--- Begin Message ---
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Subject: |
font-lock corrupts `end' position in jit-lock after-change function. |
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Date: |
Tue, 5 Jan 2016 21:47:28 +0000 |
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User-agent: |
Mutt/1.5.23 (2014-03-12) |
Hello, Emacs.
With the latest emacs-25 branch (committed 2016-01-05, ~21:15 +0000),
do emacs -Q, and load (or type in) the follow AWK Mode file (M-x
awk-mode, if required):
########################################################################
#!/usr/bin/gawk -f
BEGIN {
x = 4
}
#########################################################################
Notice the fontification of "BEGIN". Type a space anywhere on the first
line. The following happens:
(i) The fontification on the "B" of "BEGIN" is erased instantly.
(ii) Half a second (jit-lock-context-time) later, the fontification on
"EGIN" is erased.
The cause of the problem is in
font-lock-extend-jit-lock-region-after-change. The sequence is as
follows:
(i) In AWK Mode, font-lock-extend-after-change-region-function is
non-nil, and this function is called to set `beg' and `end', the
bounds of the region to fontify. In the above case, this region is
exactly line 1.
(ii) f-l-extend-j-l-r-a-change adds 1 to end. The region (beg end) now
covers line 1 and the "B" at the beginning of line 2.
(iii) After-change fontification fontifies this spurious region, (beg
end). Since "B" is "on its own", it appears to be an ordinary
variable use, hence is fontified without a face.
(iv) Half a second later, context fontification starts from `end', finds
"EGIN" and fontifies this as an ordinary variable, without a face.
The solution I propose is that should the region have been set by
font-lock-extend-after-change-region-function, the `end' position
should be accepted as is.
Here is a patch to implement this. I will commit it soon to emacs-25 if
I hear no objections.
diff --git a/lisp/font-lock.el b/lisp/font-lock.el
index 4a92069..3c1f01d 100644
--- a/lisp/font-lock.el
+++ b/lisp/font-lock.el
@@ -1302,15 +1302,18 @@ font-lock-extend-jit-lock-region-after-change
(point-min))))
(when (< end (point-max))
(setq end
- (if (get-text-property end 'font-lock-multiline)
- (or (text-property-any end (point-max)
- 'font-lock-multiline nil)
- (point-max))
+ (cond
+ ((get-text-property end 'font-lock-multiline)
+ (or (text-property-any end (point-max)
+ 'font-lock-multiline nil)
+ (point-max)))
+ ;; If `end' has been set by the function above, don't corrupt
it.
+ (font-lock-extend-after-change-region-function end)
;; Rounding up to a whole number of lines should include the
;; line right after `end'. Typical case: the first char of
;; the line was deleted. Or a \n was inserted in the middle
;; of a line.
- (1+ end))))
+ (t (1+ end)))))
;; Finally, pre-enlarge the region to a whole number of lines, to try
;; and anticipate what font-lock-default-fontify-region will do, so as to
;; avoid double-redisplay.
--
Alan Mackenzie (Nuremberg, Germany).
--- End Message ---
--- Begin Message ---
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Subject: |
Re: bug#22316: font-lock corrupts `end' position in jit-lock after-change function. |
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Date: |
8 Jan 2016 14:44:05 -0000 |
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User-agent: |
tin/2.3.1-20141224 ("Tallant") (UNIX) (FreeBSD/10.2-RELEASE-p7 (amd64)) |
Bug fixed.
--
Alan Mackenzie (Nuremberg, Germany).
--- End Message ---