[Bug 2054510] Re: Incomplete screen redraws in virtual machines running Xorg

[Daniel van Vugt]

Here's the mantic debdiff for both bug 2054510 and bug 2051074.


** Changed in: mutter (Ubuntu Mantic)
       Status: Triaged => In Progress

** Patch added: "mutter_45.2-0ubuntu4.debdiff"
   https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/2054510/+attachment/5748404/+files/mutter_45.2-0ubuntu4.debdiff

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https://bugs.launchpad.net/bugs/2054510

Title:
  Incomplete screen redraws in virtual machines running Xorg

Status in Mutter:
  Fix Released
Status in mutter package in Ubuntu:
  Fix Committed
Status in mutter source package in Jammy:
  In Progress
Status in mutter source package in Mantic:
  In Progress
Status in mutter source package in Noble:
  Fix Committed

Bug description:
  [ Impact ]

  When using software rendering on Xorg (so usually just in VMs), some
  parts of app windows may fail to redraw.

  https://gitlab.gnome.org/GNOME/mutter/-/issues/2880

  [ Test Plan ]

  1. Set up a virtual machine without graphics acceleration.
  2. Log into 'Ubuntu on Xorg'.
  3. Open Settings > About and verify Graphics = llvmpipe and Windowing System = X11.
  4. sudo snap install chromium
  5. Open Chromium and find a web page with lots of text. Plain text without any links and staying at the top of the page will work best because you don't want to trigger any scrolling.
  6. Start selecting text with the mouse and while holding the button move the mouse up and down rapidly. Avoid triggering any page scrolling.
  7. Release the mouse button in roughly the middle of the area of text that was selected.
  8. Verify the remaining text selection is contiguous and not broken into multiple disconnected text selections (the bug).
  9. Repeat steps 7 and 8 several times to be sure.

  [ Where problems could occur ]

  The fix adds a new synchronization point between the compositor and X
  server. This should be inconsequential, although there is a "sync
  ring" in mutter used for this, and if a mistake occurs there then
  other parts of the desktop could appear to stop responding in Xorg
  sessions.

  [ Other Info ]

  This is a regression that started in 3.37.3 due to
  https://gitlab.gnome.org/GNOME/mutter/-/commit/551101c65cda.

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