* bug#10903: 24.0.93; redisplay glitch with before-string and display overlays
@ 2012-02-27 22:04 Stephen Berman
2012-02-28 20:40 ` Eli Zaretskii
0 siblings, 1 reply; 4+ messages in thread
From: Stephen Berman @ 2012-02-27 22:04 UTC (permalink / raw)
To: 10903
1. emacs -Q
2. Type `C-x b a RET' to get a fresh buffer in Fundamental mode, and at
(point-min) type "012".
3. Type `M-<' so that the cursor is over (i.e. just before) `0'.
4. Type `M-: (overlay-put (make-overlay (point) (point)) 'before-string
"*")'. Now you see this:
*012
5. Type `M-: (overlay-put (make-overlay (point) (1+ (point))) 'display
"")'. Now you see this:
*12
6. Type `M-: (remove-overlays)' to restore "012".
7. Type SPC to advance the cursor and the start of "012" to column one.
8. Repeat step 4. Now you see this:
*012
9. Repeat step 5. Now you see this:
*112
According to my tests, this redisplay glitch happens when the overlays
begin anywhere other than (point-min). It also only happens when the
before-string overlay is added prior to the display string overlay, and
only when the value of the display string is "". I don't know when this
problem appeared, but it does not happen in Emacs 23.3.
In GNU Emacs 24.0.93.1 (i686-suse-linux-gnu, GTK+ Version 2.24.7)
of 2012-02-26 on escher
Windowing system distributor `The X.Org Foundation', version 11.0.11004000
Configured using:
`configure '--without-toolkit-scroll-bars' 'CFLAGS=-g''
Important settings:
value of $LC_ALL: nil
value of $LC_COLLATE: nil
value of $LC_CTYPE: nil
value of $LC_MESSAGES: nil
value of $LC_MONETARY: nil
value of $LC_NUMERIC: nil
value of $LC_TIME: nil
value of $LANG: en_US.UTF-8
value of $XMODIFIERS: @im=local
locale-coding-system: utf-8-unix
default enable-multibyte-characters: t
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#10903: 24.0.93; redisplay glitch with before-string and display overlays
2012-02-27 22:04 bug#10903: 24.0.93; redisplay glitch with before-string and display overlays Stephen Berman
@ 2012-02-28 20:40 ` Eli Zaretskii
2012-02-28 22:25 ` Stephen Berman
0 siblings, 1 reply; 4+ messages in thread
From: Eli Zaretskii @ 2012-02-28 20:40 UTC (permalink / raw)
To: Stephen Berman; +Cc: 10903
> From: Stephen Berman <stephen.berman@gmx.net>
> Date: Mon, 27 Feb 2012 23:04:03 +0100
>
> 1. emacs -Q
>
> 2. Type `C-x b a RET' to get a fresh buffer in Fundamental mode, and at
> (point-min) type "012".
>
> 3. Type `M-<' so that the cursor is over (i.e. just before) `0'.
>
> 4. Type `M-: (overlay-put (make-overlay (point) (point)) 'before-string
> "*")'. Now you see this:
>
> *012
>
> 5. Type `M-: (overlay-put (make-overlay (point) (1+ (point))) 'display
> "")'. Now you see this:
>
> *12
>
> 6. Type `M-: (remove-overlays)' to restore "012".
>
> 7. Type SPC to advance the cursor and the start of "012" to column one.
>
> 8. Repeat step 4. Now you see this:
>
> *012
>
> 9. Repeat step 5. Now you see this:
>
> *112
We were hitting on an old redisplay optimization that didn't play well
with the bidi-aware display engine.
I think I fixed this. Thanks for such a clear-cut test case.
