Merge from emacs--rel--22

[gnu-emacs] / doc / emacs / mark.texi

@c This is part of the Emacs manual.
@c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2001, 2002,
@c   2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Mark, Killing, Help, Top
@chapter The Mark and the Region
@cindex mark
@cindex setting a mark
@cindex region

  Many Emacs commands operate on an arbitrary contiguous part of the
current buffer.  To specify the text for such a command to operate on,
you set @dfn{the mark} at one end of it, and move point to the other
end.  The text between point and the mark is called @dfn{the region}.

  The region always extends between point and the mark, no matter
which one comes earlier in the text---the region starts from point or
the mark (whichever comes first), and ends at point or the mark
(whichever comes last).  Every time you move point, the region
changes.  When a region is active, Emacs highlights it using the
@code{region} face.  You can customize the appearance of the
highlighting by changing this face (@pxref{Face Customization}).

  The region persists only until you use it.  The mark is
automatically @dfn{deactivated} after certain non-motion commands,
including any command that changes the text in the buffer.  You can
also explicitly deactivate the mark at any time, by typing @kbd{C-g}
(@pxref{Quitting}).

@vindex highlight-nonselected-windows
  Each Emacs buffer has its own mark, and setting the mark in one
buffer has no effect on other buffers' marks.  When you return to a
buffer with an active mark, the mark is at the same place as before.
When multiple windows show the same buffer, they can have different
values of point, and thus different regions (though they all share one
common mark position).  @xref{Windows}.  Ordinarily, only the selected
window highlights its region, if a region exists; however, if the
variable @code{highlight-nonselected-windows} is non-@code{nil}, each
window highlights its own region.

  If Delete Selection mode is enabled, some commands delete the region
when used while the mark is active.  @xref{Mouse Commands}.

@menu
* Setting Mark::        Commands to set the mark.
* Marking Objects::     Commands to put region around textual units.
* Using Region::        Summary of ways to operate on contents of the region.
* Persistent Mark::     Keeping the mark active all the time.
* Mark Ring::           Previous mark positions saved so you can go back there.
* Global Mark Ring::    Previous mark positions in various buffers.
@end menu

@node Setting Mark
@section Setting the Mark

  Here are some commands for setting the mark:

@table @kbd
@item C-@key{SPC}
Set the mark where point is (@code{set-mark-command}).
@item C-@@
The same.
@item C-x C-x
Set the mark where point was, and move point where the mark was
(@code{exchange-point-and-mark}).
@item Drag-Mouse-1
Set point and the mark around the text you drag across.
@item Mouse-3
Set the mark where point is, then move point to where you click
(@code{mouse-save-then-kill}).
@end table

@kindex C-SPC
@findex set-mark-command
  The most common way to set the mark is with @kbd{C-@key{SPC}}
(@code{set-mark-command}).  This sets the mark where point is.  You
can then move point away, leaving the mark behind.

  For example, suppose you wish to convert part of the buffer to upper
case.  To accomplish this, first go to the beginning of the text to be
capitalized, type @kbd{C-@key{SPC}}, and move point until the desired
portion of text is highlighted.  You can now type @kbd{C-x C-u}
(@code{upcase-region}), which converts the text in the region to upper
case.  This also automatically deactivates the mark.  (Alternatively,
you could set the mark at the end, move to the beginning, and do
@kbd{C-x C-u}.)

@kindex C-x C-x
@findex exchange-point-and-mark
  The command @kbd{C-x C-x} (@code{exchange-point-and-mark}) puts the
mark where point was and moves point where the mark was, keeping the
region unchanged.  If no mark is active, Emacs reactivates the mark at
the position where it was last set.  @kbd{C-x C-x} is useful when you
are satisfied with the position of point but want to move the other
end of the region (where the mark is); do @kbd{C-x C-x} to put point
at that end of the region, and then move it.  Using @kbd{C-x C-x} a
second time, if necessary, puts the mark at the new position with
point back at its original position.

  You can also set the mark with the mouse.  In fact, there are two
ways to do this.  You can press the left mouse button
(@kbd{down-mouse-1}) and drag the mouse across a range of text while
holding down the button; this sets the mark where you first pressed
the mouse button, and point where you release it.  Alternatively, you
can click the right mouse button (@kbd{mouse-3}), which sets the mark
at point and then moves point to where you clicked.

