
|
|
@end itemize
|
|
|
|
Functions such as @code{read-key-sequence} that construct strings of
|
|
keyboard input characters follow these rules: they construct vectors
|
|
instead of strings, when the events won't fit in a string.
|
|
|
|
When you use the read syntax @samp{\M-} in a string, it produces a
|
|
code in the range of 128 to 255---the same code that you get if you
|
|
modify the corresponding keyboard event to put it in the string. Thus,
|
|
meta events in strings work consistently regardless of how they get into
|
|
the strings.
|
|
|
|
However, most programs would do well to avoid these issues by
|
|
following the recommendations at the beginning of this section.
|
|
|
|
@node Reading Input
|
|
@section Reading Input
|
|
|
|
The editor command loop reads key sequences using the function
|
|
@code{read-key-sequence}, which uses @code{read-event}. These and other
|
|
functions for event input are also available for use in Lisp programs.
|
|
See also @code{momentary-string-display} in @ref{Temporary Displays},
|
|
and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input}, for
|
|
functions and variables for controlling terminal input modes and
|
|
debugging terminal input. @xref{Translating Input}, for features you
|
|
can use for translating or modifying input events while reading them.
|
|
|
|
For higher-level input facilities, see @ref{Minibuffers}.
|
|
|
|
@menu
|
|
* Key Sequence Input:: How to read one key sequence.
|
|
* Reading One Event:: How to read just one event.
|
|
* Invoking the Input Method:: How reading an event uses the input method.
|
|
* Quoted Character Input:: Asking the user to specify a character.
|
|
* Event Input Misc:: How to reread or throw away input events.
|
|
@end menu
|
|
|
|
@node Key Sequence Input
|
|
@subsection Key Sequence Input
|
|
@cindex key sequence input
|
|
|
|
The command loop reads input a key sequence at a time, by calling
|
|
@code{read-key-sequence}. Lisp programs can also call this function;
|
|
for example, @code{describe-key} uses it to read the key to describe.
|
|
|
|
@defun read-key-sequence prompt
|
|
@cindex key sequence
|
|
This function reads a key sequence and returns it as a string or
|
|
vector. It keeps reading events until it has accumulated a complete key
|
|
sequence; that is, enough to specify a non-prefix command using the
|
|
currently active keymaps.
|
|
|
|
If the events are all characters and all can fit in a string, then
|
|
@code{read-key-sequence} returns a string (@pxref{Strings of Events}).
|
|
Otherwise, it returns a vector, since a vector can hold all kinds of
|
|
events---characters, symbols, and lists. The elements of the string or
|
|
vector are the events in the key sequence.
|
|
|
|
The argument @var{prompt} is either a string to be displayed in the echo
|
|
area as a prompt, or @code{nil}, meaning not to display a prompt.
|
|
|
|
In the example below, the prompt @samp{?} is displayed in the echo area,
|
|
and the user types @kbd{C-x C-f}.
|
|
|
|
@example
|
|
(read-key-sequence "?")
|
|
|
|
@group
|
|
---------- Echo Area ----------
|
|
?@kbd{C-x C-f}
|
|
---------- Echo Area ----------
|
|
|
|
@result{} "^X^F"
|
|
@end group
|
|
@end example
|
|
|
|
The function @code{read-key-sequence} suppresses quitting: @kbd{C-g}
|
|
typed while reading with this function works like any other character,
|
|
and does not set @code{quit-flag}. @xref{Quitting}.
|
|
@end defun
|
|
|
|
@defun read-key-sequence-vector prompt
|
|
This is like @code{read-key-sequence} except that it always
|
|
returns the key sequence as a vector, never as a string.
|
|
@xref{Strings of Events}.
|
|
@end defun
|
|
|
|
@cindex upper case key sequence
|
|
@cindex downcasing in @code{lookup-key}
|
|
If an input character is an upper-case letter and has no key binding,
|
|
but its lower-case equivalent has one, then @code{read-key-sequence}
|
|
converts the character to lower case. Note that @code{lookup-key} does
|
|
not perform case conversion in this way.
|
|
|
|
The function @code{read-key-sequence} also transforms some mouse events.
|
|
It converts unbound drag events into click events, and discards unbound
|
|
button-down events entirely. It also reshuffles focus events and
|
|
miscellaneous window events so that they never appear in a key sequence
|
|
with any other events.
|
|
|
|
@cindex @code{header-line} prefix key
|
|
@cindex @code{mode-line} prefix key
|
|
@cindex @code{vertical-line} prefix key
|
|
@cindex @code{horizontal-scroll-bar} prefix key
|
|
@cindex @code{vertical-scroll-bar} prefix key
|
|
@cindex @code{menu-bar} prefix key
|
|
@cindex mouse events, in special parts of frame
|
|
When mouse events occur in special parts of a window, such as a mode
|
|
line or a scroll bar, the event type shows nothing special---it is the
|
|
same symbol that would normally represent that combination of mouse
|
|
button and modifier keys. The information about the window part is kept
|
|
elsewhere in the event---in the coordinates. But
|
|
@code{read-key-sequence} translates this information into imaginary
|
|
``prefix keys'', all of which are symbols: @code{header-line},
|
|
@code{horizontal-scroll-bar}, @code{menu-bar}, @code{mode-line},
|
|
@code{vertical-line}, and @code{vertical-scroll-bar}. You can define
|
|
meanings for mouse clicks in special window parts by defining key
|
|
sequences using these imaginary prefix keys.
