https://bugs.kde.org/show_bug.cgi?id=505558
Bug ID: 505558
Summary: Brightness OSD - No feedback at 100% and inconsistent
behavior leading to inability to increase brightness
Classification: Plasma
Product: plasmashell
Version First 6.3.5
Reported In:
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Power management & brightness
Assignee: plasma-b...@kde.org
Reporter: hsanta...@gmail.com
Target Milestone: 1.0
I. Summary
This report details two related issues concerning screen brightness control in
the KDE Plasma environment:
When the screen brightness is already at its maximum level (100%), pressing
the designated shortcut key to increase brightness (e.g., Fn+F6) elicits no
visual feedback via the On-Screen Display (OSD). This behavior is inconsistent
with the volume control OSD, which does provide feedback even when the volume
is at 100%.
A more critical issue arises when the Plasma shell incorrectly assumes the
brightness is at 100% (even when it is not). In this state, attempts to
increase brightness using the shortcut key fail to produce any change in
brightness or any OSD feedback. To increase brightness, the user must first
decrease it, after which the increase function becomes responsive again, and
the OSD appears as expected.
This behavior, particularly the lack of OSD feedback at maximum brightness,
appears to be a regression of a previously fixed issue (Bug #387284).
II. Environment
Operating System: Arch Linux
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.1
Kernel Version: 6.12.33-1-lts (64-bit)
Graphics Platform: Wayland
Processors: 12 × Intel® Core™ i7-10750H CPU @ 2.60GHz
Memory: 15.4 GiB of RAM
Graphics Processor 1: NVIDIA GeForce GTX 1650
Graphics Processor 2: Intel® UHD Graphics
Manufacturer: LENOVO
Product Name: 82CG
System Version: IdeaPad Gaming 3 15IMH05
III. Steps to Reproduce
Scenario 1: No OSD feedback when brightness is at 100%
Manually increase the screen brightness to its maximum level (100%) using
the brightness control shortcut keys (e.g., Fn+F6).
Observe that the brightness OSD appears during the increase.
Once at 100% brightness, press the "increase brightness" shortcut key
again.
Scenario 2: Inability to increase brightness when Plasma incorrectly assumes
100%
This state may occur under conditions not yet fully identified, but it
manifests as the system believing brightness is at 100% when it is observably
lower.
Attempt to increase screen brightness using the "increase brightness"
shortcut key (e.g., Fn+F6).
Observe the brightness level and whether an OSD appears.
If no change occurs, press the "decrease brightness" shortcut key (e.g.,
Fn+F5) once or multiple times.
Observe that the brightness decreases and the OSD appears.
Now, press the "increase brightness" shortcut key again.
IV. Actual Results
Scenario 1:
When the "increase brightness" shortcut key is pressed while brightness is
already at 100%, there is no OSD pop-up to indicate the current brightness
level or that it is at its maximum. The system provides no visual feedback that
the command was received or processed.
Scenario 2:
When attempting to increase brightness (step III.2.2), the screen
brightness does not change, and no OSD appears. It gives the impression that
the key press was not registered or that the brightness control is
unresponsive.
After decreasing the brightness (step III.2.4), attempting to increase
brightness again (step III.2.6) now successfully increases the brightness, and
the OSD appears as expected, showing the current brightness level.
V. Expected Results
Scenario 1:
When the "increase brightness" shortcut key is pressed and the brightness
is already at 100%, the OSD should appear, displaying the current brightness
level (100%) and indicating that it is at the maximum. This behavior would be
consistent with the volume OSD, which appears and shows "100%" when attempting
to increase volume beyond its maximum. This consistency is important for user
experience and feedback.
Scenario 2:
The Plasma shell should accurately reflect the actual screen brightness.
If the brightness is not at 100%, pressing the "increase brightness"
shortcut key should always increase the brightness and display the OSD with the
updated level.
It should not be necessary to first decrease brightness to enable the
increase brightness functionality when the actual brightness is below maximum.
VI. Additional Information and Analysis
The observed lack of OSD feedback when attempting to increase brightness at
100% is inconsistent with other system feedback mechanisms, such as the volume
control. The volume OSD correctly provides feedback even when the volume is at
its maximum or minimum. This inconsistency can lead to user confusion, as it
may seem like the brightness shortcut key is not functioning.
More significantly, this specific issue (lack of OSD at 100%) appears to be a
regression. Bug #387284 ("Brighness Key Show When Brightness is 100%")
addressed this exact problem, stating, "When the brightness is already at the
maximum (or minimum) value, hitting the keyboard shortcut to increase (resp.
decrease) it does not bring up the OSD, there is no visual feedback. This is
not consistent either with the volume which handles this correctly." This bug
was marked as RESOLVED FIXED in Powerdevil 5.14.0, with the associated commit
4b8ae4d708a6f4cc854ea82ca96987f0b47ea722. The re-emergence of this behavior
suggests that the previous fix may have been inadvertently reverted or is no
longer effective in current versions.
The second scenario, where Plasma incorrectly believes brightness is at 100%
and prevents increases until a decrease is performed, is a more severe
usability impediment. It directly hinders the user's ability to control a
fundamental aspect of their display. This "false 100%" state could potentially
be related to how KWin and PowerDevil interact regarding brightness settings.
For instance, there are observations in other contexts (Bug #494408, Comment 4)
where "KWin defaults the brightness of every monitor to 100%... KWin will ask
PowerDevil to max out the brightness for any display without this entry, even
if hardware brightness is currently lower than max". While that bug discusses a
different specific scenario (brightness resetting on session startup/monitor
wake-up), the described mechanism of KWin instructing PowerDevil to set maximum
brightness could be a factor in the system erroneously concluding that
brightness is at 100%, thus ignoring further increase commands until the state
is reset by a decrease action. This suggests a potential area for investigation
into the state management of brightness levels within Plasma.
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