[Bug 2064716] Re: gnome-terminal darkened by visual bell during screensaver

[Nick Rosbrook]

I don't see anything actionable for ubuntu-sponsors, so unsubscribing.

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https://bugs.launchpad.net/bugs/2064716

Title:
  gnome-terminal darkened by visual bell during screensaver

Status in GNOME Terminal:
  Fix Released
Status in mutter package in Ubuntu:
  Fix Released
Status in mutter source package in Noble:
  Fix Committed
Status in mutter source package in Plucky:
  Fix Released
Status in mutter source package in Questing:
  Fix Released

Bug description:
  [ Impact ]

   * Compositor based visual effects while screensaver is running can render
     some windows unusable. One such instance is visual bells in gnome-terminal
     will leave the window darkened if they occur during that time. This is due
     to the compositor skipping but not reverting the transition.

   * The backported change restores the initial state when effects transitions
     are skipped (e.g. while screen is locked).

   * Although the bug has been reported against gnome-terminal, it could
     affect other applications or extensions making use of opacity transitions.

  [ Test Plan ]

   * launch a fresh instance:
     lxc launch images:ubuntu/24.04/desktop testvm --vm
     lxc console d --type vga

   * gsettings set org.gnome.desktop.wm.preferences visual-bell-type frame-flash;
     gsettings set org.gnome.desktop.wm.preferences visual-bell true;
     xdg-screensaver activate; sleep 2; echo -e \\a;

   * The terminal window should not remain opaque when exiting the
  screen saver.

  
  [ Where problems could occur ]

   * The opacity transition functionality is used in a handful of applications,
     by the gnome desktop and by extensions.

   * This change is very small in scope, but could affect the window-flashing
     functionality on gnome mutter. It possibly could interfere with
     window opacity as it is one of the affected attributes of the flash
     transition.

   * The patch has already been included with mutter 47+ and newer Ubuntu
     releases for more than a year without issue.

  [ Original Descriptiption ]

  Problem: visual bell during screensaver turns terminal very dark with
  no remedy.

  Reproducing:

  - Settings -> Accessibility -> Hearing -> Visual Alerts -> On
    (Flash the entire Window)

  - Open a gnome-terminal

  - Ensure volume is not muted

  - type: xdg-screensaver activate; printf '\a'

  - Wake up the screensaver, and notice that the window in which there
  was a bell, is darker.

  Tested and reproduced on:

  - Jammy (2024-06-15)
  - Noble (2024-07-04)

  ---------------------
  Original ticket below
  vvvvvvvvvvvvvvvvvvvvv

  ========
  Symptoms
  ========

  Sometimes, when coming back to my laptop, and unlocking an existing
  GNOME session, I find that my gnome-terminal has turned very dark. I
  have found no triggers (other than session unlock) and no fixes to
  undo the darkness.

  It looks like this:

  https://junk.devs.nu/2024/lp2064716-gnome-terminal-turned-dark/gnome-terminal-very-dark-on-the-right.png
  ( https://bugs.launchpad.net/ubuntu/+source/gnome-terminal/+bug/2064716/+attachment/5774287/+files/gnome-terminal-very-dark-on-the-right.png )

  The window on the right is the one I found after unlocking my GNOME
  session. The window on the left was a second terminal I started, which
  has the normal brightness.

  Using some color picking, I can say that the brightness has been
  reduced by 70%-85%.

  Here's an animation of the window:

  https://junk.devs.nu/2024/lp2064716-gnome-terminal-turned-dark/gnome-terminal-turned-very-dark.webm
  ( https://bugs.launchpad.net/ubuntu/+source/gnome-terminal/+bug/2064716/+attachment/5774288/+files/gnome-terminal-turned-very-dark.webm )

  The video shows:
  - The dark window in a smaller state;
  - settings are opened, and switched to bright colors;
  - both the good and the bad terminals get lighter, but the bad terminal is still way too dark;
  - moving the window to the right shows a glitch in the glitch where the bottom-most row has normal colors.

  ========
  Versions
  ========

  - Ubuntu Jammy 22.04 (many versions)
  - gnome-terminal 3.44.0-1ubuntu1
  - libmutter 42.9-0ubuntu7

  I thought it might be a Wayland thing, but I switched back to Xorg
  recently and the problem wasn't gone. I've not seen this bug with
  Focal. And my colleagues haven't seen the bug either.

  ========
  Followup
  ========

  I have no idea where to look further. I did some probing with xprop on
  the window, that gave me no useful info, and may likely not be
  relevant as Wayland is also affected.

  Any suggestions to get to the bottom of this is appreciated.

  Unfortunately, I don't know how to trigger the bug. I always have
  terminals open, and only 1% of the time (ball park) when unlocking
  does this occur.

  Let me know. Cheers!
  Walter Doekes

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