|
|
|
|
For example, if you call @code{read-key-sequence} and then click the
|
|
mouse on the window's mode line, you get two events, like this:
|
|
|
|
@example
|
|
(read-key-sequence "Click on the mode line: ")
|
|
@result{} [mode-line
|
|
(mouse-1
|
|
(#<window 6 on NEWS> mode-line
|
|
(40 . 63) 5959987))]
|
|
@end example
|
|
|
|
@defvar num-input-keys
|
|
@c Emacs 19 feature
|
|
This variable's value is the number of key sequences processed so far in
|
|
this Emacs session. This includes key sequences read from the terminal
|
|
and key sequences read from keyboard macros being executed.
|
|
@end defvar
|
|
|
|
@defvar num-nonmacro-input-events
|
|
This variable holds the total number of input events received so far
|
|
from the terminal---not counting those generated by keyboard macros.
|
|
@end defvar
|
|
|
|
@node Reading One Event
|
|
@subsection Reading One Event
|
|
@cindex reading a single event
|
|
@cindex event, reading only one
|
|
|
|
The lowest level functions for command input are those that read a
|
|
single event.
|
|
|
|
@defun read-event &optional prompt inherit-input-method
|
|
This function reads and returns the next event of command input, waiting
|
|
if necessary until an event is available. Events can come directly from
|
|
the user or from a keyboard macro.
|
|
|
|
If the optional argument @var{prompt} is non-@code{nil}, it should be a
|
|
string to display in the echo area as a prompt. Otherwise,
|
|
@code{read-event} does not display any message to indicate it is waiting
|
|
for input; instead, it prompts by echoing: it displays descriptions of
|
|
the events that led to or were read by the current command. @xref{The
|
|
Echo Area}.
|
|
|
|
If @var{inherit-input-method} is non-@code{nil}, then the current input
|
|
method (if any) is employed to make it possible to enter a
|
|
non-@acronym{ASCII} character. Otherwise, input method handling is disabled
|
|
for reading this event.
|
|
|
|
If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event}
|
|
moves the cursor temporarily to the echo area, to the end of any message
|
|
displayed there. Otherwise @code{read-event} does not move the cursor.
|
|
|
|
If @code{read-event} gets an event that is defined as a help character, in
|
|
some cases @code{read-event} processes the event directly without
|
|
returning. @xref{Help Functions}. Certain other events, called
|
|
@dfn{special events}, are also processed directly within
|
|
@code{read-event} (@pxref{Special Events}).
|
|
|
|
Here is what happens if you call @code{read-event} and then press the
|
|
right-arrow function key:
|
|
|
|
@example
|
|
@group
|
|
(read-event)
|
|
@result{} right
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun read-char &optional prompt inherit-input-method
|
|
This function reads and returns a character of command input. If the
|
|
user generates an event which is not a character (i.e. a mouse click or
|
|
function key event), @code{read-char} signals an error. The arguments
|
|
work as in @code{read-event}.
|
|
|
|
In the first example, the user types the character @kbd{1} (@acronym{ASCII}
|
|
code 49). The second example shows a keyboard macro definition that
|
|
calls @code{read-char} from the minibuffer using @code{eval-expression}.
|
|
@code{read-char} reads the keyboard macro's very next character, which
|
|
is @kbd{1}. Then @code{eval-expression} displays its return value in
|
|
the echo area.
|
|
|
|
@example
|
|
@group
|
|
(read-char)
|
|
@result{} 49
|
|
@end group
|
|
|
|
@group
|
|
;; @r{We assume here you use @kbd{M-:} to evaluate this.}
|
|
(symbol-function 'foo)
|
|
@result{} "^[:(read-char)^M1"
|
|
@end group
|
|
@group
|
|
(execute-kbd-macro 'foo)
|
|
@print{} 49
|
|
@result{} nil
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun read-char-exclusive &optional prompt inherit-input-method
|
|
This function reads and returns a character of command input. If the
|
|
user generates an event which is not a character,
|
|
@code{read-char-exclusive} ignores it and reads another event, until it
|
|
gets a character. The arguments work as in @code{read-event}.
|
|
@end defun
|
|
|
|
@node Invoking the Input Method
|
|
@subsection Invoking the Input Method
|
|
|
|
The event-reading functions invoke the current input method, if any
|
|
(@pxref{Input Methods}). If the value of @code{input-method-function}
|
|
is non-@code{nil}, it should be a function; when @code{read-event} reads
|
|
a printing character (including @key{SPC}) with no modifier bits, it
|
|
calls that function, passing the character as an argument.
|
|
|
|
@defvar input-method-function
|
|
If this is non-@code{nil}, its value specifies the current input method
|
|
function.
|
|
|
|
@strong{Warning:} don't bind this variable with @code{let}. It is often
|
|
buffer-local, and if you bind it around reading input (which is exactly
|
|
when you @emph{would} bind it), switching buffers asynchronously while
|
|
Emacs is waiting will cause the value to be restored in the wrong
|
|
buffer.
|
|
@end defvar
|
|
|
|
The input method function should return a list of events which should
|
|
be used as input. (If the list is @code{nil}, that means there is no
|
|
input, so @code{read-event} waits for another event.) These events are
|
|
processed before the events in @code{unread-command-events}
|
|
(@pxref{Event Input Misc}). Events
|
|
returned by the input method function are not passed to the input method
|
|
function again, even if they are printing characters with no modifier
|
|
bits.
