bug#13727: 24.3.50; terminal emacs flickers when redrawing frame

[Jose A. Ortega Ruiz]

On Sat, Feb 16 2013, Eli Zaretskii wrote:

>> From: "Jose A. Ortega Ruiz" <jao@gnu.org>
>> Date: Sat, 16 Feb 2013 02:38:51 +0100
>> 
>> Since a month ago, using emacs-snapshot (so pretty close to the Bzr
>> head), in terminal mode (both in xterm and urxvt), i'm experiencing
>> flickers and slow redraws in several modes.  Perhaps the easiest to
>> reproduce is using Gnus with a multiwindow layout (3 windows visible:
>> groups, message list and message body), where entering the next group
>> (which causes almost a complete redraw) produces a very noticeable
>> flicker, specially when the mode lines are redrawn.
>> 
>> For instance, right now, composing this bug report, the flicker is very
>> noticeable (perhaps due to the special self-deletable text in the
>> email?), although it comes and goes...
>> 
>> In vanilla emacs 24.2/3 the redraw is immediate and totally invisible.
>> 
>> I also sometimes see flickers when fontify region is doing its thing.
>
> Many changes went under the bridge during the last month.  Is it
> possible for you to bisect the last month worth of revisions to find
> the revisions that are to blame?

Not right now, but next weekend i should have time for it (i need to
learn how to do that with bzr first).

> If not, can you tell how to reproduce this with fontify region?  What
> exactly does the last sentence mean?

Sorry, i was guessing there.  When composing the bug message, and
sometimes in fontified buffers, i've got the impression of seeing the
window redisplaying itself, and it occurred to me that that redisplay
could be triggered by font-lock while fontifying: but it's just
guessing.

> I don't use Gnus; is there any other way to see the flickering?

I cannot reproduce the flickering with compose-message with -Q, and
sometimes not even with all my configuration loaded.  The "gnus effect"
is always there though... i'll keep trying reproducing it and report
back, and otherwise will eventually get to the bisecting.

Thanks for your patience!

Cheers,
jao