GNU bug report logs - #16621
24.3.50; Periodic timer + overlays = flickering near point

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Dmitry Gutov <dgutov <at> yandex.ru>
Subject: bug#16621: closed (Re: [Emacs-diffs] master c290715: Add
 double-buffering support to reduce flicker)
Date: Wed, 25 Jan 2017 02:22:03 +0000

[Message part 1 (text/plain, inline)]

Your bug report

#16621: 24.3.50; Periodic timer + overlays = flickering near point

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 16621 <at> debbugs.gnu.org.

-- 
16621: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=16621
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Dmitry Gutov <dgutov <at> yandex.ru>
To: emacs-devel <at> gnu.org, Daniel Colascione <dancol <at> dancol.org>
Cc: 12363-done <at> debbugs.gnu.org, 16621-done <at> debbugs.gnu.org
Subject: Re: [Emacs-diffs] master c290715: Add double-buffering support to
 reduce flicker
Date: Wed, 25 Jan 2017 05:21:03 +0300

Version: 26.1

On 29.10.2016 05:30, Daniel Colascione wrote:
> branch: master
> commit c29071587c64efb30792bd72248d3c791abd9337
> Author: Daniel Colascione <dancol <at> dancol.org>
> Commit: Daniel Colascione <dancol <at> dancol.org>
>
>     Add double-buffering support to reduce flicker

I'd like to add my belated gratitude. This is the kind of change that 
makes me happier to use Emacs and to continue contributing.

Thanks, Daniel!

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From: Dmitry Gutov <dgutov <at> yandex.ru>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3.50; Periodic timer + overlays = flickering near point
Date: Sun, 02 Feb 2014 03:01:26 +0200

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It happens with different overlays, and with the default monospaced font
of my system (Ubuntu GNU/Linux), but it's easiest to reproduce doing
isearch, and using Fira Mono (TrueType version, available from
https://www.mozilla.org/en-US/styleguide/products/firefox-os/typeface/,
see the bottom of the page). Steps from emacs -Q:

1. Evaluate (run-at-time nil 0.01 'ignore)

2. Evaluate (set-face-attribute 'default nil :height 105 :family "Fira Mono")

This is optional, but with the default font the flickering is harder to
reproduce.

3. Open a text file press C-s (or C-r), enter some letters, preferably
common to that file, press C-s or C-r again. Repeat multiple times.
Maybe do that for a couple of minutes, even.

4. Observe flickering letters, usually one to the left, or one to the
right of the cursor.

Most of the time the flickering happens 2 or 3 times and stops, but I've
managed to record a couple of semi-stable loops of this on video, see
the attachment. It demonstrates a somewhat extreme situation, usually I
only see flickering once every handful searches or so.

This is in no way limited to isearch. For example, I can also see it
when typing, when using the fancy highlight-tail-mode
(http://www.emacswiki.org/emacs-en/highlight-tail.el), at least with
settings highlight-tail-steps 14, highlight-tail-timer 0.02.

Let me know if the video format (h264) is not acceptable.

In GNU Emacs 24.3.50.5 (x86_64-unknown-linux-gnu, GTK+ Version 3.8.6)
 of 2014-02-01 on axl
Repository revision: 116234 dgutov <at> yandex.ru-20140201170608-2rn2phrkukqt84gm
Windowing system distributor `The X.Org Foundation', version 11.0.11405000
System Description:	Ubuntu 13.10

[Screencast 2014-02-02 02:32:44.mp4 (video/mp4, attachment)]

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