@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1999
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1999, 2002, 2003, 2004,
+@c 2005, 2006 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/abbrevs
@node Abbrevs, Processes, Syntax Tables, Top
@end deffn
@deffn Command abbrev-prefix-mark &optional arg
-This command marks current point as the beginning of an abbrev. The
-next call to @code{expand-abbrev} will use the text from here to point
-(where it is then) as the abbrev to expand, rather than using the
-previous word as usual.
+This command marks the current location of point as the beginning of
+an abbrev. The next call to @code{expand-abbrev} will use the text
+from here to point (where it is then) as the abbrev to expand, rather
+than using the previous word as usual.
First, this command expands any abbrev before point, unless @var{arg}
is non-@code{nil}. (Interactively, @var{arg} is the prefix argument.)
@end defopt
@defvar abbrev-start-location
-This is a marker pointing to the buffer position for
-@code{expand-abbrev} to use as the start of the next abbrev to be
-expanded. (@code{nil} means use the word before point instead.)
-@code{abbrev-start-location} is set to @code{nil} each time
-@code{expand-abbrev} is called. This variable is also set by
-@code{abbrev-prefix-mark}.
+The value of this variable is a buffer position (an integer or a marker)
+for @code{expand-abbrev} to use as the start of the next abbrev to be
+expanded. The value can also be @code{nil}, which means to use the
+word before point instead. @code{abbrev-start-location} is set to
+@code{nil} each time @code{expand-abbrev} is called. This variable is
+also set by @code{abbrev-prefix-mark}.
@end defvar
@defvar abbrev-start-location-buffer
the abbrev to be expanded by looking in the buffer before point.
Running the hook is the first thing that @code{expand-abbrev} does, and
so a hook function can be used to change the current abbrev table before
-abbrev lookup happens.
+abbrev lookup happens. (Although you have to do this carefully. See
+the example below.)
@end defvar
The following sample code shows a simple use of
-@code{pre-abbrev-expand-hook}. If the user terminates an abbrev with a
-punctuation character, the hook function asks for confirmation. Thus,
-this hook allows the user to decide whether to expand the abbrev, and
-aborts expansion if it is not confirmed.
+@code{pre-abbrev-expand-hook}. It assumes that @code{foo-mode} is a
+mode for editing certain files in which lines that start with @samp{#}
+are comments. You want to use Text mode abbrevs for those lines. The
+regular local abbrev table, @code{foo-mode-abbrev-table} is
+appropriate for all other lines. Then you can put the following code
+in your @file{.emacs} file. @xref{Standard Abbrev Tables}, for the
+definitions of @code{local-abbrev-table} and @code{text-mode-abbrev-table}.
@smallexample
-(add-hook 'pre-abbrev-expand-hook 'query-if-not-space)
-
-;; @r{This is the function invoked by @code{pre-abbrev-expand-hook}.}
-
-;; @r{If the user terminated the abbrev with a space, the function does}
-;; @r{nothing (that is, it returns so that the abbrev can expand). If the}
-;; @r{user entered some other character, this function asks whether}
-;; @r{expansion should continue.}
-
-;; @r{If the user answers the prompt with @kbd{y}, the function returns}
-;; @r{@code{nil} (because of the @code{not} function), but that is}
-;; @r{acceptable; the return value has no effect on expansion.}
-
-(defun query-if-not-space ()
- (if (/= ?\s (preceding-char))
- (if (not (y-or-n-p "Do you want to expand this abbrev? "))
- (error "Not expanding this abbrev"))))
+(defun foo-mode-pre-abbrev-expand ()
+ (when (save-excursion (forward-line 0) (eq (char-after) ?#))
+ (let ((local-abbrev-table text-mode-abbrev-table)
+ ;; Avoid infinite loop.
+ (pre-abbrev-expand-hook nil))
+ (expand-abbrev))
+ ;; We have already called `expand-abbrev' in this hook.
+ ;; Hence we want the "actual" call following this hook to be a no-op.
+ (setq abbrev-start-location (point-max)
+ abbrev-start-location-buffer (current-buffer))))
+
+(add-hook 'foo-mode-hook
+ #'(lambda ()
+ (add-hook 'pre-abbrev-expand-hook
+ 'foo-mode-pre-abbrev-expand
+ nil t)))
@end smallexample
+Note that @code{foo-mode-pre-abbrev-expand} just returns @code{nil}
+without doing anything for lines not starting with @samp{#}. Hence
+abbrevs expand normally using @code{foo-mode-abbrev-table} as local
+abbrev table for such lines.
+
@node Standard Abbrev Tables, , Abbrev Expansion, Abbrevs
@comment node-name, next, previous, up
@section Standard Abbrev Tables