|
|
|
|
If the input method function calls @code{read-event} or
|
|
@code{read-key-sequence}, it should bind @code{input-method-function} to
|
|
@code{nil} first, to prevent recursion.
|
|
|
|
The input method function is not called when reading the second and
|
|
subsequent events of a key sequence. Thus, these characters are not
|
|
subject to input method processing. The input method function should
|
|
test the values of @code{overriding-local-map} and
|
|
@code{overriding-terminal-local-map}; if either of these variables is
|
|
non-@code{nil}, the input method should put its argument into a list and
|
|
return that list with no further processing.
|
|
|
|
@node Quoted Character Input
|
|
@subsection Quoted Character Input
|
|
@cindex quoted character input
|
|
|
|
You can use the function @code{read-quoted-char} to ask the user to
|
|
specify a character, and allow the user to specify a control or meta
|
|
character conveniently, either literally or as an octal character code.
|
|
The command @code{quoted-insert} uses this function.
|
|
|
|
@defun read-quoted-char &optional prompt
|
|
@cindex octal character input
|
|
@cindex control characters, reading
|
|
@cindex nonprinting characters, reading
|
|
This function is like @code{read-char}, except that if the first
|
|
character read is an octal digit (0-7), it reads any number of octal
|
|
digits (but stopping if a non-octal digit is found), and returns the
|
|
character represented by that numeric character code.
|
|
|
|
Quitting is suppressed when the first character is read, so that the
|
|
user can enter a @kbd{C-g}. @xref{Quitting}.
|
|
|
|
If @var{prompt} is supplied, it specifies a string for prompting the
|
|
user. The prompt string is always displayed in the echo area, followed
|
|
by a single @samp{-}.
|
|
|
|
In the following example, the user types in the octal number 177 (which
|
|
is 127 in decimal).
|
|
|
|
@example
|
|
(read-quoted-char "What character")
|
|
|
|
@group
|
|
---------- Echo Area ----------
|
|
What character-@kbd{177}
|
|
---------- Echo Area ----------
|
|
|
|
@result{} 127
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@need 2000
|
|
@node Event Input Misc
|
|
@subsection Miscellaneous Event Input Features
|
|
|
|
This section describes how to ``peek ahead'' at events without using
|
|
them up, how to check for pending input, and how to discard pending
|
|
input. See also the function @code{read-passwd} (@pxref{Reading a
|
|
Password}).
|
|
|
|
@defvar unread-command-events
|
|
@cindex next input
|
|
@cindex peeking at input
|
|
This variable holds a list of events waiting to be read as command
|
|
input. The events are used in the order they appear in the list, and
|
|
removed one by one as they are used.
|
|
|
|
The variable is needed because in some cases a function reads an event
|
|
and then decides not to use it. Storing the event in this variable
|
|
causes it to be processed normally, by the command loop or by the
|
|
functions to read command input.
|
|
|
|
@cindex prefix argument unreading
|
|
For example, the function that implements numeric prefix arguments reads
|
|
any number of digits. When it finds a non-digit event, it must unread
|
|
the event so that it can be read normally by the command loop.
|
|
Likewise, incremental search uses this feature to unread events with no
|
|
special meaning in a search, because these events should exit the search
|
|
and then execute normally.
|
|
|
|
The reliable and easy way to extract events from a key sequence so as to
|
|
put them in @code{unread-command-events} is to use
|
|
@code{listify-key-sequence} (@pxref{Strings of Events}).
|
|
|
|
Normally you add events to the front of this list, so that the events
|
|
most recently unread will be reread first.
|
|
@end defvar
|
|
|
|
@defun listify-key-sequence key
|
|
This function converts the string or vector @var{key} to a list of
|
|
individual events, which you can put in @code{unread-command-events}.
|
|
@end defun
|
|
|
|
@defvar unread-command-char
|
|
This variable holds a character to be read as command input.
|
|
A value of -1 means ``empty''.
|
|
|
|
This variable is mostly obsolete now that you can use
|
|
@code{unread-command-events} instead; it exists only to support programs
|
|
written for Emacs versions 18 and earlier.
|
|
@end defvar
|
|
|
|
@defun input-pending-p
|
|
@cindex waiting for command key input
|
|
This function determines whether any command input is currently
|
|
available to be read. It returns immediately, with value @code{t} if
|
|
there is available input, @code{nil} otherwise. On rare occasions it
|
|
may return @code{t} when no input is available.
|
|
@end defun
|
|
|
|
@defvar last-input-event
|
|
@defvarx last-input-char
|
|
This variable records the last terminal input event read, whether
|
|
as part of a command or explicitly by a Lisp program.
|
|
|
|
In the example below, the Lisp program reads the character @kbd{1},
|
|
@acronym{ASCII} code 49. It becomes the value of @code{last-input-event},
|
|
while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate
|
|
this expression) remains the value of @code{last-command-event}.
|
|
|
|
@example
|
|
@group
|
|
(progn (print (read-char))
|
|
(print last-command-event)
|
|
last-input-event)
|
|
@print{} 49
|
|
@print{} 5
|
|
@result{} 49
|
|
@end group
|
|
@end example
|
|
|
|
The alias @code{last-input-char} exists for compatibility with
|
|
Emacs version 18.
|
|
@end defvar
|
|
|
|
@defun discard-input
|
|
@cindex flush input
|
|
@cindex discard input
|
|
@cindex terminate keyboard macro
|
|
This function discards the contents of the terminal input buffer and
|
|
cancels any keyboard macro that might be in the process of definition.
