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* modes.texi: New node, "Region to Fontify" (for Font Lock).

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This describes font-lock-extend-region-function.
("Other Font Lock Variables"): move "font-lock-lines-before" to
the new node "Region to Fontify".
This commit is contained in:
Alan Mackenzie 2006-03-14 18:30:48 +00:00
parent ef0083218d
commit 2fb936912f
1 changed files with 42 additions and 8 deletions
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50
lispref/modes.texi
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@ -2337,6 +2337,8 @@ Search-based fontification happens second.
* Font Lock Basics:: Overview of customizing Font Lock.
* Search-based Fontification:: Fontification based on regexps.
* Customizing Keywords:: Customizing search-based fontification.
* Region to Fontify:: Controlling which region gets refontified
after a buffer change.
* Other Font Lock Variables:: Additional customization facilities.
* Levels of Font Lock:: Each mode can define alternative levels
so that the user can select more or less.
@ -2717,6 +2719,46 @@ C mode @emph{and} all modes derived from it, do this instead:
font-lock-keyword-face)))))
@end smallexample
@node Region to Fontify
@subsection Region to Fontify after a Buffer Change
When a buffer is changed, the region that Font Lock refontifies is by
default the smallest sequence of whole lines that spans the change.
While this works well most of the time, sometimes it doesn't---for
example, when a buffer change has changed the syntactic meaning of text
on an earlier line.
You can enlarge (or even reduce) the region to fontify by setting either
of the following variables:
@defvar font-lock-lines-before
This variable specifies the number of extra lines to consider when
refontifying the buffer after each text change. Font lock begins
refontifying from that number of lines before the changed region. The
default is 0, but using a larger value can be useful for coping with
multi-line patterns. This variable is ignored whenever
@code{font-lock-extend-region-function} is set and returns a
non-@code{nil} value.
@end defvar
@defvar font-lock-extend-region-function
This buffer-local variable is either @code{nil} or is a function that
determines the region to fontify, which Emacs then calls after each
buffer change.
The function is given three parameters, the standard @var{beg},
@var{end}, and @var{old-len} from after-change-functions (@pxref{Change
Hooks}). It should return either a cons of the beginning and end buffer
positions (in that order) of the region to fontify, or @code{nil} (which
directs the caller to fontify the default region). This function need
not preserve point or the match-data, but must preserve the current
restriction. The region it returns may start or end in the middle of a
line.
Since this function is called after every buffer change, it should be
reasonably fast.
@end defvar
@node Other Font Lock Variables
@subsection Other Font Lock Variables
@ -2772,14 +2814,6 @@ arguments, the beginning and end of the region. The default value is
@code{font-lock-default-unfontify-region}.
@end defvar
@defvar font-lock-lines-before
This variable specifies the number of extra lines to consider when
refontifying the buffer after each text change. Font lock begins
refontifying from that number of lines before the changed region. The
default is 0, but using a larger value can be useful for coping with
multi-line patterns.
@end defvar
@ignore
@defvar font-lock-inhibit-thing-lock
List of Font Lock mode related modes that should not be turned on.