https://bugs.kde.org/show_bug.cgi?id=520878
Bug ID: 520878
Summary: Color Picker samples the magnified cursor instead of
the pixel beneath it when the Zoom effect is active
Classification: Plasma
Product: kwin
Version First 6.6.5
Reported In:
Platform: Fedora RPMs
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: effects-various
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
When the KWin Zoom accessibility effect is active (e.g. zoomed in to pixel
level via the 3-finger Accessibility gesture), invoking the Plasma Color Picker
returns the color of the mouse cursor itself rather than the pixel behind it.
At high zoom the magnified cursor covers the target pixel, so the picker reads
the cursor's own pixels instead of the underlying screen pixel.
STEPS TO REPRODUCE
1. Plasma Wayland session. Add the Color Picker widget to a panel.
2. Enable the Zoom effect (System Settings → Accessibility → Zoom) and zoom in
to near pixel level.
3. Hover the cursor over a known-colored pixel and trigger Color Picker → Pick.
OBSERVED RESULT
The picker returns the cursor's color (e.g. the center of the crosshair
cursor), not the underlying pixel.
EXPECTED RESULT
The picker returns the color of the pixel under the cursor hotspot, regardless
of the Zoom effect.
LIKELY CAUSE
The ColorPicker effect samples the final rendered scene at the cursor position.
The Zoom effect (MousePointer=Scale, the default) composites a magnified cursor
into that scene, so the picker reads the cursor's pixels.
CORROBORATION / WORKAROUND
Setting [Effect-zoom] MousePointer=Hide in kwinrc (hide the cursor while
zoomed) makes the picker grab the correct pixel — which supports the cause
above.
SOFTWARE/OS VERSIONS
KWin 6.6.5, Plasma 6.6.5, Frameworks/Qt 6.11.1, Fedora Linux 44, Wayland
session.
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