bug#28652: 26.0.60; Display often "flashes" due to double buffering when switching to Emacs frames

bug#28652: 26.0.60; Display often "flashes" due to double buffering when switching to Emacs frames

[N. Jackson]

When switching between windows in Gnome using Alt-Tab there is
often a bright flash just after switching to an Emacs frame.

It seems as if the Emacs frame is displayed and then a window of
some other application appears for a fraction of a second before
the display settles down to the showing the Emacs frame.

Because the flash is so quick, I Initially thought the Emacs frame
was being displayed in white before being painted to it's correct
display, but this is not the case. By choosing distinctive colours
or distinctive images in my other applications, I can tell that it
is the window of another application that is flashing up.

[This flashing might be particularly noticeable on this system as
I use a dark theme in Emacs (Wheatgrass) and most other
application windows are predominantly white. Also I keep all my
Emacs frames and all my other application windows maximised or
full screen (because I have a small display).]

This flashing does not happen in Emacs 24 or 25. It happens in
Emacs 26 and I think I also saw it when I built master back in
March [1].

However, it does not happen in Emacs 26 if I put

  (add-to-list 'default-frame-alist '(inhibit-double-buffering . t))

in my init file and restart Emacs.

[1] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25851#170
    

In GNU Emacs 26.0.60 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.17)
 of 2017-09-24 built on moondust.localdomain
Repository revision: d93301242f38d3d9aaa55899c07496f0bdecf391
Windowing system distributor 'Fedora Project', version 11.0.11903000
System Description:	Fedora release 25 (Twenty Five)

Configured using:
 'configure --without-pop 'CFLAGS=-O2 -g3 -gdwarf-4''

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GSETTINGS NOTIFY ACL
LIBSELINUX GNUTLS LIBXML2 FREETYPE LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS
GTK3 X11 LCMS2

Important settings:
  value of $LANG: en_CA.UTF-8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix

Major mode: Text

Minor modes in effect:
  diff-auto-refine-mode: t
  flyspell-mode: t
  pdf-occur-global-minor-mode: t
  shell-dirtrack-mode: t
  recentf-mode: t
  display-battery-mode: t
  display-time-mode: t
  show-paren-mode: t
  savehist-mode: t
  save-place-mode: t
  electric-pair-mode: t
  desktop-save-mode: t
  delete-selection-mode: t
  cua-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  temp-buffer-resize-mode: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  global-visual-line-mode: t
  visual-line-mode: t
  transient-mark-mode: t

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Features:
(shadow emacsbug misearch multi-isearch mm-archive mailalias smtpmail
gnus-html url-queue help-fns radix-tree browse-url xml url-cache mm-url
url url-proxy url-privacy url-expand url-methods url-history url-cookie
url-domsuf url-util bbdb-message sendmail sort smiley gnus-cite
gnus-async gnus-bcklg nnir qp mail-extr gnus-ml disp-table hl-line
nndraft nnmh utf-7 server pinentry epa-file network-stream nsm starttls
nnfolder bbdb-gnus bbdb-mua nnnil gnus-agent gnus-srvr gnus-score
score-mode nnvirtual gnus-msg nntp gnus-cache cl-extra help-mode vc-git
diff-mode map flyspell ispell pdf-occur ibuf-ext ibuffer
ibuffer-loaddefs tablist tablist-filter semantic/wisent/comp
semantic/wisent semantic/wisent/wisent semantic/util-modes semantic/util
semantic semantic/tag semantic/lex semantic/fw mode-local cedet
pdf-isearch let-alist pdf-misc imenu pdf-tools compile cus-edit pdf-view
bookmark pp pdf-cache pdf-info tq pdf-util org-contacts org-capture
gnus-art mm-uu mml2015 mm-view mml-smime smime dig mailcap gnus-sum
gnus-group gnus-undo gnus-start gnus-cloud nnimap nnmail mail-source tls
gnutls utf7 netrc nnoo parse-time gnus-spec gnus-int gnus-range message
subr-x puny rfc822 mml mml-sec epa derived epg mm-decode mm-bodies
mm-encode mail-parse rfc2231 gmm-utils mailheader gnus-win gnus nnheader
org-duration org-eldoc org-w3m org-rmail org-mhe org-irc org-info
org-habit org-gnus gnus-util rmail rmail-loaddefs rfc2047 rfc2045
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bug#28652: 26.0.60; Display often "flashes" due to double buffering when switching to Emacs frames

[martin rudalics]

 > In GNU Emacs 26.0.60 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.17)
 >   of 2017-09-24 built on moondust.localdomain

If this happened for a build of master in between commits

c0af83b6ccf2dab9a515dd7f52eb9d4500275ae3

and

2fa19cc5510cdbf00c54991a9959be984dd99fbe

it would imply that inhibiting double buffering is also needed even if
it did not cause problems like those from bug#28589.  But apparently you
built from the release branch.  So I'm slightly confused.

martin

bug#28652: 26.0.60; Display often "flashes" due to double buffering when switching to Emacs frames

[N. Jackson]

At 10:32 +0200 on Saturday 2017-09-30, martin rudalics wrote:
>
>> In GNU Emacs 26.0.60 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.17)
>>   of 2017-09-24 built on moondust.localdomain
>
> If this happened for a build of master in between commits
>
> c0af83b6ccf2dab9a515dd7f52eb9d4500275ae3
>
> and
>
> 2fa19cc5510cdbf00c54991a9959be984dd99fbe
>
> it would imply that inhibiting double buffering is also needed
> even if it did not cause problems like those from bug#28589. But
> apparently you built from the release branch. So I'm slightly
> confused.
>
> martin

Hi Martin,

Sorry, I don't know if I can help with your confusion.

