@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994 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
* Predicates on Markers:: Testing whether an object is a marker.
* Creating Markers:: Making empty markers or markers at certain places.
* Information from Markers:: Finding the marker's buffer or character position.
-* Changing Markers:: Moving the marker to a new buffer or position.
+* Marker Insertion Types:: Two ways a marker can relocate when you
+ insert where it points.
+* Moving Markers:: Moving the marker to a new buffer or position.
* The Mark:: How ``the mark'' is implemented with a marker.
* The Region:: How to access ``the region''.
@end menu
@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 which 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
characters immediately before and after the deleted text. Inserting
-text at the position of a marker normally leaves the marker in front of
-the new text---unless it is inserted with @code{insert-before-markers}
-(@pxref{Insertion}).
+text at the position of a marker normally leaves the marker either in
+front of or after the new text, depending on the marker's @dfn{insertion
+type} (@pxref{Marker Insertion Types})---unless the insertion is done
+with @code{insert-before-markers} (@pxref{Insertion}).
@cindex marker garbage collection
Insertion and deletion in a buffer must check all the markers and
@end defun
@defun number-or-marker-p object
-This function returns @code{t} if @var{object} is a number (either kind)
-or a marker, @code{nil} otherwise.
+This function returns @code{t} if @var{object} is a number (either
+integer or floating point) or a marker, @code{nil} otherwise.
@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 functions returns a newly allocated marker that does not point
+This function returns a newly created marker that does not point
anywhere.
@example
@end example
@end defun
-@defun copy-marker marker-or-integer
+@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,
@code{copy-marker} returns a new marker that points to position
@var{marker-or-integer} in the current buffer.
+The new marker's insertion type is specified by the argument
+@var{insertion-type}. @xref{Marker Insertion Types}.
+
If passed an integer argument less than 1, @code{copy-marker} returns a
new marker that points to the beginning of the current buffer. If
passed an integer argument greater than the length of the buffer,
@code{copy-marker} returns a new marker that points to the end of the
buffer.
+@example
+@group
+(copy-marker 0)
+ @result{} #<marker at 1 in markers.texi>
+@end group
+
+@group
+(copy-marker 20000)
+ @result{} #<marker at 7572 in markers.texi>
+@end group
+@end example
+
An error is signaled if @var{marker} is neither a marker nor an
integer.
+@end defun
+
+ Two distinct markers are considered @code{equal} (even though not
+@code{eq}) to each other if they have the same position and buffer, or
+if they both point nowhere.
@example
@group
(equal p q)
@result{} t
@end group
-
-@group
-(copy-marker 0)
- @result{} #<marker at 1 in markers.texi>
-@end group
-
-@group
-(copy-marker 20000)
- @result{} #<marker at 7572 in markers.texi>
-@end group
@end example
-@end defun
@node Information from Markers
@section Information from Markers
@end example
@end defun
- Two distinct markers are considered @code{equal} (even though not
-@code{eq}) to each other if they have the same position and buffer, or
-if they both point nowhere.
+@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 Changing Markers
-@section Changing Marker Positions
+@node Marker Insertion Types
+@section Marker Insertion Types
+
+@cindex insertion type of a marker
+ When you insert text directly at the place where a marker points,
+there are two possible ways to relocate that marker: it can point before
+the inserted text, or point after it. You can specify which one a given
+marker should do by setting its @dfn{insertion type}. Note that use of
+@code{insert-before-markers} ignores markers' insertion types, always
+relocating a marker to point after the inserted text.
+
+@defun set-marker-insertion-type marker 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},
+@var{marker} does not advance when text is inserted there.
+@end defun
+
+@defun marker-insertion-type marker
+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
This section describes how to change the position of an existing
marker. When you do this, be sure you know whether the marker is used
the current buffer.
