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how to go to old marks. Suggested by Jay Bingham <Jay.Bingham@compaq.com>.
366 lines
15 KiB
Plaintext
366 lines
15 KiB
Plaintext
@c This is part of the Emacs manual.
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@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997 Free Software Foundation, Inc.
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@c See file emacs.texi for copying conditions.
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@node Mark, Killing, Help, Top
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@chapter The Mark and the Region
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@cindex mark
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@cindex setting a mark
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@cindex region
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Many Emacs commands operate on an arbitrary contiguous part of the
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current buffer. To specify the text for such a command to operate on,
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you set @dfn{the mark} at one end of it, and move point to the other
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end. The text between point and the mark is called @dfn{the region}.
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Emacs highlights the region whenever there is one, if you enable
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Transient Mark mode (@pxref{Transient Mark}).
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You can move point or the mark to adjust the boundaries of the region.
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It doesn't matter which one is set first chronologically, or which one
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comes earlier in the text. Once the mark has been set, it remains where
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you put it until you set it again at another place. Each Emacs buffer
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has its own mark, so that when you return to a buffer that had been
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selected previously, it has the same mark it had before.
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Many commands that insert text, such as @kbd{C-y} (@code{yank}) and
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@kbd{M-x insert-buffer}, position point and the mark at opposite ends of
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the inserted text, so that the region contains the text just inserted.
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Aside from delimiting the region, the mark is also useful for
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remembering a spot that you may want to go back to. To make this
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feature more useful, each buffer remembers 16 previous locations of the
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mark in the @dfn{mark ring}.
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@menu
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* Setting Mark:: Commands to set the mark.
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* Transient Mark:: How to make Emacs highlight the region--
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when there is one.
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* Using Region:: Summary of ways to operate on contents of the region.
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* Marking Objects:: Commands to put region around textual units.
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* Mark Ring:: Previous mark positions saved so you can go back there.
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* Global Mark Ring:: Previous mark positions in various buffers.
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@end menu
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@node Setting Mark
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@section Setting the Mark
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Here are some commands for setting the mark:
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@c WideCommands
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@table @kbd
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@item C-@key{SPC}
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Set the mark where point is (@code{set-mark-command}).
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@item C-@@
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The same.
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@item C-x C-x
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Interchange mark and point (@code{exchange-point-and-mark}).
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@item Drag-Mouse-1
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Set point and the mark around the text you drag across.
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@item Mouse-3
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Set the mark where point is, then move point to where you click
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(@code{mouse-save-then-kill}).
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@end table
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For example, suppose you wish to convert part of the buffer to
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upper case, using the @kbd{C-x C-u} (@code{upcase-region}) command,
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which operates on the text in the region. You can first go to the
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beginning of the text to be capitalized, type @kbd{C-@key{SPC}} to put
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the mark there, move to the end, and then type @kbd{C-x C-u}. Or, you
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can set the mark at the end of the text, move to the beginning, and then
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type @kbd{C-x C-u}.
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@kindex C-SPC
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@findex set-mark-command
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The most common way to set the mark is with the @kbd{C-@key{SPC}} command
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(@code{set-mark-command}). This sets the mark where point is. Then you
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can move point away, leaving the mark behind.
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There are two ways to set the mark with the mouse. You can drag mouse
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button one across a range of text; that puts point where you release the
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mouse button, and sets the mark at the other end of that range. Or you
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can click mouse button three, which sets the mark at point (like
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@kbd{C-@key{SPC}}) and then moves point (like @kbd{Mouse-1}). Both of
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these methods copy the region into the kill ring in addition to setting
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the mark; that gives behavior consistent with other window-driven
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applications, but if you don't want to modify the kill ring, you must
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use keyboard commands to set the mark. @xref{Mouse Commands}.
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@kindex C-x C-x
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@findex exchange-point-and-mark
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Ordinary terminals have only one cursor, so there is no way for Emacs
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to show you where the mark is located. You have to remember. The usual
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solution to this problem is to set the mark and then use it soon, before
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you forget where it is. Alternatively, you can see where the mark is
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with the command @kbd{C-x C-x} (@code{exchange-point-and-mark}) which
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puts the mark where point was and point where the mark was. The extent
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of the region is unchanged, but the cursor and point are now at the
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previous position of the mark. In Transient Mark mode, this command
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reactivates the mark.
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@kbd{C-x C-x} is also useful when you are satisfied with the position
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of point but want to move the other end of the region (where the mark
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is); do @kbd{C-x C-x} to put point at that end of the region, and then
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move it. A second use of @kbd{C-x C-x}, if necessary, puts the mark at
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the new position with point back at its original position.
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For more facilities that allow you to go to previously set marks, see
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@ref{Mark Ring}.
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@kindex C-@@
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There is no such character as @kbd{C-@key{SPC}} in ASCII; when you
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type @key{SPC} while holding down @key{CTRL}, what you get on most
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ordinary terminals is the character @kbd{C-@@}. This key is actually
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bound to @code{set-mark-command}. But unless you are unlucky enough to
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have a terminal where typing @kbd{C-@key{SPC}} does not produce
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@kbd{C-@@}, you might as well think of this character as
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@kbd{C-@key{SPC}}. Under X, @kbd{C-@key{SPC}} is actually a distinct
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character, but its binding is still @code{set-mark-command}.
