[Bug 2023209] [NEW] Windows get wrong z-index and flickering decoration halo

[Launchpad Bug Tracker]

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Frequently, windows such as the new text editor, or the nautilus file
browser, or modal dialogs seem to have an in valid z-index, i.e. I
cannot click the title bar, and the window is virtually behind
everything.  The window also has a flickering halo full of garbage from
other screen areas which looks like missallocated texture memory?  It is
possible to bring the window into the foreground, bu e.g. TABing through
the applications but it cannot be used because other windows that are
'behind' it capture the mouse events through this window.  This can
happen with many Windows at the same time, typically after sleep-wake.
The Windows can be rescued into normal state by using keyboard shortcuts
to maximize-minimize, after which everything is fine.  The z-index is
correct, mouse events are captured and the decorations look perfect.

This started happening with Ubuntu 22.10 and is still present in 23.04,
so I assume that it is a bug in Gnome 43?  This happens regularly after
sleep wake which, in my case, often comes with a zoom switch between
100% (external monitor on dock) and 200% (internal HiDPI laptop screen).
I am running Ubuntu on xorg, not Wayland, because screen-sharing
individual windows with Zoom does not work on Wayland.  I am observing
this most frequently with Snap apps such as Nautilus and the new text
editor, but also Evolution dialogs have come up with this.  May be a
timing issue that manifests more frequently with the slower snap apps?

I understand that this bug-report is unsatisfying in how to reproduce
this, and what exactly the outcome is, but it is pretty random in nature
and I can only report the visual/ GUI outcome.  I am happy to provide
additional input as requested.

** Affects: ubuntu-meta (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: bot-comment
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Windows get wrong z-index and flickering decoration halo
https://bugs.launchpad.net/bugs/2023209
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