https://bugs.kde.org/show_bug.cgi?id=495884

Olivia Laari <[email protected]> changed:

           What    |Removed                     |Added
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                 CC|                            |[email protected]

--- Comment #4 from Olivia Laari <[email protected]> ---
This issue is still very much making any resize/scale op effectively unusable
on Wayland. I added a short screen recording as an attachment to actually show
how awful the performance is.

I also attached output of gdb (with symbols), which i took while kolourpaint
was blocking during the resize. Also during the resize top -H shows only
kolourpaints main thread doing any work at ~100% while all the worker and
wayland threads are at 0%.

The blocking call chain in the gdb output is:
kpView::mouseMoveEvent
-> kpAbstractSelectionTool::operationResizeScale
-> kpToolSelectionResizeScaleCommand::resizeScaleAndMove
-> kpAbstractImageSelection::setTransparency
-> kpAbstractImageSelection::recalculateTransparencyMaskCache
-> QRasterPaintEngine::drawPoints

And it happens inside the qt mouse event path: QWidgetWindow::handleMouseEvent
-> QWidget::event -> kpView::mouseMoveEvent which is why I initially assumed it
was related to mouse polling but:

None of these had any effect:
- QT_FLUSH_UPDATE=1, QT_FLUSH_PAINT=1
- QT_SCALE_FACTOR=1, QT_ENABLE_HIGHDPI_SCALING=0
- Lowering mouse polling and DPI

So now I assume it's not actually input related but related to recalculating
the transparencies and raster drawing for every resize update through
mouseMoveEvent. Are these things intended to be recalced so often during
interactive resizing (or are they being recalced with too high resolution)?

Could there be an option to disable rendering the "live previews" for
resizing/scaling as a workaround, if this is too much of a work to fix, it
would probably also make the app run better on older hardware.

Operating System: Manjaro Linux
KDE Plasma Version: 6.5.4
KDE Frameworks Version: 6.21.0
Qt Version: 6.10.1
Kernel Version: 6.18.1-1-MANJARO (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5800X3D 8-Core Processor
Memory: 128 GiB of RAM (125.4 GiB usable)
Graphics Processor: AMD Radeon RX 7900 XTX

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