Bug 455124

Summary:	[VLC] Playback panel is not aligned to the bottom in full screen mode
Product:	[Plasma] plasmashell	Reporter:	popov895 <popov895>
Component:	general	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED DOWNSTREAM
Severity:	normal	CC:	kde, nate, popov895
Priority:	NOR
Version First Reported In:	5.24.5
Target Milestone:	1.0
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	Playback panel in full screen mode

Description popov895 2022-06-10 13:08:03 UTC

Created attachment 149597 [details]
Playback panel in full screen mode

SUMMARY

It may seem to you that this is clearly a VLC bug, but same bug has already been reported on VLC bug tracker and closed because "we do nothing special when it comes to KDE" (https://code.videolan.org/videolan/vlc/-/issues/22563). And actually, the playback panel is aligned to the bottom in full screen mode everywhere, except for KDE (both X11 and Wayland). What's interesting is if you move the taskbar up (or to the side), then the playback panel becomes aligned to the bottom. Is it KDE or Qt bug?

STEPS TO REPRODUCE

1. Open any video
2. Switch to full screen mode

OBSERVED RESULT

Playback panel is not aligned to the bottom.

EXPECTED RESULT

Playback panel is aligned to the bottom.

SOFTWARE/OS VERSIONS

Operating System: openSUSE Tumbleweed 20220606
KDE Plasma Version: 5.24.5
KDE Frameworks Version: 5.94.0
Qt Version: 5.15.2

Comment 1 Nate Graham 2022-06-10 15:35:25 UTC

They may do nothing special for KDE, but they're clearly using a positioning API that takes into account the Plasma Panel position when determining placement. I am not aware of anything in Qt that would do this, since Plasma Panels are added in our code, not Qt. However it's possible I'm wrong and something in Qt does respect that due to the window flags we set on Plasma Panels. If so, they should use a different API for positioning the playback overlay that doesn't care about it.

This needs investigation by VLC's developers. It's an app bug or a Qt bug, but it can't possibly be a KDE bug.

Comment 2 popov895 2022-06-10 23:30:43 UTC

The reason for this behavior is that the X11 doesn't allow to move a window outside the available screen geometry. Any idea how to get around this?

Comment 3 Nate Graham 2022-06-10 23:54:53 UTC

The Plasma Panel isn't beyond the screen geometry, though. Qt won't see it that way at least.

Comment 4 popov895 2022-06-11 09:43:26 UTC

The Plasma Panel in NormalPanel mode sets the "strut" of itself (https://invent.kde.org/plasma/plasma-workspace/-/blob/master/shell/panelview.cpp#L1314), causing the VLC's playback panel can no longer be placed over the Plasma Panel. This is not a KDE bug, but an X11 (or KWin?) feature. But I have not yet found a solution how to get around this feature.

Comment 5 Nate Graham 2022-06-11 13:58:36 UTC

Yes, the panel sets struts, but those are only take into account when KWin positions a window. If this is affecting VLC, is means the overlay is internally drawn as a separate window, which is probably not an ideal implementation. It should simply be drawn and positioned internally, by VLC itself.