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@node Transient Mark
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@section Transient Mark Mode
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@cindex mode, Transient Mark
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@cindex Transient Mark mode
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@cindex highlighting region
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@cindex region highlighting
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On a terminal that supports colors, Emacs can highlight the current
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region. But normally it does not. Why not?
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Highlighting the region whenever it exists would not be desirable in
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Emacs, because once you have set a mark, there is @emph{always} a
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region (in that buffer). And highlighting the region all the time
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would be a nuisance. So normally Emacs highlights the region only
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immediately after you have selected one with the mouse.
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You can turn on region highlighting by enabling Transient Mark mode.
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This is a more rigid mode of operation in which the region ``lasts''
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only temporarily, so you must set up a region for each command that uses
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one. In Transient Mark mode, most of the time there is no region;
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therefore, highlighting the region when it exists is useful and
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not annoying.
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@findex transient-mark-mode
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To enable Transient Mark mode, type @kbd{M-x transient-mark-mode}.
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This command toggles the mode, so you can repeat the command to turn off
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the mode.
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Here are the details of Transient Mark mode:
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@itemize @bullet
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@item
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To set the mark, type @kbd{C-@key{SPC}} (@code{set-mark-command}).
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This makes the mark active; as you move point, you will see the region
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highlighting grow and shrink.
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@item
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The mouse commands for specifying the mark also make it active. So do
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keyboard commands whose purpose is to specify a region, including
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@kbd{M-@@}, @kbd{C-M-@@}, @kbd{M-h}, @kbd{C-M-h}, @kbd{C-x C-p}, and
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@kbd{C-x h}.
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@item
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When the mark is active, you can execute commands that operate on the
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region, such as killing, indenting, or writing to a file.
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@item
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Any change to the buffer, such as inserting or deleting a character,
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deactivates the mark. This means any subsequent command that operates
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on a region will get an error and refuse to operate. You can make the
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region active again by typing @kbd{C-x C-x}.
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@item
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Commands like @kbd{M->} and @kbd{C-s} that ``leave the mark behind'' in
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addition to some other primary purpose do not activate the new mark.
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You can activate the new region by executing @kbd{C-x C-x}
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(@code{exchange-point-and-mark}).
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@item
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@kbd{C-s} when the mark is active does not alter the mark.
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@item
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Quitting with @kbd{C-g} deactivates the mark.
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@item
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Some commands operate on the region whenever it is active. For
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instance, @kbd{C-x u} in Transient Mark mode operates on the region
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when there is a region. Outside Transient Mark mode, you must type
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@kbd{C-u C-x u} if you want it to operate on the region.
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@xref{Undo}. Other commands that act this way are identified
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in their own documentation.
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@end itemize
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Highlighting of the region uses the @code{region} face; you can
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customize how the region is highlighted by changing this face.
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@xref{Face Customization}.
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@vindex highlight-nonselected-windows
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When multiple windows show the same buffer, they can have different
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regions, because they can have different values of point (though they
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all share one common mark position). Ordinarily, only the selected
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window highlights its region (@pxref{Windows}). However, if the
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variable @code{highlight-nonselected-windows} is non-@code{nil}, then
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each window highlights its own region (provided that Transient Mark mode
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is enabled and the window's buffer's mark is active).
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When Transient Mark mode is not enabled, every command that sets the
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mark also activates it, and nothing ever deactivates it.
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@vindex mark-even-if-inactive
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If the variable @code{mark-even-if-inactive} is non-@code{nil} in
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Transient Mark mode, then commands can use the mark and the region
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even when it is inactive. Region highlighting appears and disappears
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just as it normally does in Transient Mark mode, but the mark doesn't
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really go away when the highlighting disappears.
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@cindex Zmacs mode
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Transient Mark mode is also sometimes known as ``Zmacs mode''
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because the Zmacs editor on the MIT Lisp Machine handled the mark in a
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similar way.
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@node Using Region
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@section Operating on the Region
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@cindex operations on a marked region
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Once you have a region and the mark is active, here are some of the
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ways you can operate on the region:
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@itemize @bullet
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@item
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Kill it with @kbd{C-w} (@pxref{Killing}).
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@item
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Save it in a register with @kbd{C-x r s} (@pxref{Registers}).
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@item
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Save it in a buffer or a file (@pxref{Accumulating Text}).
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@item
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Convert case with @kbd{C-x C-l} or @kbd{C-x C-u} (@pxref{Case}).
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@item
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Indent it with @kbd{C-x @key{TAB}} or @kbd{C-M-\} (@pxref{Indentation}).
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@item
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Fill it as text with @kbd{M-x fill-region} (@pxref{Filling}).
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@item
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Print hardcopy with @kbd{M-x print-region} (@pxref{Hardcopy}).
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@item
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Evaluate it as Lisp code with @kbd{M-x eval-region} (@pxref{Lisp Eval}).
