Display updates strangely - extra text appears and then disappears

Display updates strangely - extra text appears and then disappears

[Adam Sjøgren]

After this commit ('git bisect' tells me):

  commit 8275687bb908174b84021ee15ecd959733cecb9d
  Author: Eli Zaretskii <eliz@gnu.org>
  Date:   Sat Mar 25 16:59:17 2017 +0300

      Fix a segfault due to failure to realize some faces

      * src/xdisp.c (redisplay_internal): If the frame becomes garbaged
      while redisplaying its windows, redisplay all of its windows
      again.  (Bug#26097)
      (init_iterator): When freeing all realized faces on all frames,
      reset the 'face_change' flag of the frame whose window we are
      about to iterate.

the *Group* buffer in Gnus has extra text where there should be none
when you quit a summer and return. After 0.5-1 seconds the extra text
disappears and the buffer looks normal again.

It also happens sometimes when switching to another virtual desktop and
then back to the desktop with Emacs on it.

Video of the effect:

 · https://koldfront.dk/misc/gnu-emacs/redisplay.ogg (8.7 MB)


  Best regards,

    Adam

-- 
 "Money always takes the place of life"                       Adam Sjøgren
                                                         asjo@koldfront.dk

Re: Display updates strangely - extra text appears and then disappears

[Eli Zaretskii]

> From: asjo@koldfront.dk (Adam Sjøgren)
> Date: Sun, 26 Mar 2017 16:37:03 +0200
> 
> After this commit ('git bisect' tells me):
> 
>   commit 8275687bb908174b84021ee15ecd959733cecb9d
>   Author: Eli Zaretskii <eliz@gnu.org>
>   Date:   Sat Mar 25 16:59:17 2017 +0300
> 
>       Fix a segfault due to failure to realize some faces
> 
>       * src/xdisp.c (redisplay_internal): If the frame becomes garbaged
>       while redisplaying its windows, redisplay all of its windows
>       again.  (Bug#26097)
>       (init_iterator): When freeing all realized faces on all frames,
>       reset the 'face_change' flag of the frame whose window we are
>       about to iterate.
> 
> the *Group* buffer in Gnus has extra text where there should be none
> when you quit a summer and return. After 0.5-1 seconds the extra text
> disappears and the buffer looks normal again.

Thanks.  Can you provide a recipe starting from "emacs -Q" to
reproduce the problem?  Preferably without virtual desktops.

Re: Display updates strangely - extra text appears and then disappears

[Adam Sjøgren]

Eli writes:

> Thanks.  Can you provide a recipe starting from "emacs -Q" to
> reproduce the problem?  Preferably without virtual desktops.

Yes.

After starting "emacs -Q", evaluate:

  (setq gnus-select-method '(nntp "feedbase.org"
                                  (nntp-open-connection-function nntp-open-tls-stream)
                                  (nntp-port-number 563)
                                  (nntp-address "feedbase.org")))

Then do M-x gnus, and enter the server buffer by pressing '^'.

Enter the server browse buffer for feedbase org by pressing 'RET' with
point on its line. Subscribe to, at least, 20 groups (pressing 'u' with
point on each line).

Exit the server browse buffer by pressing 'q' and exit the server buffer
by pressing 'q'. You are in the group buffer now, showing the 20 groups
you subscribed to.

Enter a group by pressing 'RET' with point on it. Open the first article
by pressing 'RET'. The display of the summary (top) buffer is messed up.

Exit the group by pressing 'q'. The group buffer is now messed up:

 · https://koldfront.dk/misc/gnu-emacs/redisplay-q-gnus.png

If you press 'g' (to check for new articles), the group buffer is
updated and displays correctly:

 · https://koldfront.dk/misc/gnu-emacs/redisplay-q-gnus-g.png


  Best regards,

    Adam

-- 
 "Oh, we all like motorcycles, to some degree."               Adam Sjøgren
                                                         asjo@koldfront.dk

Re: Display updates strangely - extra text appears and then disappears

[Noam Postavsky]

On Sun, Mar 26, 2017 at 11:57 AM, Adam Sjøgren <asjo@koldfront.dk> wrote:
>
> Exit the group by pressing 'q'. The group buffer is now messed up:
>
>  · https://koldfront.dk/misc/gnu-emacs/redisplay-q-gnus.png
>
> If you press 'g' (to check for new articles), the group buffer is
> updated and displays correctly:
>
>  · https://koldfront.dk/misc/gnu-emacs/redisplay-q-gnus-g.png
>

I guess this is the same problem as what Tino reported:
https://lists.gnu.org/archive/html/emacs-devel/2017-03/msg00688.html

I can't reproduce by following either recipe here (GNU/Linux, both GTK
and Lucid). It probably depends on the fonts installed.

Re: Display updates strangely - extra text appears and then disappears

[Eli Zaretskii]

> From: asjo@koldfront.dk (Adam Sjøgren)
> Date: Sun, 26 Mar 2017 17:57:52 +0200
> 
> Eli writes:
> 
> > Thanks.  Can you provide a recipe starting from "emacs -Q" to
> > reproduce the problem?  Preferably without virtual desktops.
> 
> Yes.

Thanks.  I followed the recipe, but my display is not messed up as you
describe.

Could you perhaps try the recipe after disabling double-buffering,
like this:

  M-: (modify-frame-parameters nil '((inhibit-double-buffering . t))) RET

If you repeat the recipe after evaluating the above, does the problem
still appear?

Re: Display updates strangely - extra text appears and then disappears

[Adam Sjøgren]

Eli writes:

> Thanks.  I followed the recipe, but my display is not messed up as you
> describe.

