[AussieWog93]

I don't understand the technical reasons behind it, but for whatever reason doing something like resizing a Window for any non-trivial GUI seems to cause the repaints to drop down to 15-20Hz in Qt and spike the CPU usage massively. The same issue doesn't occur with Win32 or Cocoa.

[smaudet]

You probably don't have graphics drivers installed...

IIRC the fancier toolkits (Qt, GTK) do widget accell with either mandatory blitting and/or 3d (OpenGL/DirectX) (Other frameworks like WPF and Cocoa are notorious for this too).

There are, or used to be, frameworks that were not gpu dependent.

I've never hear nor seen these massive drops you claim to, so either you are running 20 year old hardware or your graphics aren't on, or you have some other hardware issue...

[jcelerier]

That's interesting, I have the exact opposite experience, I used to have a MBP dual booted with ArchLinux, and resizing windows was incredibly much smoother on Linux with either Dolphin, Nautilus or Thunar, than with Finder on the Mac which looked like it only drawed 1/5th of the frames compared to linux.

[PaulDavisThe1st]

I do understand the technical reasons behind it, and it has nothing to do with bloat. It mostly has to do with mapping a cross-platform (i.e. generic) window abstraction onto a specific OS-provided drawing/event/windowing API.

[AussieWog93]

I built my own cross-platform windowing/event API from scratch at my last job, based on top of win32 on Windows, Cocoa on Mac and Qt on Linux. The only platform where there was any noticeable performance drops at all was Linux, because it relied on Qt.

When I said "I don't understand the technical reasons behind it", I didn't mean "I don't understand how to abstract OS-native APIs". I meant "I don't understand how a team of intelligent people managed to fuck things up this badly".

[renox]

I'm not it's a Qt issue: it could be a lack of hardware acceleration on Linux's GPU driver..

[AussieWog93]

This is something I've observed cross-platform (Windows, macOS and Linux) across both nVidia and AMD machines with updated drivers. Actually try it.

Get your favourite Qt program, resize the window like a madman and watch your CPU usage launch into the stratosphere.

[smaudet]

There are some reports of bad things happening with inefficient QPainter usage, and some bugs related to text drawing especially after qt5, after a cursory look...would be better to provide specific examples. I do rather suspect something machine or even program specific, though.