|
|
It returns @code{nil}.
|
|
|
|
In the following example, the user may type a number of characters right
|
|
after starting the evaluation of the form. After the @code{sleep-for}
|
|
finishes sleeping, @code{discard-input} discards any characters typed
|
|
during the sleep.
|
|
|
|
@example
|
|
(progn (sleep-for 2)
|
|
(discard-input))
|
|
@result{} nil
|
|
@end example
|
|
@end defun
|
|
|
|
@node Special Events
|
|
@section Special Events
|
|
|
|
@cindex special events
|
|
Special events are handled at a very low level---as soon as they are
|
|
read. The @code{read-event} function processes these events itself, and
|
|
never returns them.
|
|
|
|
Events that are handled in this way do not echo, they are never grouped
|
|
into key sequences, and they never appear in the value of
|
|
@code{last-command-event} or @code{(this-command-keys)}. They do not
|
|
discard a numeric argument, they cannot be unread with
|
|
@code{unread-command-events}, they may not appear in a keyboard macro,
|
|
and they are not recorded in a keyboard macro while you are defining
|
|
one.
|
|
|
|
These events do, however, appear in @code{last-input-event} immediately
|
|
after they are read, and this is the way for the event's definition to
|
|
find the actual event.
|
|
|
|
The events types @code{iconify-frame}, @code{make-frame-visible} and
|
|
@code{delete-frame} are normally handled in this way. The keymap which
|
|
defines how to handle special events---and which events are special---is
|
|
in the variable @code{special-event-map} (@pxref{Active Keymaps}).
|
|
|
|
@node Waiting
|
|
@section Waiting for Elapsed Time or Input
|
|
@cindex pausing
|
|
@cindex waiting
|
|
|
|
The wait functions are designed to wait for a certain amount of time
|
|
to pass or until there is input. For example, you may wish to pause in
|
|
the middle of a computation to allow the user time to view the display.
|
|
@code{sit-for} pauses and updates the screen, and returns immediately if
|
|
input comes in, while @code{sleep-for} pauses without updating the
|
|
screen.
|
|
|
|
@defun sit-for seconds &optional nodisp
|
|
This function performs redisplay (provided there is no pending input
|
|
from the user), then waits @var{seconds} seconds, or until input is
|
|
available. The value is @code{t} if @code{sit-for} waited the full
|
|
time with no input arriving (see @code{input-pending-p} in @ref{Event
|
|
Input Misc}). Otherwise, the value is @code{nil}.
|
|
|
|
The argument @var{seconds} need not be an integer. If it is a floating
|
|
point number, @code{sit-for} waits for a fractional number of seconds.
|
|
Some systems support only a whole number of seconds; on these systems,
|
|
@var{seconds} is rounded down.
|
|
|
|
The expression @code{(sit-for 0)} is a convenient way to request a
|
|
redisplay, without any delay. @xref{Forcing Redisplay}.
|
|
|
|
If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not
|
|
redisplay, but it still returns as soon as input is available (or when
|
|
the timeout elapses).
|
|
|
|
Iconifying or deiconifying a frame makes @code{sit-for} return, because
|
|
that generates an event. @xref{Misc Events}.
|
|
|
|
The usual purpose of @code{sit-for} is to give the user time to read
|
|
text that you display.
|
|
|
|
It is also possible to call @code{sit-for} with three arguments,
|
|
as @code{(sit-for @var{seconds} @var{millisec} @var{nodisp})},
|
|
but that is considered obsolete.
|
|
@end defun
|
|
|
|
@defun sleep-for seconds &optional millisec
|
|
This function simply pauses for @var{seconds} seconds without updating
|
|
the display. It pays no attention to available input. It returns
|
|
@code{nil}.
|
|
|
|
The argument @var{seconds} need not be an integer. If it is a floating
|
|
point number, @code{sleep-for} waits for a fractional number of seconds.
|
|
Some systems support only a whole number of seconds; on these systems,
|
|
@var{seconds} is rounded down.
|
|
|
|
The optional argument @var{millisec} specifies an additional waiting
|
|
period measured in milliseconds. This adds to the period specified by
|
|
@var{seconds}. If the system doesn't support waiting fractions of a
|
|
second, you get an error if you specify nonzero @var{millisec}.
|
|
|
|
Use @code{sleep-for} when you wish to guarantee a delay.
|
|
@end defun
|
|
|
|
@xref{Time of Day}, for functions to get the current time.
|
|
|
|
@node Quitting
|
|
@section Quitting
|
|
@cindex @kbd{C-g}
|
|
@cindex quitting
|
|
@cindex interrupt Lisp functions
|
|
|
|
Typing @kbd{C-g} while a Lisp function is running causes Emacs to
|
|
@dfn{quit} whatever it is doing. This means that control returns to the
|
|
innermost active command loop.
|
|
|
|
Typing @kbd{C-g} while the command loop is waiting for keyboard input
|
|
does not cause a quit; it acts as an ordinary input character. In the
|
|
simplest case, you cannot tell the difference, because @kbd{C-g}
|
|
normally runs the command @code{keyboard-quit}, whose effect is to quit.
|
|
However, when @kbd{C-g} follows a prefix key, they combine to form an
|
|
undefined key. The effect is to cancel the prefix key as well as any
|
|
prefix argument.