Yes, I built from the release branch (emacs-26) on 2017-09-24 at
commit d93301242f38d3d9aaa55899c07496f0bdecf391.

The commits you mention were made 2017-08-27 and 2017-09-26
respectively, but neither of them seem to be in the emacs-26
branch.

I am not familiar with bug#28589.

N.

bug#28652: 26.0.60; Display often "flashes" due to double buffering when switching to Emacs frames

[martin rudalics]

 > Yes, I built from the release branch (emacs-26) on 2017-09-24 at
 > commit d93301242f38d3d9aaa55899c07496f0bdecf391.
 >
 > The commits you mention were made 2017-08-27 and 2017-09-26
 > respectively, but neither of them seem to be in the emacs-26
 > branch.

Then this was pure coincidence and you're facing a more general issue
with double buffering.

martin

bug#28652: 26.0.60; Display often "flashes" due to double buffering when switching to Emacs frames

[Lars Ingebrigtsen]

nljlistbox2@gmail.com (N. Jackson) writes:

> When switching between windows in Gnome using Alt-Tab there is
> often a bright flash just after switching to an Emacs frame.
>
> It seems as if the Emacs frame is displayed and then a window of
> some other application appears for a fraction of a second before
> the display settles down to the showing the Emacs frame.
>
> Because the flash is so quick, I Initially thought the Emacs frame
> was being displayed in white before being painted to it's correct
> display, but this is not the case. By choosing distinctive colours
> or distinctive images in my other applications, I can tell that it
> is the window of another application that is flashing up.
>
> [This flashing might be particularly noticeable on this system as
> I use a dark theme in Emacs (Wheatgrass) and most other
> application windows are predominantly white. Also I keep all my
> Emacs frames and all my other application windows maximised or
> full screen (because I have a small display).]

(I'm going through old bug reports that unfortunately weren't resolved
at the time.)

I'm also using Gnome (I'm on Debian bullseye), but I can't see these
flashes (I've tried in Emacs 26.1 and Emacs 28) when Alt-Tab-ing between
something that has a bright background and Emacs (which has a black
background).

Are you still seeing this in recent Emacs/Gnome versions?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#28652: 26.0.60; Display often "flashes" due to double buffering when switching to Emacs frames

[N. Jackson]

Hello Lars,

At 09:57 +0200 on Friday 2021-09-03, Lars Ingebrigtsen wrote:
>
> nljlistbox2@gmail.com (N. Jackson) writes:
>
>> When switching between windows in Gnome using Alt-Tab there is
>> often a bright flash just after switching to an Emacs frame.
>>
>> It seems as if the Emacs frame is displayed and then a window of
>> some other application appears for a fraction of a second before
>> the display settles down to the showing the Emacs frame.
>>
>> Because the flash is so quick, I Initially thought the Emacs frame
>> was being displayed in white before being painted to it's correct
>> display, but this is not the case. By choosing distinctive colours
>> or distinctive images in my other applications, I can tell that it
>> is the window of another application that is flashing up.
>>
>> [This flashing might be particularly noticeable on this system as
>> I use a dark theme in Emacs (Wheatgrass) and most other
>> application windows are predominantly white. Also I keep all my
>> Emacs frames and all my other application windows maximised or
>> full screen (because I have a small display).]
>
> (I'm going through old bug reports that unfortunately weren't resolved
> at the time.)
>
> I'm also using Gnome (I'm on Debian bullseye), but I can't see these
> flashes (I've tried in Emacs 26.1 and Emacs 28) when Alt-Tab-ing between
> something that has a bright background and Emacs (which has a black
> background).
>
> Are you still seeing this in recent Emacs/Gnome versions?

No, I haven't seen this problem -- at all -- in quite a few Emacs
versions.

(Sorry I didn't update the bug report with that information -- I had
completely forgotten about the bug.)

[The only time I see any "flashing" of any sort in Emacs now is
while it starts up and restores my desktop frames and windows. My
understanding is that this is expected. (It is also much less
frenetic that it was in the past.)]

Thank you and best regards,
Neil.

bug#28652: 26.0.60; Display often "flashes" due to double buffering when switching to Emacs frames

[Lars Ingebrigtsen]

"N. Jackson" <nljlistbox2@gmail.com> writes:

> No, I haven't seen this problem -- at all -- in quite a few Emacs
> versions.
>
> (Sorry I didn't update the bug report with that information -- I had
> completely forgotten about the bug.)

No problem.  :-)  I'm closing this bug report, then.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no