Qt bug on macOS: high CPU usage when scrolling library

[foss-]

Bug Description

This is a long time problem in Qt on macOS: When scrolling the library up and down continuously, CPU usage goes to 99 %:

100 % reproducible.

macOS 13.6.5
Mixxx 2.5-alpha-255-g2d2d5f304b (main)
Qt 6.5.3

This is not a new problem, it has been going on for as long Mixxx was available on macOS. This needs to be resolved in Qt, but it is fair to have this issue in the Mixxx repo, to keep track of things.

Open
https://bugreports.qt.io/browse/QTBUG-123343 reported against 6.6.2

Resolved
https://bugreports.qt.io/browse/QTBUG-73117 resolved 2022-06-14 6.4, 6.3, 6.2

Other software affected by the bug: strawberrymusicplayer/strawberry#542 (comment)

Version

any

OS

macOS 13.6.5

[ronso0]

Dupe of your own report #11603 ?

Some questions came to mind before I discovered #11603:
Please clarify:
does it occur when
a) scrolling by dragging the scrollbars
b) moving the track selection with Up/Down keys (or with [Libary],MoveUp/Down
c) regardless of a/b if the cover column AND library cover art (in the sidebar) are hidden

If it's the b), increasing the track select delay as proposed in #12881 would at least be valid workaround until someone has a solution for the root cause.

[foss-]

#11603 is probably another symptom of the same problem.

So since the description here is more accurate and 11603 only describes a symptom I'd rather set #11603 to duplicate of this issue here.

a) also happens when dragging scrollbar
b) using arrow keys also puts the CPU at 101 %
c) even with cover art in left bottom and library column not showing when scrolling via mouse, scrollbar or arrow keys, CPU goes to 100 %

[m0dB]

Can you try if this makes a difference?

https://github.com/m0dB/mixxx/tree/no-elide

[foss-]

Sorry for the very late reply, was overwhelmed with work and life. Could you link a build to test or instruct where to find a testable build?