  Using the mouse to mark a region also copies the region into the
kill ring (@pxref{Kill Ring}).  If you don't want to modify the kill
ring, you must use keyboard commands to set the mark.  @xref{Mouse
Commands}.

@kindex C-@@
  There is no such character as @kbd{C-@key{SPC}} in @acronym{ASCII};
when you type @key{SPC} while holding down @key{CTRL} on a text
terminal, what you get is the character @kbd{C-@@}.  This key is also
bound to @code{set-mark-command}---so unless you are unlucky enough to
have a text terminal where typing @kbd{C-@key{SPC}} does not produce
@kbd{C-@@}, you might as well think of this character as
@kbd{C-@key{SPC}}.

  Whenever the mark is active, you can deactivate it by typing
@kbd{C-g} (@pxref{Quitting}).  The mark is also automatically
deactivated after certain non-motion commands.

@node Marking Objects
@section Commands to Mark Textual Objects

@cindex marking sections of text
  Here are the commands for placing point and the mark around a textual
object such as a word, list, paragraph or page:

@table @kbd
@item M-@@
Set mark after end of next word (@code{mark-word}).  This command and
the following one do not move point.
@item C-M-@@
Set mark after end of following balanced expression (@code{mark-sexp}).
@item M-h
Move point to the beginning of the current paragraph, and set mark at
the end (@code{mark-paragraph}).
@item C-M-h
Move point to the beginning of the current defun, and set mark at the
end (@code{mark-defun}).
@item C-x h
Move point to the beginning of the buffer, and set mark at the end
(@code{mark-whole-buffer}).
@item C-x C-p
Move point to the beginning of the current page, and set mark at the
end (@code{mark-page}).
@end table

@kbd{M-@@} (@code{mark-word}) puts the mark at the end of the next
word, while @kbd{C-M-@@} (@code{mark-sexp}) puts it at the end of the
next balanced expression (@pxref{Expressions}).  These commands handle
arguments just like @kbd{M-f} and @kbd{C-M-f}.

@kindex C-x h
@findex mark-whole-buffer
   Other commands set both point and mark, to delimit an object in the
buffer.  For example, @kbd{M-h} (@code{mark-paragraph}) moves point to
the beginning of the paragraph that surrounds or follows point, and
puts the mark at the end of that paragraph (@pxref{Paragraphs}).  It
prepares the region so you can indent, case-convert, or kill a whole
paragraph.  With a prefix argument, if the argument's value is positive,
@kbd{M-h} marks that many paragraphs starting with the one surrounding
point.  If the prefix argument is @minus{}@var{n}, @kbd{M-h} also
marks @var{n} paragraphs, running back form the one surrounding point.
In that last case, point moves forward to the end of that paragraph,
and the mark goes at the start of the region.

  @kbd{C-M-h} (@code{mark-defun}) similarly puts point before, and the
mark after, the current (or following) major top-level definition, or
defun (@pxref{Moving by Defuns}).  Repeating @kbd{C-M-h} extends
the region to subsequent defuns.

  @kbd{C-x C-p} (@code{mark-page}) puts point before the current page,
and mark at the end (@pxref{Pages}).  The mark goes after the
terminating page delimiter (to include it in the region), while point
goes after the preceding page delimiter (to exclude it).  A numeric
argument specifies a later page (if positive) or an earlier page (if
negative) instead of the current page.

  While the mark is active, repeating the above commands extends the
region accordingly.  For example, you can type either @kbd{C-u 2 M-@@}
or @kbd{M-@@ M-@@} to mark the next two words.  Similarly, repeating
the @kbd{M-h} command extends the region to subsequent paragraphs.

  Finally, @kbd{C-x h} (@code{mark-whole-buffer}) sets up the entire
buffer as the region, by putting point at the beginning and the mark at
the end.  (In some programs this is called ``select all.'')

