@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, 2003,
+@c 2004, 2005, 2006 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/markers
@node Markers, Text, Positions, Top
@node Overview of Markers
@section Overview of Markers
- A marker specifies a buffer and a position in that buffer. The marker
-can be used to represent a position in the functions that require one,
-just as an integer could be used. @xref{Positions}, for a complete
-description of positions.
-
- A marker has two attributes: the marker position, and the marker
-buffer. The marker position is an integer that is equivalent (at a
-given time) to the marker as a position in that buffer. But the
-marker's position value can change often during the life of the marker.
-Insertion and deletion of text in the buffer relocate the marker. The
-idea is that a marker positioned between two characters remains between
-those two characters despite insertion and deletion elsewhere in the
-buffer. Relocation changes the integer equivalent of the marker.
+ A marker specifies a buffer and a position in that buffer. The
+marker can be used to represent a position in the functions that
+require one, just as an integer could be used. In that case, the
+marker's buffer is normally ignored. Of course, a marker used in this
+way usually points to a position in the buffer that the function
+operates on, but that is entirely the programmer's responsibility.
+@xref{Positions}, for a complete description of positions.
+
+ A marker has three attributes: the marker position, the marker
+buffer, and the insertion type. The marker position is an integer
+that is equivalent (at a given time) to the marker as a position in
+that buffer. But the marker's position value can change often during
+the life of the marker. Insertion and deletion of text in the buffer
+relocate the marker. The idea is that a marker positioned between two
+characters remains between those two characters despite insertion and
+deletion elsewhere in the buffer. Relocation changes the integer
+equivalent of the marker.
@cindex marker relocation
Deleting text around a marker's position leaves the marker between the
@end defun
@node Creating Markers
-@section Functions That Create Markers
+@section Functions that Create Markers
When you create a new marker, you can make it point nowhere, or point
to the present position of point, or to the beginning or end of the
accessible portion of the buffer, or to the same place as another given
marker.
+The next four functions all return markers with insertion type
+@code{nil}. @xref{Marker Insertion Types}.
+
@defun make-marker
This function returns a newly created marker that does not point
anywhere.
@end example
@end defun
-@defun copy-marker marker-or-integer insertion-type
+@defun copy-marker marker-or-integer &optional insertion-type
If passed a marker as its argument, @code{copy-marker} returns a
new marker that points to the same place and the same buffer as does
@var{marker-or-integer}. If passed an integer as its argument,
@end example
@end defun
+@defun buffer-has-markers-at position
+@tindex buffer-has-markers-at
+This function returns @code{t} if one or more markers
+point at position @var{position} in the current buffer.
+@end defun
+
@node Marker Insertion Types
@section Marker Insertion Types
relocating a marker to point after the inserted text.
@defun set-marker-insertion-type marker type
-@tindex set-marker-insertion-type
This function sets the insertion type of marker @var{marker} to
@var{type}. If @var{type} is @code{t}, @var{marker} will advance when
text is inserted at its position. If @var{type} is @code{nil},
@end defun
@defun marker-insertion-type marker
-@tindex marker-insertion-type
This function reports the current insertion type of @var{marker}.
@end defun
+Most functions that create markers, without an argument allowing to
+specify the insertion type, create them with insertion type
+@code{nil}. Also, the mark has, by default, insertion type
+@code{nil}.
+
@node Moving Markers
@section Moving Marker Positions
@cindex mark ring
One special marker in each buffer is designated @dfn{the mark}. It
-records a position for the user for the sake of commands such as
-@code{kill-region} and @code{indent-rigidly}. Lisp programs should set
-the mark only to values that have a potential use to the user, and never
-for their own internal purposes. For example, the @code{replace-regexp}
-command sets the mark to the value of point before doing any
-replacements, because this enables the user to move back there
-conveniently after the replace is finished.