Since Savannah is on the move, I cannot commit the fix, but perhaps
you could test it locally and see if there are any leftovers. Here's
the patch:
=== modified file 'src/xdisp.c'
--- src/xdisp.c 2012-02-12 09:46:33 +0000
+++ src/xdisp.c 2012-02-28 20:35:41 +0000
@@ -5156,6 +5156,10 @@ next_overlay_string (struct it *it)
it->current.overlay_string_index = -1;
it->n_overlay_strings = 0;
it->overlay_strings_charpos = -1;
+ /* If there's an empty display string on the stack, pop the
+ stack, to resync the bidi iterator with IT's position. */
+ if (it->sp > 0 && STRINGP (it->string) && !SCHARS (it->string))
+ pop_it (it);
/* If we're at the end of the buffer, record that we have
processed the overlay strings there already, so that
@@ -5453,8 +5457,15 @@ get_overlay_strings_1 (struct it *it, EM
xassert (!compute_stop_p || it->sp == 0);
/* When called from handle_stop, there might be an empty display
- string loaded. In that case, don't bother saving it. */
- if (!STRINGP (it->string) || SCHARS (it->string))
+ string loaded. In that case, don't bother saving it. But
+ don't use this optimization with the bidi iterator, since we
+ need the corresponding pop_it call to resync the bidi
+ iterator's position with IT's position, after we are done
+ with the overlay strings. (The corresponding call to pop_it
+ in case of an empty display string is in
+ next_overlay_string.) */
+ if (!(!it->bidi_p
+ && STRINGP (it->string) && !SCHARS (it->string)))
push_it (it, NULL);
/* Set up IT to deliver display elements from the first overlay
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#10903: 24.0.93; redisplay glitch with before-string and display overlays
2012-02-28 20:40 ` Eli Zaretskii
@ 2012-02-28 22:25 ` Stephen Berman
2012-02-29 17:52 ` Eli Zaretskii
0 siblings, 1 reply; 4+ messages in thread
From: Stephen Berman @ 2012-02-28 22:25 UTC (permalink / raw)
To: Eli Zaretskii; +Cc: 10903
On Tue, 28 Feb 2012 22:40:17 +0200 Eli Zaretskii <eliz@gnu.org> wrote:
>> From: Stephen Berman <stephen.berman@gmx.net>
>> Date: Mon, 27 Feb 2012 23:04:03 +0100
>>
>> 1. emacs -Q
>>
>> 2. Type `C-x b a RET' to get a fresh buffer in Fundamental mode, and at
>> (point-min) type "012".
>>
>> 3. Type `M-<' so that the cursor is over (i.e. just before) `0'.
>>
>> 4. Type `M-: (overlay-put (make-overlay (point) (point)) 'before-string
>> "*")'. Now you see this:
>>
>> *012
>>
>> 5. Type `M-: (overlay-put (make-overlay (point) (1+ (point))) 'display
>> "")'. Now you see this:
>>
>> *12
>>
>> 6. Type `M-: (remove-overlays)' to restore "012".
>>
>> 7. Type SPC to advance the cursor and the start of "012" to column one.
>>
>> 8. Repeat step 4. Now you see this:
>>
>> *012
>>
>> 9. Repeat step 5. Now you see this:
>>
>> *112
>
> We were hitting on an old redisplay optimization that didn't play well
> with the bidi-aware display engine.
>
> I think I fixed this. Thanks for such a clear-cut test case.
>
> Since Savannah is on the move, I cannot commit the fix, but perhaps
> you could test it locally and see if there are any leftovers. Here's
> the patch:
I applied the patch and rebuilt, and the redisplay glitches I observed
are gone; thanks very much for the quick fix! I consider this bug
resolved, but it should probably be closed after the fix is committed to
the trunk. Thanks again.
Steve Berman
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#10903: 24.0.93; redisplay glitch with before-string and display overlays
2012-02-28 22:25 ` Stephen Berman
@ 2012-02-29 17:52 ` Eli Zaretskii
0 siblings, 0 replies; 4+ messages in thread
From: Eli Zaretskii @ 2012-02-29 17:52 UTC (permalink / raw)
To: Stephen Berman; +Cc: 10903-done
> From: Stephen Berman <stephen.berman@gmx.net>
> Cc: 10903@debbugs.gnu.org
> Date: Tue, 28 Feb 2012 23:25:13 +0100
>
> > Since Savannah is on the move, I cannot commit the fix, but perhaps
> > you could test it locally and see if there are any leftovers. Here's
> > the patch:
>
> I applied the patch and rebuilt, and the redisplay glitches I observed
> are gone; thanks very much for the quick fix! I consider this bug
> resolved, but it should probably be closed after the fix is committed to
> the trunk. Thanks again.
Thanks for testing. I committed the fix (revision 107465 on the
trunk) and closed the bug.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2012-02-27 22:04 bug#10903: 24.0.93; redisplay glitch with before-string and display overlays Stephen Berman
2012-02-28 20:40 ` Eli Zaretskii
2012-02-28 22:25 ` Stephen Berman
2012-02-29 17:52 ` Eli Zaretskii
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