GNU bug report logs - #61667
29.0.60; Failure to redisplay

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Message #461 received at 61667 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Po Lu <luangruo <at> yahoo.com>
Cc: 61667 <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>, gregory <at> heytings.org
Subject: Re: bug#61667: 29.0.60; Failure to redisplay
Date: Sat, 4 Mar 2023 14:45:00 +0200

On 04/03/2023 02:22, Dmitry Gutov wrote:
> On 04/03/2023 02:01, Po Lu wrote:
>>> But there is a persistent glitch: when the window configuration
>>> changes, 1 or 2 vertical bars often flash:
>>>
>>> https://a.uguu.se/iYTlOftH.mp4  (with emacs -Q)
>>>
>>> https://a.uguu.se/YdDWpMid.mp4  (with my config but with tool-bar and
>>> scroll-bar modes enabled)
>>>
>>> scroll-bar-mode on seems to be required to reproduce this.
>> This is expected: moving the scroll bar causes exposures, which can
>> cause flickering.  That's the problem double buffering is supposed to
>> fix.
> 
> Isn't it odd, though, that in both cases the glitch is positioned around 
> 1/2 of the scroll-bar's horizontal coordinate (relative to the left edge 
> of the frame)? When there is one scroll-bar, there is one glitch; when 
> there are two scroll-bars, there are two glitches.
> 
> My guess is that might be related to the display scale (2x).

And indeed: when I change the display scaling to 1x (no scaling), the 
"flashes" occur exactly above the scrollbars. Which looks significantly 
less jarring.

This seems like something we should be able to fix, if we're going to 
recommend disabling double-buffering as a fix for this and other problems.

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