https://bugs.kde.org/show_bug.cgi?id=512338
Bug ID: 512338
Summary: Does kde plan to support partial updates for QML
windows instead of full-surface repaint every frame?
Classification: Plasma
Product: kwin
Version First git master
Reported In:
Platform: Other
OS: Other
Status: REPORTED
Severity: normal
Priority: NOR
Component: compositing
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
When using QML in KWin/Plasma, every frame triggers a full-window repaint, even
when only a small region of the UI changes. This results in unnecessary GPU/CPU
workload.
I would like to ask whether KWin/Plasma has plans to support QML partial redraw
/ region-based damage tracking, similar to what Qt Quick can theoretically
provide.
STEPS TO REPRODUCE
Create a QML window with a small animated element (e.g. a blinking rectangle).
Run the QML scene under KWin/Plasma Wayland.
Observe with tools such as WAYLAND_DEBUG=1, KWin’s paint debug tools, or GPU
profiling.
OBSERVED RESULT
KWin repaints the entire surface every frame, even though only a very small
region changes in the QML scene.
This leads to increased GPU usage and unnecessary composition cost.
EXPECTED RESULT
Ideally, QML could provide partial-damage rectangles to the compositor, and
KWin would only repaint the regions that actually changed.
This behavior would greatly benefit performance on low-power devices and
animations that affect only small portions of the UI.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Any recent Plasma Wayland build
KDE Plasma Version: (your version)
KDE Frameworks Version: (your version)
Qt Version: (your Qt version)
ADDITIONAL INFORMATION
I am a developer working on QML scene optimization. I found that Qt Quick Scene
Graph is capable of tracking changed dirty regions internally, but currently
KWin treats QML surfaces as fully damaged for each frame.
I would like to ask:
Is there an existing plan or ongoing work for supporting partial damage for
QML-based windows?
If not, would such a feature be considered for future Plasma releases?
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