I guess our environments differs in some aspect. Is there anything I
should check?

> Could you perhaps try the recipe after disabling double-buffering,
> like this:
>
>   M-: (modify-frame-parameters nil '((inhibit-double-buffering . t))) RET
>
> If you repeat the recipe after evaluating the above, does the problem
> still appear?

The problem still appears after doing that.

I just noticed that C-l also cleans up the display (perhaps not that
surprising).

I just found a simpler recipe to reproduce the problem:

 * Start emacs -Q
 * Split the window in two: C-x 2
 * Unsplit it: C-x 1

The text in the *scratch* buffer is repeated after where the line should
end:

 · https://koldfront.dk/misc/gnu-emacs/redisplay-simple.png

and it stays that way until I do something, like editing the buffer or
pressing C-l, for instance. Both with and without double buffering.


  Best regards,

    Adam

-- 
 "This Interweb thing, it might just catch on, I'm            Adam Sjøgren
  telling you."                                          asjo@koldfront.dk

Re: Display updates strangely - extra text appears and then disappears

[Eli Zaretskii]

> From: asjo@koldfront.dk (Adam Sjøgren)
> Date: Sun, 26 Mar 2017 18:54:51 +0200
> 
> Eli writes:
> 
> > Thanks.  I followed the recipe, but my display is not messed up as you
> > describe.
> 
> I guess our environments differs in some aspect. Is there anything I
> should check?

I have no idea what could be responsible for the differences in
behavior.

> > Could you perhaps try the recipe after disabling double-buffering,
> > like this:
> >
> >   M-: (modify-frame-parameters nil '((inhibit-double-buffering . t))) RET
> >
> > If you repeat the recipe after evaluating the above, does the problem
> > still appear?
> 
> The problem still appears after doing that.

OK.

> I just found a simpler recipe to reproduce the problem:
> 
>  * Start emacs -Q
>  * Split the window in two: C-x 2
>  * Unsplit it: C-x 1
> 
> The text in the *scratch* buffer is repeated after where the line should
> end:
> 
>  · https://koldfront.dk/misc/gnu-emacs/redisplay-simple.png

Doesn't happen here, either.

I need to test an alternative solution for the bug whose fix seems to
be causing this.

Re: Display updates strangely - extra text appears and then disappears

[Eli Zaretskii]

Can you try the patch below, please?

diff --git a/src/xdisp.c b/src/xdisp.c
index 3255052..b04f5f1 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -14139,8 +14139,6 @@ redisplay_internal (void)
 		     winds up calling adjust_frame_glyphs, for example. */
 		  if (!f_garbaged_flag && FRAME_GARBAGED_P (f))
 		    {
-		      f->garbaged = false;
-		      fset_redisplay (f);
 		      goto retry_frame;
 		    }
 

Re: Display updates strangely - extra text appears and then disappears

[Adam Sjøgren]

Eli writes:

> Can you try the patch below, please?
>
> diff --git a/src/xdisp.c b/src/xdisp.c
> index 3255052..b04f5f1 100644
> --- a/src/xdisp.c
> +++ b/src/xdisp.c
> @@ -14139,8 +14139,6 @@ redisplay_internal (void)
>  		     winds up calling adjust_frame_glyphs, for example. */
>  		  if (!f_garbaged_flag && FRAME_GARBAGED_P (f))
>  		    {
> -		      f->garbaged = false;
> -		      fset_redisplay (f);
>  		      goto retry_frame;
>  		    }

Applying this patch makes the problem go away for me (both in -Q and in
my regular setup).


  Thanks!

    Adam

-- 
 "Jabba the Hutt meets Rudolf the Reindeer. I                 Adam Sjøgren
  dunno, Mom."                                           asjo@koldfront.dk

Re: Display updates strangely - extra text appears and then disappears

[Eli Zaretskii]

> From: asjo@koldfront.dk (Adam Sjøgren)
> Date: Sun, 26 Mar 2017 19:50:20 +0200
> 
> Applying this patch makes the problem go away for me (both in -Q and in
> my regular setup).

Thanks.  Now I just have to make sure this still fixes the original
bug...

Re: Display updates strangely - extra text appears and then disappears

[Eli Zaretskii]

> Date: Sun, 26 Mar 2017 21:08:00 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: emacs-devel@gnu.org
> 
> > From: asjo@koldfront.dk (Adam Sjøgren)
> > Date: Sun, 26 Mar 2017 19:50:20 +0200
> > 
> > Applying this patch makes the problem go away for me (both in -Q and in
> > my regular setup).
> 
> Thanks.  Now I just have to make sure this still fixes the original
> bug...

Done, and the fix pushed.  Please test (the actual change is somewhat
different from the patch I asked you to try).

Thanks.

Re: Display updates strangely - extra text appears and then disappears

[Adam Sjøgren]

Eli writes:

> Done, and the fix pushed.  Please test (the actual change is somewhat
> different from the patch I asked you to try).

This works as well, both in -Q and normal setup.


  Cheers,

    Adam

-- 
 "So this is what being a morning person is like, I           Adam Sjøgren
  thought. It's like being 80 years old."                asjo@koldfront.dk

Re: Display updates strangely - extra text appears and then disappears

[Eli Zaretskii]

> From: asjo@koldfront.dk (Adam Sjøgren)
> Date: Sun, 26 Mar 2017 22:01:12 +0200
> 
> > Done, and the fix pushed.  Please test (the actual change is somewhat
> > different from the patch I asked you to try).
> 
> This works as well, both in -Q and normal setup.

Great, thanks.