@node Using Region
@section Operating on the Region

@cindex operations on a marked region
  Once you have a region, here are some of the ways you can operate on
it:

@itemize @bullet
@item
Kill it with @kbd{C-w} (@pxref{Killing}).
@item
Copy it to the kill ring with @kbd{M-w} (@pxref{Yanking}).
@item
Convert case with @kbd{C-x C-l} or @kbd{C-x C-u} (@pxref{Case}).
@item
Undo changes within it using @kbd{C-u C-/} (@pxref{Undo}).
@item
Replace text within it using @kbd{M-%} (@pxref{Query Replace}).
@item
Indent it with @kbd{C-x @key{TAB}} or @kbd{C-M-\} (@pxref{Indentation}).
@item
Fill it as text with @kbd{M-x fill-region} (@pxref{Filling}).
@item
Print hardcopy with @kbd{M-x print-region} (@pxref{Printing}).
@item
Evaluate it as Lisp code with @kbd{M-x eval-region} (@pxref{Lisp Eval}).
@item
Save it in a register with @kbd{C-x r s} (@pxref{Registers}).
@item
Save it in a buffer or a file (@pxref{Accumulating Text}).
@end itemize

  Most commands that operate on the text in the region have the word
@code{region} in their names.

@node Persistent Mark
@section Persistent Marks
@cindex mode, Transient Mark
@cindex Transient Mark mode
@cindex highlighting region
@cindex region highlighting
@cindex Zmacs mode

  By default, the region is highlighted whenever it exists, and it
disappears once you use it or explicitly deactivate the mark.  This
behavior is called Transient Mark mode@footnote{It is also sometimes
called @dfn{Zmacs mode}, because the Zmacs editor on the MIT Lisp
Machine handled the mark in a similar way.}.

@findex transient-mark-mode
  Turning off Transient Mark mode switches Emacs to an alternative
mode of operation, which was the default prior to Emacs 23.  When
Transient Mark mode is off, the mark is persistent: it is @emph{never}
deactivated, but can be set to different locations using commands such
as @kbd{C-@key{SPC}}.  After the first time you set the mark in a
buffer, there is always a region in that buffer.  Emacs will not
highlight the region, because that would be a nuisance.  As an
exception, the region is temporarily highlighted after it is set with
the mouse.

  To turn off Transient Mark mode, type @kbd{M-x transient-mark-mode}.
This command toggles the mode; you can use the same command to turn
Transient Mark mode on again.  You can also toggle Transient Mark mode
using the menu bar: in the @samp{Options} menu, use the @samp{Active
Region Highlighting} menu item.

  Here are the details of how Emacs behaves when Transient Mark mode
is off:

@itemize @bullet
@item
Emacs does not show where the mark is located---you have to remember.
The usual solution to this problem is to set the mark and then use it
soon, before you forget where it is.  Alternatively, you can check the
location of the mark by using @kbd{C-x C-x}, which exchanges the
positions of the point and the mark (@pxref{Setting Mark}).

@item
Many commands that insert text, such as @kbd{C-y} (@code{yank}),
position point and the mark at opposite ends of the inserted text, so
that the region consists of the text just inserted.  You can tell when
a command sets the mark because it displays @samp{Mark set} in the
echo area.

@item
Many commands that move point long distances, like @kbd{M-<} and
@kbd{C-s}, first set the mark where point was.

@item
Some commands that ordinarily operate on the region, if one exists,
act instead on the entire buffer.  For instance, @kbd{C-x u} normally
reverses changes within the region if one exists; when Transient Mark
mode is off, it acts on the entire buffer.  However, you can type
@kbd{C-u C-x u} to make it operate on the region.  @xref{Undo}.  Other
commands that act this way are identified in their own documentation.
@end itemize

  While Transient Mark mode is off, you can activate it temporarily
using @kbd{C-@key{SPC} C-@key{SPC}} or @kbd{C-u C-x C-x}.

@table @kbd
@item C-@key{SPC} C-@key{SPC}
@kindex C-@key{SPC} C-@key{SPC}
Set the mark at point (like plain @kbd{C-@key{SPC}}) and enable
Transient Mark mode just once, until the mark is deactivated.  (This
is not really a separate command; you are using the @kbd{C-@key{SPC}}
command twice.)

