Bug 378144

Summary:	Hiding mouse cursor causes black flash
Product:	[Plasma] kwin	Reporter:	Roman Gilg <subdiff>
Component:	platform-drm	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	normal	CC:	brianaberts, carlosrfs99, notuxius, xaver.hugl
Priority:	NOR	Flags:	subdiff: Wayland+
Version First Reported In:	git master
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Roman Gilg 2017-03-27 08:38:40 UTC

Open Kate, move mouse cursor in text area. After short pause the cursor hides (as intended), i.e. DrmOutput::hideCursor() is called. Bug: A quick black flash appears from bottom till cursor position.

My guess is, that calling drmModeSetCursor(m_backend->fd(), m_crtc->id(), 0, 0, 0) in between presents is the cause.

We could:
* Try to synchronize it with present (difficult in legacy mode, possible in AMS after we introduced a cursor plane instead of using drmModeSetCursor).
* For hideCursor() instead of removing the cursor via drmModeSetCursor(..) show a transparent cursor image.

Comment 1 Martin Flöser 2017-04-02 09:03:50 UTC

rendering a transparent cursor instead seams fine to me as a workaround. Personally I have never seen this happening. Maybe driver bug?

Comment 2 Alexander Mentyu 2018-09-22 07:20:51 UTC

Cannot reproduce this bug both in Wayland and X11

Intel+NVIDIA video cards
Operating System: KDE neon Developer Edition
KDE Plasma Version: 5.14.80
Qt Version: 5.11.1
KDE Frameworks Version: 5.51.0
Kernel Version: 4.15.0-34-generic

Comment 3 Brian 2019-10-27 08:40:56 UTC

Can reproduce black flash in Wayland on 5.17.80

Operating System: Arch Linux 
KDE Plasma Version: 5.17.80
KDE Frameworks Version: 5.64.0
Qt Version: 5.13.1
Kernel Version: 5.3.6-arch1-1-fsync
OS Type: 64-bit
Processors: 12 × AMD Ryzen 5 2600 Six-Core Processor
Memory: 15.7 GiB of RAM
GPU: Sapphire RX 560 8GB
Mesa 19.3.0-devel (git-fe930ad92a) (Valve ACO)

Comment 4 Carlos Raimundo de Freitas Sotero 2020-02-29 22:50:15 UTC

i saw this bug on Fedora 33 Rawhide with Plasma 5.18.2 in wayland while was writing a script in kwrite. I tried to reproduce but i dont have any sucess.

Qt Version: 5.13.2
Kernel: 5.6 Release Candidate 3 (Fedora Rawhide default in 29/02/2020)
GPU: AMD Radeon Sapphire OC RX550 2GB Polaris12/Lexa Pro
Mesa: 20.0.0(Default too)

Comment 5 Zamundaaa 2023-09-21 12:11:23 UTC

5.18 is really old by now and I haven't seen this happen myself, so I assume this is no longer a problem. If it is still reproducible in 5.27, just reopen the bug report