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@end itemize
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Most commands that operate on the text in the
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region have the word @code{region} in their names.
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@node Marking Objects
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@section Commands to Mark Textual Objects
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@cindex marking sections of text
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Here are the commands for placing point and the mark around a textual
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object such as a word, list, paragraph or page.
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@table @kbd
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@item M-@@
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Set mark after end of next word (@code{mark-word}). This command and
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the following one do not move point.
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@item C-M-@@
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Set mark after end of next Lisp expression (@code{mark-sexp}).
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@item M-h
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Put region around current paragraph (@code{mark-paragraph}).
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@item C-M-h
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Put region around current Lisp defun (@code{mark-defun}).
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@item C-x h
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Put region around entire buffer (@code{mark-whole-buffer}).
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@item C-x C-p
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Put region around current page (@code{mark-page}).
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@end table
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@kbd{M-@@} (@code{mark-word}) puts the mark at the end of the next word,
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while @kbd{C-M-@@} (@code{mark-sexp}) puts it at the end of the next Lisp
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expression. These commands handle arguments just like @kbd{M-f} and
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@kbd{C-M-f}.
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@kindex C-x h
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@findex mark-whole-buffer
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Other commands set both point and mark, to delimit an object in the
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buffer. For example, @kbd{M-h} (@code{mark-paragraph}) moves point to
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the beginning of the paragraph that surrounds or follows point, and puts
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the mark at the end of that paragraph (@pxref{Paragraphs}). It prepares
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the region so you can indent, case-convert, or kill a whole paragraph.
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@kbd{C-M-h} (@code{mark-defun}) similarly puts point before and the
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mark after the current or following defun (@pxref{Defuns}). @kbd{C-x
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C-p} (@code{mark-page}) puts point before the current page, and mark at
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the end (@pxref{Pages}). The mark goes after the terminating page
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delimiter (to include it), while point goes after the preceding page
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delimiter (to exclude it). A numeric argument specifies a later page
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(if positive) or an earlier page (if negative) instead of the current
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page.
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Finally, @kbd{C-x h} (@code{mark-whole-buffer}) sets up the entire
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buffer as the region, by putting point at the beginning and the mark at
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the end.
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In Transient Mark mode, all of these commands activate the mark.
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@node Mark Ring
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@section The Mark Ring
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@kindex C-u C-SPC
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@cindex mark ring
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@kindex C-u C-@@
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Aside from delimiting the region, the mark is also useful for
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remembering a spot that you may want to go back to. To make this
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feature more useful, each buffer remembers 16 previous locations of the
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mark, in the @dfn{mark ring}. Commands that set the mark also push the
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old mark onto this ring. To return to a marked location, use @kbd{C-u
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C-@key{SPC}} (or @kbd{C-u C-@@}); this is the command
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@code{set-mark-command} given a numeric argument. It moves point to
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where the mark was, and restores the mark from the ring of former
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marks. Thus, repeated use of this command moves point to all of the old
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marks on the ring, one by one. The mark positions you move through in
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this way are not lost; they go to the end of the ring.
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Each buffer has its own mark ring. All editing commands use the current
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buffer's mark ring. In particular, @kbd{C-u C-@key{SPC}} always stays in
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the same buffer.
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Many commands that can move long distances, such as @kbd{M-<}
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(@code{beginning-of-buffer}), start by setting the mark and saving the
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old mark on the mark ring. This is to make it easier for you to move
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back later. Searches set the mark if they move point. You can tell
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when a command sets the mark because it displays @samp{Mark Set} in the
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echo area.
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If you want to move back to the same place over and over, the mark
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ring may not be convenient enough. If so, you can record the position
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in a register for later retrieval (@pxref{RegPos}).
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@vindex mark-ring-max
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The variable @code{mark-ring-max} specifies the maximum number of
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entries to keep in the mark ring. If that many entries exist and
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another one is pushed, the last one in the list is discarded. Repeating
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@kbd{C-u C-@key{SPC}} cycles through the positions currently in the
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ring.
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@vindex mark-ring
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The variable @code{mark-ring} holds the mark ring itself, as a list of
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marker objects, with the most recent first. This variable is local in
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every buffer.
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@node Global Mark Ring
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@section The Global Mark Ring
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@cindex global mark ring
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In addition to the ordinary mark ring that belongs to each buffer,
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Emacs has a single @dfn{global mark ring}. It records a sequence of
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buffers in which you have recently set the mark, so you can go back
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to those buffers.
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Setting the mark always makes an entry on the current buffer's mark
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ring. If you have switched buffers since the previous mark setting, the
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new mark position makes an entry on the global mark ring also. The
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result is that the global mark ring records a sequence of buffers that
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you have been in, and, for each buffer, a place where you set the mark.
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@kindex C-x C-@key{SPC}
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@findex pop-global-mark
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The command @kbd{C-x C-@key{SPC}} (@code{pop-global-mark}) jumps to
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the buffer and position of the latest entry in the global ring. It also
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rotates the ring, so that successive uses of @kbd{C-x C-@key{SPC}} take
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you to earlier and earlier buffers.
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