|
|
|
|
In the minibuffer, @kbd{C-g} has a different definition: it aborts out
|
|
of the minibuffer. This means, in effect, that it exits the minibuffer
|
|
and then quits. (Simply quitting would return to the command loop
|
|
@emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit
|
|
directly when the command reader is reading input is so that its meaning
|
|
can be redefined in the minibuffer in this way. @kbd{C-g} following a
|
|
prefix key is not redefined in the minibuffer, and it has its normal
|
|
effect of canceling the prefix key and prefix argument. This too
|
|
would not be possible if @kbd{C-g} always quit directly.
|
|
|
|
When @kbd{C-g} does directly quit, it does so by setting the variable
|
|
@code{quit-flag} to @code{t}. Emacs checks this variable at appropriate
|
|
times and quits if it is not @code{nil}. Setting @code{quit-flag}
|
|
non-@code{nil} in any way thus causes a quit.
|
|
|
|
At the level of C code, quitting cannot happen just anywhere; only at the
|
|
special places that check @code{quit-flag}. The reason for this is
|
|
that quitting at other places might leave an inconsistency in Emacs's
|
|
internal state. Because quitting is delayed until a safe place, quitting
|
|
cannot make Emacs crash.
|
|
|
|
Certain functions such as @code{read-key-sequence} or
|
|
@code{read-quoted-char} prevent quitting entirely even though they wait
|
|
for input. Instead of quitting, @kbd{C-g} serves as the requested
|
|
input. In the case of @code{read-key-sequence}, this serves to bring
|
|
about the special behavior of @kbd{C-g} in the command loop. In the
|
|
case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used
|
|
to quote a @kbd{C-g}.
|
|
|
|
@cindex prevent quitting
|
|
You can prevent quitting for a portion of a Lisp function by binding
|
|
the variable @code{inhibit-quit} to a non-@code{nil} value. Then,
|
|
although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the
|
|
usual result of this---a quit---is prevented. Eventually,
|
|
@code{inhibit-quit} will become @code{nil} again, such as when its
|
|
binding is unwound at the end of a @code{let} form. At that time, if
|
|
@code{quit-flag} is still non-@code{nil}, the requested quit happens
|
|
immediately. This behavior is ideal when you wish to make sure that
|
|
quitting does not happen within a ``critical section'' of the program.
|
|
|
|
@cindex @code{read-quoted-char} quitting
|
|
In some functions (such as @code{read-quoted-char}), @kbd{C-g} is
|
|
handled in a special way that does not involve quitting. This is done
|
|
by reading the input with @code{inhibit-quit} bound to @code{t}, and
|
|
setting @code{quit-flag} to @code{nil} before @code{inhibit-quit}
|
|
becomes @code{nil} again. This excerpt from the definition of
|
|
@code{read-quoted-char} shows how this is done; it also shows that
|
|
normal quitting is permitted after the first character of input.
|
|
|
|
@example
|
|
(defun read-quoted-char (&optional prompt)
|
|
"@dots{}@var{documentation}@dots{}"
|
|
(let ((message-log-max nil) done (first t) (code 0) char)
|
|
(while (not done)
|
|
(let ((inhibit-quit first)
|
|
@dots{})
|
|
(and prompt (message "%s-" prompt))
|
|
(setq char (read-event))
|
|
(if inhibit-quit (setq quit-flag nil)))
|
|
@r{@dots{}set the variable @code{code}@dots{}})
|
|
code))
|
|
@end example
|
|
|
|
@defvar quit-flag
|
|
If this variable is non-@code{nil}, then Emacs quits immediately, unless
|
|
@code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets
|
|
@code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}.
|
|
@end defvar
|
|
|
|
@defvar inhibit-quit
|
|
This variable determines whether Emacs should quit when @code{quit-flag}
|
|
is set to a value other than @code{nil}. If @code{inhibit-quit} is
|
|
non-@code{nil}, then @code{quit-flag} has no special effect.
|
|
@end defvar
|
|
|
|
@deffn Command keyboard-quit
|
|
This function signals the @code{quit} condition with @code{(signal 'quit
|
|
nil)}. This is the same thing that quitting does. (See @code{signal}
|
|
in @ref{Errors}.)
|
|
@end deffn
|
|
|
|
You can specify a character other than @kbd{C-g} to use for quitting.
|
|
See the function @code{set-input-mode} in @ref{Terminal Input}.
|
|
|
|
@node Prefix Command Arguments
|
|
@section Prefix Command Arguments
|
|
@cindex prefix argument
|
|
@cindex raw prefix argument
|
|
@cindex numeric prefix argument
|
|
|
|
Most Emacs commands can use a @dfn{prefix argument}, a number
|
|
specified before the command itself. (Don't confuse prefix arguments
|
|
with prefix keys.) The prefix argument is at all times represented by a
|
|
value, which may be @code{nil}, meaning there is currently no prefix
|
|
argument. Each command may use the prefix argument or ignore it.
|
|
|
|
There are two representations of the prefix argument: @dfn{raw} and
|
|
@dfn{numeric}. The editor command loop uses the raw representation
|
|
internally, and so do the Lisp variables that store the information, but
|
|
commands can request either representation.
|
|
|
|
Here are the possible values of a raw prefix argument:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
@code{nil}, meaning there is no prefix argument. Its numeric value is
|
|
1, but numerous commands make a distinction between @code{nil} and the
|
|
integer 1.
|
|
|
|
@item
|
|
An integer, which stands for itself.
|
|
|
|
@item
|
|
A list of one element, which is an integer. This form of prefix
|
|
argument results from one or a succession of @kbd{C-u}'s with no
|
|
digits. The numeric value is the integer in the list, but some
|
|
commands make a distinction between such a list and an integer alone.
