Bug 507501

Summary: Implement a less demanding fake blur for lower powered systems so themes are still readable
Product: [Plasma] kwin Reporter: Ellie <el>
Component: auroraeAssignee: KWin default assignee <kwin-bugs-null>
Status: CONFIRMED ---    
Severity: wishlist CC: kdedev
Priority: NOR    
Version First Reported In: 6.4.2   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Ellie 2025-07-26 04:43:13 UTC 
SUMMARY

On some devices like the Raspberry Pi 5, the blur seems to be a too demanding effect that leads to extreme lag. However, some themes that use blur seem not prepared to handle it well if it's disabled, leading e.g. to impossible to read text in title bars. It would therefore be nice if there was an alternative blur implementation that was less demanding, based on e.g. pre-blurring the desktop wallpaper as a static texture and then simply showing parts of that pre-blurred texture for the blurred areas.

STEPS TO REPRODUCE

1. Use Raspberry Pi 5
2. Enable blur effects for transparent window decoration parts
3. See that it lags and there's no way to have some sort of blur-like alternative effect that is fast

OBSERVED RESULT

Built-in blur is very demanding on some hardware, there doesn't seem to be some "low demand blur" which would be nice

EXPECTED RESULT

It would be nice to have some alternate blur variant that is less accurate (by e.g. just blurring the wallpaper) and less demanding.

SOFTWARE/OS VERSIONS

Windows: 
macOS: 
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: 
KDE Plasma Version: 6.4.2
KDE Frameworks Version: 6.16.0
Qt Version: 6.9.1

ADDITIONAL INFORMATION
Comment 1 TraceyC 2025-07-30 15:28:52 UTC 
This seems like a bug trying to be fixed by a new feature. The core problem seems to be in the performance of blur, and that some themes don't have good readability with it being turned off.

A less demanding blur option might be the first step in solving the overall problem. I'll let the developers weigh in.
Comment 2 Ellie 2025-07-30 15:31:19 UTC 
Oh, good point, it's true that if you could keep the blur as-is and make it faster, I wouldn't complain. I simply assumed given how bad the GPU of the Raspberry PI is, that a simpler blur might be needed, but I don't think anybody's going to mind the fully functional version if it's feasible. Sorry if I'm not making a lot of sense.
Comment 3 TraceyC 2025-07-30 16:56:17 UTC 
.