If @var{position} is less than 1, @code{set-marker} moves @var{marker}
-to the beginning of the buffer. If the value of @var{position} is
-greater than the size of the buffer, @code{set-marker} moves marker to
-the end of the buffer. If @var{position} is @code{nil} or a marker that
-points nowhere, then @var{marker} is set to point nowhere.
+to the beginning of the buffer. If @var{position} is greater than the
+size of the buffer, @code{set-marker} moves marker to the end of the
+buffer. If @var{position} is @code{nil} or a marker that points
+nowhere, then @var{marker} is set to point nowhere.
The value returned is @var{marker}.
@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
-@kbd{C-w} and @kbd{C-x @key{TAB}}. 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
Each buffer has its own value of the mark that is independent of the
value of the mark in other buffers. When a buffer is created, the mark
exists but does not point anywhere. We consider this state as ``the
-absence of a mark in that buffer''.
+absence of a mark in that buffer.''
Once the mark ``exists'' in a buffer, it normally never ceases to
exist. However, it may become @dfn{inactive}, if Transient Mark mode is
-enabled. The variable @code{mark-active}, which is always local in all
-buffers, indicates whether the mark is active: non-@code{nil} means
-yes. A command can request deactivation of the mark upon return to the
-editor command loop by setting @code{deactivate-mark} to a
-non-@code{nil} value (but this deactivation only follows if Transient
+enabled. The variable @code{mark-active}, which is always buffer-local
+in all buffers, indicates whether the mark is active: non-@code{nil}
+means yes. A command can request deactivation of the mark upon return
+to the editor command loop by setting @code{deactivate-mark} to a
+non-@code{nil} value (but this causes deactivation only if Transient
Mark mode is enabled).
The main motivation for using Transient Mark mode is that this mode
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
This function returns the current buffer's mark. This is the very marker
-which records the mark location inside Emacs, not a copy. Therefore,
+that records the mark location inside Emacs, not a copy. Therefore,
changing this marker's position will directly affect the position of the mark.
Don't do it unless that is the effect you want.
This function sets the mark to @var{position}, and activates the mark.
The old value of the mark is @emph{not} pushed onto the mark ring.
-@strong{Please note:} use this function only if you want the user to
+@strong{Please note:} Use this function only if you want the user to
see that the mark has moved, and you want the previous mark position to
be lost. Normally, when a new mark is set, the old one should go on the
@code{mark-ring}. For this reason, most applications should use
@defopt transient-mark-mode
@cindex Transient Mark mode
-This variable enables Transient Mark mode, in which every
-buffer-modifying primitive sets @code{deactivate-mark}. The consequence
-of this is that commands that modify the buffer normally make the mark
-inactive.
+This variable if non-@code{nil} enables Transient Mark mode, in which
+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
+If this is non-@code{nil}, Lisp programs and the Emacs user can use the
+mark even when it is inactive. This option affects the behavior of
+Transient Mark mode. When the option is non-@code{nil}, deactivation of
+the mark turns off region highlighting, but commands that use the mark
+behave as if the mark were still active.
@end defopt
@defvar deactivate-mark
If an editor command sets this variable non-@code{nil}, then the editor
-command loop deactivates the mark after the command returns.
+command loop deactivates the mark after the command returns (if
+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
+This function deactivates the mark, if Transient Mark mode is enabled.
+Otherwise it does nothing.
+@end defun
+
@defvar mark-active
The mark is active when this variable is non-@code{nil}. This variable
-is always local in each buffer.
+is always buffer-local in each buffer.
@end defvar
@defvar activate-mark-hook
@defvarx deactivate-mark-hook
These normal hooks are run, respectively, when the mark becomes active
-and when it becomes inactive. The hook @code{activate-mark-hook} is also
-run at the end of a command if the mark is active and the region may
-have changed.
+and when it becomes inactive. The hook @code{activate-mark-hook} is
+also run at the end of a command if the mark is active and it is
+possible that the region may have changed.
@end defvar
@defvar mark-ring
@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