** Description changed:
+ [ Impact ]
+
Cursor sometimes stutters after heavy shell animations in 42.9 if there
is no GUI animation in response to its movement. And it doesn't stop
- stuttering until GUI redraws occur.
+ stuttering until GUI redraws occur (giving the frame clock an
+ opportunity to measure lower GPU usage).
This is different to the recent bug fix that probably caused it:
Bug 2023766:
* only occurs when moving over animated GUIs.
* never recovers or corrects itself.
* was spatial jittering at full frame rate.
* reduced the frame rate of the GUI below it.
This bug:
* only occurs when moving over non-animated GUIs.
* does recover and correct itself.
* is stuttering at seemingly half frame rate, but perfect spatially.
* does not reduce the frame rate of the the GUI below.
I think the reason we only see this in 42 (jammy) is because that
predates the change in the triple buffering algorithm to scale based on
"dynamic max render time" alone.
+
+ [ Test Plan ]
+
+ 1. Stress GNOME Shell maximally by repeatedly entering/leaving the
+ overview and/or scrolling the app grid.
+
+ 2. Stop suddenly and wiggle the mouse over some part of the desktop that
+ DOES NOT respond to mouse movement. Such as the wallpaper or some blank
+ grey space next to the app grid.
+
+ Expect: The mouse cursor does not get stuck in half frame rate.
+
+ [ Where problems could occur ]
+
+ In desktop frame timing since the clutter frame clock is being changed.
+ Although risk is minimal since we're just reverting to the pre-July
+ state of that code.
+
+ [ Other Info ]
+
+ The patch being dropped was found to not really be required in GNOME 42:
+ https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/2023766/comments/13
** Tags added: jammy
** Changed in: mutter (Ubuntu Jammy)
Status: New => In Progress
** Changed in: mutter (Ubuntu Jammy)
Importance: Undecided => Medium
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https://bugs.launchpad.net/bugs/2030959
Title:
Cursor sometimes stutters after heavy shell animations in 42.9
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