-
- Many commands are designed so that when called interactively they
-operate on the text between point and the mark. If you are writing such
-a command, don't examine the mark directly; instead, use
+specifies a position to bound a range of text for commands such as
+@code{kill-region} and @code{indent-rigidly}. Lisp programs should
+set the mark only to values that have a potential use to the user, and
+never for their own internal purposes. For example, the
+@code{replace-regexp} command sets the mark to the value of point
+before doing any replacements, because this enables the user to move
+back there conveniently after the replace is finished.
+
+ Many commands are designed to operate on the text between point and
+the mark when called interactively. If you are writing such a
+command, don't examine the mark directly; instead, use
@code{interactive} with the @samp{r} specification. This provides the
values of point and the mark as arguments to the command in an
interactive call, but permits other Lisp programs to specify arguments
maximum number of entries in the mark ring; once the list becomes this
long, adding a new element deletes the last element.
+ There is also a separate global mark ring, but that is used only in a
+few particular user-level commands, and is not relevant to Lisp
+programming. So we do not describe it here.
+
@defun mark &optional force
@cindex current buffer mark
-This function returns the current buffer's mark position as an integer.
-
-If the mark is inactive, @code{mark} normally signals an error.
-However, if @var{force} is non-@code{nil}, then @code{mark} returns the
-mark position anyway---or @code{nil}, if the mark is not yet set for
-this buffer.
+This function returns the current buffer's mark position as an integer,
+or @code{nil} if no mark has ever been set in this buffer.
+
+If Transient Mark mode is enabled, and @code{mark-even-if-inactive} is
+@code{nil}, @code{mark} signals an error if the mark is inactive.
+However, if @var{force} is non-@code{nil}, then @code{mark} disregards
+inactivity of the mark, and returns the mark position anyway (or
+@code{nil}).
@end defun
@defun mark-marker
every buffer-modifying primitive sets @code{deactivate-mark}. The
consequence of this is that commands that modify the buffer normally
make the mark inactive.
+
+Lisp programs can set @code{transient-mark-mode} to @code{only} to
+enable Transient Mark mode for the following command only. During
+that following command, the value of @code{transient-mark-mode} is
+@code{identity}. If it is still @code{identity} at the end of the
+command, it changes to @code{nil}.
@end defopt
@defopt mark-even-if-inactive
Transient Mark mode is enabled). All the primitives that change the
buffer set @code{deactivate-mark}, to deactivate the mark when the
command is finished.
+
+To write Lisp code that modifies the buffer without causing
+deactivation of the mark at the end of the command, bind
+@code{deactivate-mark} to @code{nil} around the code that does the
+modification. For example:
+
+@example
+(let (deactivate-mark)
+ (insert " "))
+@end example
@end defvar
@defun deactivate-mark
@example
@group
mark-ring
-@result{} (#<marker at 11050 in markers.texi>
+@result{} (#<marker at 11050 in markers.texi>
#<marker at 10832 in markers.texi>
@dots{})
@end group
only those functions specifically related to the region itself are
described here.
+The next two functions signal an error if the mark does not point
+anywhere. If Transient Mark mode is enabled and
+@code{mark-even-if-inactive} is @code{nil}, they also signal an error
+if the mark is inactive.
+
@defun region-beginning
This function returns the position of the beginning of the region (as
an integer). This is the position of either point or the mark,
whichever is smaller.
-
-If the mark does not point anywhere, an error is signaled.
@end defun
@defun region-end
This function returns the position of the end of the region (as an
integer). This is the position of either point or the mark, whichever is
larger.
-
-If the mark does not point anywhere, an error is signaled.
@end defun
Few programs need to use the @code{region-beginning} and
to find the beginning and end of the region. This lets other Lisp
programs specify the bounds explicitly as arguments. (@xref{Interactive
Codes}.)
+
+@ignore
+ arch-tag: b1ba2e7a-a0f3-4c5e-875c-7d8e22d73299
+@end ignore