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

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Daniel van Vugt (vanvugt):

[ 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.

** Affects: mutter
     Importance: Unknown
         Status: Fix Released

** Affects: mutter (Ubuntu)
     Importance: Medium
     Assignee: Daniel van Vugt (vanvugt)
         Status: Fix Committed

** Affects: mutter (Ubuntu Jammy)
     Importance: Medium
     Assignee: Daniel van Vugt (vanvugt)
         Status: In Progress

** Affects: mutter (Ubuntu Mantic)
     Importance: Medium
     Assignee: Daniel van Vugt (vanvugt)
         Status: Triaged

** Affects: mutter (Ubuntu Noble)
     Importance: Medium
     Assignee: Daniel van Vugt (vanvugt)
         Status: Fix Committed


** Tags: fixed-in-mutter-46.0 fixed-upstream jammy mantic noble regression-release udeng-1928
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Incomplete screen redraws in virtual machines running Xorg
https://bugs.launchpad.net/bugs/2054510
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