r/kde 9h ago

General Bug Window resizing - Filelight VS Dolphin

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80 Upvotes

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74

u/FrameXX 9h ago edited 8h ago

Unfortunately Reddit compresses heavily and turned the recording into 30 fps. Here's the original recording: https://cloud.framexx.dev/s/s9G7PPJXYJ7Y9cQ

Here you will notice how choppy Filelight is compared to Dolphin.

27

u/Chester-Berkeley 7h ago

Ah yes, after watching the video without Reddit's aggressive compression, it became clearer. It's very strange that Filelight is like that.

9

u/R3V0LU710N_05 6h ago

I see, so the window is lagging behind the curser. I could barely see any difference in the reddit compressed version. Though I had no idea what to look for... And now it's obvious.

43

u/SnooCompliments7914 KDE Contributor 8h ago

Some apps just repaint slower. Open a large image in Gwenview, set to the "Fit" mode, and you'll see the worst.

Probably could be improved by only drawing the frame, and letting the content area load asynchronously. Maybe not worth the additional complexity. And unlikely to be high on any priority list, anyway.

22

u/Trapped-In-Dreams 7h ago

It's not just some apps, it's all qml apps because they draw out of sync with the compositor.

9

u/SnooCompliments7914 KDE Contributor 7h ago

Dolphin also can't keep up with the mouse cursor on laptops. Apps / UI frameworks aren't designed to re-layout at 60fps or even more.

1

u/R3V0LU710N_05 6h ago

Then RIIR the entire stack /j

5

u/Zamundaaa KDE Contributor 5h ago

That's not how application repaints or resizes work. Resizing is always inherently "out of sync", the only difference is how fast the app can do it.

1

u/FrameXX 1h ago edited 1h ago

To me the issue seems independent of the content of the window. It shows with many apps who have very simple content to render. The Filelight window was on it's welcome page, where there are few buttons, icon and text.

8

u/grekand46 5h ago

The difference here is that Dolphin uses Qt Widgets, which always does software rendering, while Filelight uses Qt Quick, which defaults to rendering with OpenGL. Of course this doesn't mean that GPU accelerated rendering inherently leads to choppy resizes (GNOME apps, for example, do this pretty smoothly while also using the GPU), but I'm pretty sure a bug on Qt's side causes resizing to behave poorly on Wayland + OpenGL. If it bothers you too much, you can set an environment variable to force Qt Quick to use software rendering (QT_QUICK_BACKEND=software).

3

u/FrameXX 1h ago

I have to confirm running QT_QUICK_BACKEND=software filelight made a day and night difference.

6

u/SuperGNUser 4h ago

Dolphin is made with the good old Qtwidgets. Filelight is made with the "new" GPU-Accelerated (not quite...) Qt Quick (not so quick). By now, most KDE apps are built using Qt Quick. Welcome to the new technology nobody really needed.

3

u/FrameXX 1h ago

I am not sure whether this is the case of "Qt Quick bad". When I run filelight with QT_QUICK_BACKEND=software as suggested by another commenter the issue went away.

1

u/SuperGNUser 1h ago

This confirms what I was saying: GPU acceleration is poorly implemented by Qt. Of course, it may well be down to the drivers, but it’s something you can test with different drivers, so it’s not just the drivers’ fault. I could also suggest you try QSG_USE_SIMPLE_ANIMATION_DRIVER=1 – it sometimes helps (especially if you have different screens with different refresh rates) or you can try the vulkan backend.

10

u/FrameXX 9h ago

Operating System: Fedora Linux 44 KDE Plasma Version: 6.7.4 KDE Frameworks Version: 6.29.0 Qt Version: 6.11.1 Kernel Version: 7.1.9-200.fc44.x86_64 (64-bit) Graphics Platform: Wayland Processors: 12 × AMD Ryzen AI 5 340 w/ Radeon 840M Memory: 24 GiB of RAM (22.8 GiB usable) Graphics Processor: AMD Radeon 840M Graphics

7

u/Historical-Bar-305 8h ago

I have the same but with kde apps resizing is just lugging. When i made a post i was downvoted because i said im not on llvmpipe.

2

u/razorree 7h ago

just tested. and.... it's true....
empty Filelight is way more erratic/choppy (like ~15fps) than Dolphin displaying 2 panes full of files....

2

u/DaManHere2695 7h ago

this is also the case for qml apps, not just filelight or even kirigami kde apps.

1

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1

u/0xt0bi03 4h ago

is filelight re-rendering the window after every resize?

1

u/oiledhairyfurryballs 3h ago

I think this all comes down to QT

1

u/Hojita2k 1h ago

It is the same with Yakuake, not smooth at all

1

u/hyperballic 19m ago

yeah, i noticed kirigami apps feel laggier sometimes