@item C-u C-x C-x
@kindex C-u C-x C-x
Activate the mark without changing it; enable Transient Mark mode just
once, until the mark is deactivated.  (This is the @kbd{C-x C-x}
command, @code{exchange-point-and-mark}, with a prefix argument.)
@end table

  These commands set or activate the mark, and enable Transient Mark
mode only until the mark is deactivated.  One reason you may want to
use them is that some commands operate on the entire buffer instead of
the region when Transient Mark mode is off.  Enabling Transient Mark
mode momentarily gives you a way to use these commands on the region.

@node Mark Ring
@section The Mark Ring

@cindex mark ring
  Aside from delimiting the region, the mark is also useful for
remembering spots that you may want to go back to.  Each buffer
remembers 16 previous locations of the mark, in the @dfn{mark ring}.
Commands that set the mark also push the old mark onto this ring.

@table @kbd
@item C-@key{SPC} C-@key{SPC}
Set the mark, pushing it onto the mark ring, without activating it.
@item C-u C-@key{SPC}
Move point to where the mark was, and restore the mark from the ring
of former marks.
@end table

@kindex C-SPC C-SPC
  The command C-@key{SPC} C-@key{SPC} is handy when you want to use
the mark to remember a position to which you may want to return.  It
pushes the current point onto the mark ring, without activating the
mark (which would cause Emacs to highlight the region).  This is
actually two consecutive invocations of @kbd{C-@key{SPC}}
(@code{set-mark-command}); the first @kbd{C-@key{SPC}} sets the mark,
and the second @kbd{C-@key{SPC}} deactivates it.  (When Transient Mark
mode is off, C-@key{SPC} C-@key{SPC} instead activates Transient Mark
mode temporarily.  @xref{Persistent Mark}.)

@kindex C-u C-SPC
  To return to a marked position, use @code{set-mark-command} with a
prefix argument: @kbd{C-u C-@key{SPC}}.  This moves point to where the
mark was, and deactivates the mark if it was active.  Each subsequent
@kbd{C-u C-@key{SPC}} jumps to a prior position stored in the mark
ring.  The positions you move through in this way are not lost; they
go to the end of the ring.

@vindex set-mark-command-repeat-pop
  If you set @code{set-mark-command-repeat-pop} to non-@code{nil},
then immediately after you type @kbd{C-u C-@key{SPC}}, you can type
@kbd{C-@key{SPC}} instead of @kbd{C-u C-@key{SPC}} to cycle through
the mark ring.  By default, @code{set-mark-command-repeat-pop} is
@code{nil}.

  Each buffer has its own mark ring.  All editing commands use the
current buffer's mark ring.  In particular, @kbd{C-u C-@key{SPC}}
always stays in the same buffer.

@vindex mark-ring-max
  The variable @code{mark-ring-max} specifies the maximum number of
entries to keep in the mark ring.  If that many entries exist and
another one is pushed, the earliest one in the list is discarded.  Repeating
@kbd{C-u C-@key{SPC}} cycles through the positions currently in the
ring.

@vindex mark-even-if-inactive
  If the variable @code{mark-even-if-inactive} is @code{nil}, commands
can only use the mark and the region when it is active.  This variable
is non-@code{nil} by default.

  If you want to move back to the same place over and over, the mark
ring may not be convenient enough.  If so, you can record the position
in a register for later retrieval (@pxref{RegPos,, Saving Positions in
Registers}).

@node Global Mark Ring
@section The Global Mark Ring
@cindex global mark ring

  In addition to the ordinary mark ring that belongs to each buffer,
Emacs has a single @dfn{global mark ring}.  It records a sequence of
buffers in which you have recently set the mark, so you can go back
to those buffers.

  Setting the mark always makes an entry on the current buffer's mark
ring.  If you have switched buffers since the previous mark setting, the
new mark position makes an entry on the global mark ring also.  The
result is that the global mark ring records a sequence of buffers that
you have been in, and, for each buffer, a place where you set the mark.

@kindex C-x C-@key{SPC}
@findex pop-global-mark
  The command @kbd{C-x C-@key{SPC}} (@code{pop-global-mark}) jumps to
the buffer and position of the latest entry in the global ring.  It also
rotates the ring, so that successive uses of @kbd{C-x C-@key{SPC}} take
you to earlier and earlier buffers.

@ignore
   arch-tag: f35e4d82-911b-4cfc-a3d7-3c87b2abba20
@end ignore