Bug 431149

Summary:	https://invent.kde.org/plasma/plasma-workspace/-/commit/0d02ac8996db2d9fff8b3bf5e3e313a563a118af renders garbage on top of Plasma Dialogs (panels, tooltips, applets, notifications)
Product:	[Plasma] kwin	Reporter:	Nate Graham <nate>
Component:	compositing	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	kde, lbeltrame, plasma-bugs-null
Priority:	NOR	Keywords:	regression
Version First Reported In:	git master
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	Invisible panel and tooltip content Now there's weird stuff drawn on top

Description Nate Graham 2021-01-04 16:49:49 UTC

Created attachment 134545 [details]
Invisible panel and tooltip content

After https://invent.kde.org/plasma/plasma-workspace/-/commit/0d02ac8996db2d9fff8b3bf5e3e313a563a118af was committed, all of my Plasma surfaces implemented as a Plasma::Dialog are broken. They display no content, but all of it is actually there and interactive, just invisible.

Reverting that commit fixes the issue for me.

Reproduced on X11 both with and without Qt scaling enabled. Haven't tried Wayland yet; will shortly.

Comment 1 David Edmundson 2021-01-04 16:55:00 UTC

No-one else has reproduced. 

It also doesn't really make sense, it's only changing DesktopView. Plasma::dialog does not inherit from that

Comment 2 Nate Graham 2021-01-04 17:48:11 UTC

Reproduces with a clean build of everything.

Comment 3 Nate Graham 2021-01-04 18:02:39 UTC

(In reply to David Edmundson from comment #1)
> No-one else has reproduced. 
> 
> It also doesn't really make sense, it's only changing DesktopView.
> Plasma::dialog does not inherit from that
I agree, it makes no sense, and yet... it's happening. :(

Comment 4 Nate Graham 2021-01-04 18:54:06 UTC

A reboot fixed the issue. Restarting plasmashell and kwin and kdeinit and everything else did not fix it, but a reboot tit.

Comment 5 Nate Graham 2021-01-05 00:01:13 UTC

Nope, it started happening again. :( I noticed something interesting: killing kwin_x11 or disabling compositing fixes the problem immediately. It seems like KWin is compositing garbage on top of all plasma dialogs. Moving to KWin.

As before, reverting https://invent.kde.org/plasma/plasma-workspace/-/commit/0d02ac8996db2d9fff8b3bf5e3e313a563a118af still fixes the issue, for unknown reasons. Is is possible that setting the color to black for the desktop view affects how KWin does compositing for other Plasma surfaces?

Comment 6 Nate Graham 2021-01-05 00:03:33 UTC

Created attachment 134555 [details]
Now there's weird stuff drawn on top

Oh and the expression of the bug has changed slightly: now there are faint outlines of the correct content. See new attachment.

It looks like there's some kind of blending mode overlay on top of the panel.

Comment 7 Nate Graham 2021-01-05 02:00:47 UTC

This issue reproduces with git master KWin as well as the compositing re-work (https://invent.kde.org/plasma/kwin/-/merge_requests/507) so whatever's causing it, it seems fairly deep in KWin.

Comment 8 Vlad Zahorodnii 2021-01-05 07:27:09 UTC

I wouldn't jump to any conclusions yet, plasma renders panels and notifications differently depending on if compositing is active.

Can you check kwin support information when the panel is blank? Can you also take a screenshot of the panel when it's blank using Spectacle's "Window Under Cursor" mode? Just make sure that "Include window titlebar and borders" is unchecked, otherwise spectacle is going to use kwin's screenshot effect.

Comment 9 David Edmundson 2021-01-05 09:08:03 UTC

Reverted

Comment 10 David Edmundson 2021-01-05 10:32:13 UTC

For some context on the revert, it also affected bshah on mobile.

At some point I'll try and write a simple test without Qt with windows at different depths, so we can raise a driver bug.

Comment 11 Luca Beltrame 2021-01-06 13:28:18 UTC

I was affected the same way, and the reversion actually fixed the issue for me.