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Clarify that the region is in the Emacs manual

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* doc/emacs/mark.texi (Mark): Try to clarify what's so special
about Emacs' regions (bug#50950).
This commit is contained in:
Lars Ingebrigtsen 2022-09-04 22:58:52 +02:00
parent 1dad2cba15
commit 72ba9efe72
1 changed files with 28 additions and 14 deletions
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42
doc/emacs/mark.texi
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@ -8,26 +8,29 @@
@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; each time you move point, the region
changes.
Emacs, like many other applications, lets you select some arbitrary
part of the buffer text and invoke commands that operate on such
@dfn{selected text}. In Emacs, we call the selected text @dfn{the
region}; its handling is very similar to that of selected text in
other programs, but there are also important differences.
@cindex active region
@cindex activating the mark
Setting the mark at a position in the text also @dfn{activates} it.
When the mark is active, we say also that the region is active; Emacs
The region is the portion of the buffer between @dfn{the mark} and
the current @dfn{point}. You define a region by setting the mark
somewhere (with, for instance, the @kbd{C-SPC} command), and then
moving point to where you want the region to end. (Or you can use the
mouse to define a region.)
The region always extends between point and the mark, no matter
which of them comes earlier in the text; each time you move point, the
region changes.
Setting the mark at a position in the text @dfn{activates} it. When
the mark is active, we say also that the region is active; Emacs
indicates its extent by highlighting the text within it, using the
@code{region} face (@pxref{Face Customization}).
This is one of the few faces that has the @code{:extend t} attribute
by default, which implies that the same face is used to highlight the
text and space between end of line and the window border. To
highlight only the text you could set this attribute to @code{nil}.
@cindex deactivating the mark
After certain non-motion commands, including any command that
changes the text in the buffer, Emacs automatically @dfn{deactivates}
@ -35,6 +38,17 @@ the mark; this turns off the highlighting. You can also explicitly
deactivate the mark at any time, by typing @kbd{C-g}
(@pxref{Quitting}).
Many commands limit what they do to the active region. For
instance, the @kbd{M-%} command (which replaces matching text)
normally works on the entire visible part of the buffer, but if you
have an active region, it'll work on just that region instead.
The mark is useful even if it is not active. For example, you can
move to previous mark locations using the mark ring. @xref{Mark
Ring}. Additionally, some commands will have an effect even on an
inactive region (for example @dfn{upcase-region}). You can also
reactivate the region with commands like @kbd{C-x C-x}.
The above default behavior is known as Transient Mark mode.
Disabling Transient Mark mode switches Emacs to an alternative
behavior, in which the region is usually not highlighted.