|
|
|
|
@item
|
|
The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was
|
|
typed, without following digits. The equivalent numeric value is
|
|
@minus{}1, but some commands make a distinction between the integer
|
|
@minus{}1 and the symbol @code{-}.
|
|
@end itemize
|
|
|
|
We illustrate these possibilities by calling the following function with
|
|
various prefixes:
|
|
|
|
@example
|
|
@group
|
|
(defun display-prefix (arg)
|
|
"Display the value of the raw prefix arg."
|
|
(interactive "P")
|
|
(message "%s" arg))
|
|
@end group
|
|
@end example
|
|
|
|
@noindent
|
|
Here are the results of calling @code{display-prefix} with various
|
|
raw prefix arguments:
|
|
|
|
@example
|
|
M-x display-prefix @print{} nil
|
|
|
|
C-u M-x display-prefix @print{} (4)
|
|
|
|
C-u C-u M-x display-prefix @print{} (16)
|
|
|
|
C-u 3 M-x display-prefix @print{} 3
|
|
|
|
M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)}
|
|
|
|
C-u - M-x display-prefix @print{} -
|
|
|
|
M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)}
|
|
|
|
C-u - 7 M-x display-prefix @print{} -7
|
|
|
|
M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)}
|
|
@end example
|
|
|
|
Emacs uses two variables to store the prefix argument:
|
|
@code{prefix-arg} and @code{current-prefix-arg}. Commands such as
|
|
@code{universal-argument} that set up prefix arguments for other
|
|
commands store them in @code{prefix-arg}. In contrast,
|
|
@code{current-prefix-arg} conveys the prefix argument to the current
|
|
command, so setting it has no effect on the prefix arguments for future
|
|
commands.
|
|
|
|
Normally, commands specify which representation to use for the prefix
|
|
argument, either numeric or raw, in the @code{interactive} declaration.
|
|
(@xref{Using Interactive}.) Alternatively, functions may look at the
|
|
value of the prefix argument directly in the variable
|
|
@code{current-prefix-arg}, but this is less clean.
|
|
|
|
@defun prefix-numeric-value arg
|
|
This function returns the numeric meaning of a valid raw prefix argument
|
|
value, @var{arg}. The argument may be a symbol, a number, or a list.
|
|
If it is @code{nil}, the value 1 is returned; if it is @code{-}, the
|
|
value @minus{}1 is returned; if it is a number, that number is returned;
|
|
if it is a list, the @sc{car} of that list (which should be a number) is
|
|
returned.
|
|
@end defun
|
|
|
|
@defvar current-prefix-arg
|
|
This variable holds the raw prefix argument for the @emph{current}
|
|
command. Commands may examine it directly, but the usual method for
|
|
accessing it is with @code{(interactive "P")}.
|
|
@end defvar
|
|
|
|
@defvar prefix-arg
|
|
The value of this variable is the raw prefix argument for the
|
|
@emph{next} editing command. Commands such as @code{universal-argument}
|
|
that specify prefix arguments for the following command work by setting
|
|
this variable.
|
|
@end defvar
|
|
|
|
@defvar last-prefix-arg
|
|
The raw prefix argument value used by the previous command.
|
|
@end defvar
|
|
|
|
The following commands exist to set up prefix arguments for the
|
|
following command. Do not call them for any other reason.
|
|
|
|
@deffn Command universal-argument
|
|
This command reads input and specifies a prefix argument for the
|
|
following command. Don't call this command yourself unless you know
|
|
what you are doing.
|
|
@end deffn
|
|
|
|
@deffn Command digit-argument arg
|
|
This command adds to the prefix argument for the following command. The
|
|
argument @var{arg} is the raw prefix argument as it was before this
|
|
command; it is used to compute the updated prefix argument. Don't call
|
|
this command yourself unless you know what you are doing.
|
|
@end deffn
|
|
|
|
@deffn Command negative-argument arg
|
|
This command adds to the numeric argument for the next command. The
|
|
argument @var{arg} is the raw prefix argument as it was before this
|
|
command; its value is negated to form the new prefix argument. Don't
|
|
call this command yourself unless you know what you are doing.
|
|
@end deffn
|
|
|
|
@node Recursive Editing
|
|
@section Recursive Editing
|
|
@cindex recursive command loop
|
|
@cindex recursive editing level
|
|
@cindex command loop, recursive
|
|
|
|
The Emacs command loop is entered automatically when Emacs starts up.
|
|
This top-level invocation of the command loop never exits; it keeps
|
|
running as long as Emacs does. Lisp programs can also invoke the
|
|
command loop. Since this makes more than one activation of the command
|
|
loop, we call it @dfn{recursive editing}. A recursive editing level has
|
|
the effect of suspending whatever command invoked it and permitting the
|
|
user to do arbitrary editing before resuming that command.
|
|
|
|
The commands available during recursive editing are the same ones
|
|
available in the top-level editing loop and defined in the keymaps.
|
|
Only a few special commands exit the recursive editing level; the others
|
|
return to the recursive editing level when they finish. (The special
|
|
commands for exiting are always available, but they do nothing when
|
|
recursive editing is not in progress.)
|
|
|
|
All command loops, including recursive ones, set up all-purpose error
|
|
handlers so that an error in a command run from the command loop will
|
|
not exit the loop.
