https://bugs.kde.org/show_bug.cgi?id=496721
Bug ID: 496721
Summary: No error message when selecting invalid generated
modes
Classification: Plasma
Product: KScreen
Version: 6.2.3
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: common
Assignee: kscreen-bugs-n...@kde.org
Reporter: timo.vel...@hotmail.de
Target Milestone: ---
Created attachment 176150
--> https://bugs.kde.org/attachment.cgi?id=176150&action=edit
dmesg output after enabling verbose DRM logging
SUMMARY
Some of the modes the kscreen kcm displays are generated modes (see
https://invent.kde.org/plasma/kwin/-/commit/9ed87a4e23dea212dadd86d4463e7fdfe6aafc84).
As a particular display is not guaranteed to support these, applying them might
fail. However, there does not seem to be an error message in this case.
Instead, the mode is just silently not applied.
What makes this even worse, is that the UI is not updated. That is, the "Apply"
button is grayed out, and the resolution selection also displays the wrong
resolution (the one that just failed to apply properly).
STEPS TO REPRODUCE
1. Select any of the generated resolutions, in my case e.g. 1920x1200 (16:10)
at the only available refresh rate 60 hertz.
2. Click apply.
Note that I have a somewhat peculiar laptop display; according to its EDID it
only supports a single mode, namely 2880x1800 @ 89.999860 Hz.
OBSERVED RESULT
The screen resolution does not change, however, the "Apply" button is now
grayed out (as if the operation was successful).
Unfortunately, on default logging settings, there is also no mention of this
when checking journalctl. So there really is no indication at all to the user
that something just went wrong.
EXPECTED RESULT
The screen resolution changes, or an error message is shown.
SOFTWARE/OS VERSIONS
KDE Plasma 6.2.3 on Fedora 41
Intel integrated GPU (i915)
ADDITIONAL INFORMATION
In my particular case, I traced the resolution setting to fail at
https://invent.kde.org/plasma/kwin/-/blob/0e9f1e721c7b45b6b7d31a44df925483c1ec1155/src/backends/drm/drm_pipeline.cpp#L115.
I also collected some more logging information using the procedure outlined
here (https://github.com/swaywm/wlroots/wiki/DRM-Debugging) and have attached
the full log of doing the steps I outlined above. I think the interesting line
is
[CONNECTOR:241:eDP-1] Requested mode vrefresh (60 Hz) does not match fixed mode
vrefresh (90 Hz)
Which I interpret to mean that my display just flat out rejects modes that do
not use 90 Hz.
On a related note, I think KWin should generate more display modes by default.
GNOME does this.
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