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Each buffer has a special marker, which is designated the mark. When a buffer is newly created, this marker exists but does not point anywhere; this means that the mark doesn’t exist in that buffer yet. Subsequent commands can set the mark.
The mark specifies a position to bound a range of text for
many commands, such as kill-region and
indent-rigidly. These commands typically act on the
text between point and the mark, which is called the
region. If you are writing a command that operates on
the region, don’t examine the mark directly; instead, use
interactive with the ‘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 explicitly. See Interactive
Codes.
Some commands set the mark as a side-effect. Commands should
do this only if it has a potential use to the user, and never for
their own internal purposes. For example, the
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.
Once the mark exists in a buffer, it normally never ceases to
exist. However, it may become inactive, if Transient
Mark mode is enabled. The buffer-local variable
mark-active, if non-nil, means that the
mark is active. A command can call the function
deactivate-mark to deactivate the mark directly, or
it can request deactivation of the mark upon return to the editor
command loop by setting the variable deactivate-mark
to a non-nil value.
If Transient Mark mode is enabled, certain editing commands that normally apply to text near point, apply instead to the region when the mark is active. This is the main motivation for using Transient Mark mode. (Another is that this enables highlighting of the region when the mark is active. See Display.)
In addition to the mark, each buffer has a mark ring
which is a list of markers containing previous values of the
mark. When editing commands change the mark, they should normally
save the old value of the mark on the mark ring. The variable
mark-ring-max specifies the 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.
This function returns the current buffer’s mark
position as an integer, or nil if no mark has
ever been set in this buffer.
If Transient Mark mode is enabled, and
mark-even-if-inactive is nil,
mark signals an error if the mark is inactive.
However, if force is non-nil, then
mark disregards inactivity of the mark, and
returns the mark position (or nil) anyway.
This function returns the marker that represents the current buffer’s mark. It is not a copy, it is the marker used internally. Therefore, changing this marker’s position will directly affect the buffer’s mark. Don’t do that unless that is the effect you want.
(setq m (mark-marker))
⇒ #<marker at 3420 in markers.texi>
(set-marker m 100)
⇒ #<marker at 100 in markers.texi>
(mark-marker)
⇒ #<marker at 100 in markers.texi>
Like any marker, this marker can be set to point at any buffer you like. If you make it point at any buffer other than the one of which it is the mark, it will yield perfectly consistent, but rather odd, results. We recommend that you not do it!
This function sets the mark to position, and activates the mark. The old value of the mark is not pushed onto the mark ring.
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
mark-ring. For this reason, most applications
should use push-mark and pop-mark,
not set-mark.
Novice Emacs Lisp programmers often try to use the mark for the wrong purposes. The mark saves a location for the user’s convenience. An editing command should not alter the mark unless altering the mark is part of the user-level functionality of the command. (And, in that case, this effect should be documented.) To remember a location for internal use in the Lisp program, store it in a Lisp variable. For example:
(let ((beg (point))) (forward-line 1) (delete-region beg (point))).
This function sets the current buffer’s mark to
position, and pushes a copy of the previous mark
onto mark-ring. If position is
nil, then the value of point is used.
The function push-mark normally does
not activate the mark. To do that, specify
t for the argument activate.
A ‘Mark set’ message is displayed
unless nomsg is non-nil.
This function pops off the top element of
mark-ring and makes that mark become the
buffer’s actual mark. This does not move point in the
buffer, and it does nothing if mark-ring is
empty. It deactivates the mark.
This variable, if non-nil, enables Transient
Mark mode. In Transient Mark mode, every buffer-modifying
primitive sets deactivate-mark. As a
consequence, most commands that modify the buffer also
deactivate the mark.
When Transient Mark mode is enabled and the mark is
active, many commands that normally apply to the text near
point instead apply to the region. Such commands should use
the function use-region-p to test whether they
should operate on the region. See The Region.
Lisp programs can set transient-mark-mode to
non-nil, non-t values to enable
Transient Mark mode temporarily. If the value is
lambda, Transient Mark mode is automatically
turned off after any action, such as buffer modification,
that would normally deactivate the mark. If the value is
(only . oldval)
, then transient-mark-mode is set to
the value oldval after any subsequent command that
moves point and is not shift-translated (see shift-translation),
or after any other action that would normally deactivate the
mark.
If this is non-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-nil, deactivation of the mark
turns off region highlighting, but commands that use the mark
behave as if the mark were still active.
If an editor command sets this variable
non-nil, then the editor command loop
deactivates the mark after the command returns (if Transient
Mark mode is enabled). All the primitives that change the
buffer set deactivate-mark, to deactivate the
mark when the command is finished. Setting this variable
makes it buffer-local.
To write Lisp code that modifies the buffer without
causing deactivation of the mark at the end of the command,
bind deactivate-mark to nil around
the code that does the modification. For example:
(let (deactivate-mark) (insert " "))
If Transient Mark mode is enabled or force is
non-nil, this function deactivates the mark and
runs the normal hook deactivate-mark-hook.
Otherwise, it does nothing.
The mark is active when this variable is
non-nil. This variable is always buffer-local in
each buffer. Do not use the value of this variable
to decide whether a command that normally operates on text
near point should operate on the region instead. Use the
function use-region-p for that (see The Region).
These normal hooks are run, respectively, when the mark
becomes active and when it becomes inactive. The hook
activate-mark-hook is also run at the end of the
command loop if the mark is active and it is possible that
the region may have changed.
This function implements the shift-selection behavior of
point-motion commands. See
Shift Selection in The GNU Emacs Manual. It
is called automatically by the Emacs command loop whenever a
command with a ‘^’ character in its
interactive spec is invoked, before the command
itself is executed (see ^).
If shift-select-mode is non-nil
and the current command was invoked via shift translation
(see shift-translation),
this function sets the mark and temporarily activates the
region, unless the region was already temporarily activated
in this way. Otherwise, if the region has been activated
temporarily, it deactivates the mark and restores the
variable transient-mark-mode to its earlier
value.
The value of this buffer-local variable is the list of saved former marks of the current buffer, most recent first.
mark-ring
⇒ (#<marker at 11050 in markers.texi>
#<marker at 10832 in markers.texi>
…)
The value of this variable is the maximum size of
mark-ring. If more marks than this are pushed
onto the mark-ring, push-mark
discards an old mark when it adds a new one.
When Delete Selection mode (see
Delete Selection in The GNU Emacs Manual) is
enabled, commands that operate on the active region (a.k.a.
“selection”) behave slightly differently. This works
by adding the function delete-selection-pre-hook to
the pre-command-hook (see Command Overview).
That function calls delete-selection-helper to
delete the selection as appropriate for the command. If you want
to adapt a command to Delete Selection mode, put the
delete-selection property on the function’s
symbol (see Symbol
Plists); commands that don’t have this property on
their symbol won’t delete the selection. This property can
have one of several values to tailor the behavior to what the
command is supposed to do; see the doc strings of
delete-selection-pre-hook and
delete-selection-helper for the details.
Next: The Region, Previous: Moving Markers, Up: Markers [Contents][Index]