|
|
|
|
@cindex minibuffer input
|
|
Minibuffer input is a special kind of recursive editing. It has a few
|
|
special wrinkles, such as enabling display of the minibuffer and the
|
|
minibuffer window, but fewer than you might suppose. Certain keys
|
|
behave differently in the minibuffer, but that is only because of the
|
|
minibuffer's local map; if you switch windows, you get the usual Emacs
|
|
commands.
|
|
|
|
@cindex @code{throw} example
|
|
@kindex exit
|
|
@cindex exit recursive editing
|
|
@cindex aborting
|
|
To invoke a recursive editing level, call the function
|
|
@code{recursive-edit}. This function contains the command loop; it also
|
|
contains a call to @code{catch} with tag @code{exit}, which makes it
|
|
possible to exit the recursive editing level by throwing to @code{exit}
|
|
(@pxref{Catch and Throw}). If you throw a value other than @code{t},
|
|
then @code{recursive-edit} returns normally to the function that called
|
|
it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this.
|
|
Throwing a @code{t} value causes @code{recursive-edit} to quit, so that
|
|
control returns to the command loop one level up. This is called
|
|
@dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}).
|
|
|
|
Most applications should not use recursive editing, except as part of
|
|
using the minibuffer. Usually it is more convenient for the user if you
|
|
change the major mode of the current buffer temporarily to a special
|
|
major mode, which should have a command to go back to the previous mode.
|
|
(The @kbd{e} command in Rmail uses this technique.) Or, if you wish to
|
|
give the user different text to edit ``recursively'', create and select
|
|
a new buffer in a special mode. In this mode, define a command to
|
|
complete the processing and go back to the previous buffer. (The
|
|
@kbd{m} command in Rmail does this.)
|
|
|
|
Recursive edits are useful in debugging. You can insert a call to
|
|
@code{debug} into a function definition as a sort of breakpoint, so that
|
|
you can look around when the function gets there. @code{debug} invokes
|
|
a recursive edit but also provides the other features of the debugger.
|
|
|
|
Recursive editing levels are also used when you type @kbd{C-r} in
|
|
@code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}).
|
|
|
|
@defun recursive-edit
|
|
@cindex suspend evaluation
|
|
This function invokes the editor command loop. It is called
|
|
automatically by the initialization of Emacs, to let the user begin
|
|
editing. When called from a Lisp program, it enters a recursive editing
|
|
level.
|
|
|
|
In the following example, the function @code{simple-rec} first
|
|
advances point one word, then enters a recursive edit, printing out a
|
|
message in the echo area. The user can then do any editing desired, and
|
|
then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}.
|
|
|
|
@example
|
|
(defun simple-rec ()
|
|
(forward-word 1)
|
|
(message "Recursive edit in progress")
|
|
(recursive-edit)
|
|
(forward-word 1))
|
|
@result{} simple-rec
|
|
(simple-rec)
|
|
@result{} nil
|
|
@end example
|
|
@end defun
|
|
|
|
@deffn Command exit-recursive-edit
|
|
This function exits from the innermost recursive edit (including
|
|
minibuffer input). Its definition is effectively @code{(throw 'exit
|
|
nil)}.
|
|
@end deffn
|
|
|
|
@deffn Command abort-recursive-edit
|
|
This function aborts the command that requested the innermost recursive
|
|
edit (including minibuffer input), by signaling @code{quit}
|
|
after exiting the recursive edit. Its definition is effectively
|
|
@code{(throw 'exit t)}. @xref{Quitting}.
|
|
@end deffn
|
|
|
|
@deffn Command top-level
|
|
This function exits all recursive editing levels; it does not return a
|
|
value, as it jumps completely out of any computation directly back to
|
|
the main command loop.
|
|
@end deffn
|
|
|
|
@defun recursion-depth
|
|
This function returns the current depth of recursive edits. When no
|
|
recursive edit is active, it returns 0.
|
|
@end defun
|
|
|
|
@node Disabling Commands
|
|
@section Disabling Commands
|
|
@cindex disabled command
|
|
|
|
@dfn{Disabling a command} marks the command as requiring user
|
|
confirmation before it can be executed. Disabling is used for commands
|
|
which might be confusing to beginning users, to prevent them from using
|
|
the commands by accident.
|
|
|
|
@kindex disabled
|
|
The low-level mechanism for disabling a command is to put a
|
|
non-@code{nil} @code{disabled} property on the Lisp symbol for the
|
|
command. These properties are normally set up by the user's
|
|
init file (@pxref{Init File}) with Lisp expressions such as this:
|
|
|
|
@example
|
|
(put 'upcase-region 'disabled t)
|
|
@end example
|
|
|
|
@noindent
|
|
For a few commands, these properties are present by default (you can
|
|
remove them in your init file if you wish).
|
|
|
|
If the value of the @code{disabled} property is a string, the message
|
|
saying the command is disabled includes that string. For example:
|
|
|
|
@example
|
|
(put 'delete-region 'disabled
|
|
"Text deleted this way cannot be yanked back!\n")
|
|
@end example
|
|
|
|
@xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on
|
|
what happens when a disabled command is invoked interactively.
|
|
Disabling a command has no effect on calling it as a function from Lisp
|
|
programs.
|
|
|
|
@deffn Command enable-command command
|
|
Allow @var{command} to be executed without special confirmation from now
|
|
on, and (if the user confirms) alter the user's init file (@pxref{Init
|
|
File}) so that this will apply to future sessions.
|
|
@end deffn
|
|
|
|
@deffn Command disable-command command
|
|
Require special confirmation to execute @var{command} from now on, and
|
|
(if the user confirms) alter the user's init file so that this
|
|
will apply to future sessions.
