Random window repaints missing if happen together with title change

Bug #2002456 reported by Fenix Elfmz
8
This bug affects 1 person
Affects Status Importance Assigned to Milestone
xwayland (Ubuntu)
New
Undecided
Unassigned

Bug Description

System: Ubuntu 22.04.1 LTS
Hardware: VmWare on i7 3770 configured with 4 CPUs, but wild users from field reported same issue on different hardware.
Option 1: User logged in locally through Ubuntu on XOrg option in login screen.
Option 2: User logged in remotely via xrdp protocol that uses XOrg.

Problem manifested as sporadic missing repaints of application. Debugging shows that missing repaints happen in case window title text changed just before window image repainting.
Was able to create minimalistic X11 test application that on each keypress: changes titlebar to random string and (immediately) paints some string inside. From time to time titlebar changed but content inside is not painted, although according to debug prints expose events arrived correctly all the time. However if in such situation try to move window by grabbing its titlebar using mouse (sometimes its enough just to move mouse over) - then content gets updated to correct one and (according to debug printouts) this happens without getting expose events by application.

Attached: source code of demo application and will try to attach also video recording of demonstration.
Note that bug highly depends on timings (likely its a race condition somewhere in XWayland or Window Manager and there is loop in code attenuated for highest reproduction rate on my system. On other systems it may need adjustements.

Revision history for this message
Fenix Elfmz (elfmz) wrote :
Revision history for this message
Fenix Elfmz (elfmz) wrote :

Here is video record of reproduction... Hope it will upload//

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