Bug 481572

Created attachment 165951 [details]
video of opening krita and drawing a line.

SUMMARY
Krita is very slow and laggy. I think it's a problem with my setup, but I don't know what.
I'm testing on krita 5.3.0-prealpha (git a707e0c), but it happens on krita 5.2.2 as well (i switched to git to see if it was fixed)
The only way I can explain is that making document or opening an existing .kra is very slow and after it opens, everything is very delayed, from pressing menu bar buttons to trying to draw a line.

STEPS TO REPRODUCE
1. Open krita
2. try to create a document or open an existing .kra
3. wait a long time
4. try to interact with krita

OBSERVED RESULT
Creating or opening a document takes a long time. Doing anything in krita after a document is open takes a long time. Resizing the window during this either doesn't work at all (like it's not responding but the window doesn't gray out) or black boxes show up like krita isn't updating the screen properly.

EXPECTED RESULT
everything works at normal speed

Operating System: Arch Linux 
KDE Plasma Version: 5.93.0
KDE Frameworks Version: 5.249.0
Qt Version: 6.7.0
Kernel Version: 6.8.0-rc4-273-tkg-eevdf (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 3700X 8-Core Processor
Memory: 31.3 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 2070 SUPER/PCIe/SSE2

ADDITIONAL INFORMATION
I've added a video. The video is pretty long with some parts with nothing happening because I'm waiting for the document to load so I move the cursor constantly to show that the video is still going.
Towards the end of the video when I move the cursor back and forth at the bottom, after creating the file, I've drawn a line on the canvas and I'm waiting for it to show up on screen.
This is the console output

> krita
> Invalid profile :  "/usr/share/color/icc/colord/Crayons.icc"
> Invalid profile :  "/usr/share/color/icc/colord/x11-colors.icc"
> krita.lib.pigment: Replacing color space factory "LABA" "L*a*b* (16-bit integer/channel, unmanaged)" with "LABA" "L*a*b*/Alpha (16-bit integer/channel)"
> krita.lib.pigment: Replacing color space factory "RGBA" "RGB (8-bit integer/channel, unmanaged)" with "RGBA" "RGB/Alpha (8-bit integer/channel)"
> krita.lib.pigment: Replacing color space factory "RGBA16" "RGB (16-bit integer/channel, unmanaged)" with "RGBA16" "RGB/Alpha (16-bit integer/channel)"
> QObject::startTimer: Timers cannot have negative intervals
> /usr/lib/krita-python-libs/krita added to PYTHONPATH
> QPainter::begin: Paint device returned engine == 0, type: 3
> QPainter::setCompositionMode: Painter not active
> QPainter::begin: Paint device returned engine == 0, type: 3
> QPainter::setCompositionMode: Painter not active
> zsh: terminated  krita