|
|
@end deffn
|
|
|
|
@defvar disabled-command-hook
|
|
When the user invokes a disabled command interactively, this normal hook
|
|
is run instead of the disabled command. The hook functions can use
|
|
@code{this-command-keys} to determine what the user typed to run the
|
|
command, and thus find the command itself. @xref{Hooks}.
|
|
|
|
By default, @code{disabled-command-hook} contains a function that asks
|
|
the user whether to proceed.
|
|
@end defvar
|
|
|
|
@node Command History
|
|
@section Command History
|
|
@cindex command history
|
|
@cindex complex command
|
|
@cindex history of commands
|
|
|
|
The command loop keeps a history of the complex commands that have
|
|
been executed, to make it convenient to repeat these commands. A
|
|
@dfn{complex command} is one for which the interactive argument reading
|
|
uses the minibuffer. This includes any @kbd{M-x} command, any
|
|
@kbd{M-:} command, and any command whose @code{interactive}
|
|
specification reads an argument from the minibuffer. Explicit use of
|
|
the minibuffer during the execution of the command itself does not cause
|
|
the command to be considered complex.
|
|
|
|
@defvar command-history
|
|
This variable's value is a list of recent complex commands, each
|
|
represented as a form to evaluate. It continues to accumulate all
|
|
complex commands for the duration of the editing session, but when it
|
|
reaches the maximum size (@pxref{Minibuffer History}), the oldest
|
|
elements are deleted as new ones are added.
|
|
|
|
@example
|
|
@group
|
|
command-history
|
|
@result{} ((switch-to-buffer "chistory.texi")
|
|
(describe-key "^X^[")
|
|
(visit-tags-table "~/emacs/src/")
|
|
(find-tag "repeat-complex-command"))
|
|
@end group
|
|
@end example
|
|
@end defvar
|
|
|
|
This history list is actually a special case of minibuffer history
|
|
(@pxref{Minibuffer History}), with one special twist: the elements are
|
|
expressions rather than strings.
|
|
|
|
There are a number of commands devoted to the editing and recall of
|
|
previous commands. The commands @code{repeat-complex-command}, and
|
|
@code{list-command-history} are described in the user manual
|
|
(@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the
|
|
minibuffer, the usual minibuffer history commands are available.
|
|
|
|
@node Keyboard Macros
|
|
@section Keyboard Macros
|
|
@cindex keyboard macros
|
|
|
|
A @dfn{keyboard macro} is a canned sequence of input events that can
|
|
be considered a command and made the definition of a key. The Lisp
|
|
representation of a keyboard macro is a string or vector containing the
|
|
events. Don't confuse keyboard macros with Lisp macros
|
|
(@pxref{Macros}).
|
|
|
|
@defun execute-kbd-macro kbdmacro &optional count
|
|
This function executes @var{kbdmacro} as a sequence of events. If
|
|
@var{kbdmacro} is a string or vector, then the events in it are executed
|
|
exactly as if they had been input by the user. The sequence is
|
|
@emph{not} expected to be a single key sequence; normally a keyboard
|
|
macro definition consists of several key sequences concatenated.
|
|
|
|
If @var{kbdmacro} is a symbol, then its function definition is used in
|
|
place of @var{kbdmacro}. If that is another symbol, this process repeats.
|
|
Eventually the result should be a string or vector. If the result is
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|
not a symbol, string, or vector, an error is signaled.
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|
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The argument @var{count} is a repeat count; @var{kbdmacro} is executed that
|
|
many times. If @var{count} is omitted or @code{nil}, @var{kbdmacro} is
|
|
executed once. If it is 0, @var{kbdmacro} is executed over and over until it
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|
encounters an error or a failing search.
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|
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|
@xref{Reading One Event}, for an example of using @code{execute-kbd-macro}.
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|
@end defun
|
|
|
|
@defvar executing-macro
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|
This variable contains the string or vector that defines the keyboard
|
|
macro that is currently executing. It is @code{nil} if no macro is
|
|
currently executing. A command can test this variable so as to behave
|
|
differently when run from an executing macro. Do not set this variable
|
|
yourself.
|
|
@end defvar
|
|
|
|
@defvar defining-kbd-macro
|
|
This variable indicates whether a keyboard macro is being defined. A
|
|
command can test this variable so as to behave differently while a macro
|
|
is being defined. The commands @code{start-kbd-macro} and
|
|
@code{end-kbd-macro} set this variable---do not set it yourself.
|
|
|
|
The variable is always local to the current terminal and cannot be
|
|
buffer-local. @xref{Multiple Displays}.
|
|
@end defvar
|
|
|
|
@defvar last-kbd-macro
|
|
This variable is the definition of the most recently defined keyboard
|
|
macro. Its value is a string or vector, or @code{nil}.
|
|
|
|
The variable is always local to the current terminal and cannot be
|
|
buffer-local. @xref{Multiple Displays}.
|
|
@end defvar
|
|
|
|
@defvar kbd-macro-termination-hook
|
|
This normal hook (@pxref{Standard Hooks}) is run when a keyboard
|
|
macro terminates, regardless of what caused it to terminate (reaching
|
|
the macro end or an error which ended the macro prematurely).
|
|
@end defvar
|
|
|
|
@ignore
|
|
arch-tag: e34944ad-7d5c-4980-be00-36a5fe54d4b1
|
|
@end ignore
|