Bug 495505

Created attachment 175317 [details]
A short video demonstrating the file selection and highlighting bug.

SUMMARY
Selecting or highlighting files/folders in the Desktop view spikes CPU usage; rapidly highlighting/selecting causes lag dependent on the amount of visible files in the Desktop folder.

STEPS TO REPRODUCE
1. Create any amount of files or folders in the Desktop folder.
2. Rapidly move your mouse back and forth over these files/folders, observing CPU usage via a program such as htop.

OBSERVED RESULT
Selecting or highlighting any amount of files will lead to an abnormal spike in CPU usage. If the user has many files or folders visible on their Desktop (16+ in my case), this spike will accompanied by lag/throttling.
CPU usage seems to be at least partially dependent on the number of files and folders in the Desktop folder.

EXPECTED RESULT
No lag, low CPU usage.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux 
KDE Plasma Version: 6.2.2
KDE Frameworks Version: 6.7.0
Qt Version: 6.8.0

ADDITIONAL INFORMATION
This issue seems related to https://bugs.kde.org/show_bug.cgi?id=493376, but is file-agnostic and only appeared (for me) after updating to Plasma 6.2, whereas the bug reporter was using Plasma 6.1.5.

I've also experimented with non-dummy files, including a mix of txt, pdf, and odt, as well as a desktop only comprising of '.desktop' files. It seems that the number of visible files is the primary factor behind this bug, rather than file or metadata size, though the latter may still be a contributing factor (see https://bugs.kde.org/show_bug.cgi?id=489894)

Kernel Version: 6.11.5-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 12 × 11th Gen Intel® Core™ i5-11400 @ 2.60GHz
Graphics Processor: AMD Radeon RX 6800 [Mesa 24.2.5]