Bug 510978

Summary:	Windows don't snap correctly
Product:	[Plasma] kwin	Reporter:	monnety
Component:	general	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	NEEDSINFO WAITINGFORINFO
Severity:	minor	CC:	kwin-bugs-null, nate, uhhadd
Priority:	NOR	Keywords:	regression
Version First Reported In:	6.5.0
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description monnety 2025-10-23 20:52:25 UTC

SUMMARY

I use KDE Neon with the dark Breeze theme and Plasma just was updated to version 6.5. Now the following problem appeared.

STEPS TO REPRODUCE
1. Window Management -> Window Behavior -> Enable "Snap windows only when overlapping"
2. Move a window towards another window or lthe eft/right-hand screen edge.

OBSERVED RESULT

The window doesn't snap perfectly because its white border doesn't display anymore (one pixel too wide).
See my screen recordings :
- https://jumpshare.com/s/QBfOKDmx6zVKmhnUOZ0w
- https://jumpshare.com/s/AiZKXYEthUsrikws1CfK

EXPECTED RESULT

The window should snap pixel-perfectly. It was the case in the previous versions. 

SOFTWARE/OS VERSIONS
Operating System: KDE neon User Edition
KDE Plasma Version: 6.5.0
KDE Frameworks Version: 6.19.0
Qt Version: 6.9.2
Kernel Version: 6.14.0-33-generic (64-bit)
Graphics Platform: Wayland

ADDITIONAL INFORMATION

Is there any config file I can edit to solve this problem on my computer until the bug is patched ?

Comment 1 monnety 2025-10-23 20:59:42 UTC

The same problem happens when maximizing the window.

Comment 2 Nate Graham 2025-10-24 17:30:20 UTC

So you're saying that snapped windows now overlap the thing they're snapped to by one pixel? So I have that right?

Is it also the case for you when *not* using the "Snap windows only when overlapping" setting?

Comment 3 monnety 2025-10-24 19:02:51 UTC

(In reply to Nate Graham from comment #2)
> So you're saying that snapped windows now overlap the thing they're snapped
> to by one pixel? So I have that right?

Hello and thank you for your reply. Yes, you're right, it's overlapping by one pixel. In the previous versions the overlapping didn't occur.

> Is it also the case for you when *not* using the "Snap windows only when
> overlapping" setting?

Well, my mistake, sorry. The behavior I have described above occurs when this setting is disabled. But the same happens when it is enabled : one pixel overlapping between the windows.

The snapping works perfectly on older versions. I have just tested it on Distrosea (https://distrosea.com/fr/start/kdeneon-user-default/) with KDE Neon 6.2 (using Plasma 6.2.5).  

I hope it helps.

Comment 4 Vlad Zahorodnii 2025-10-25 09:07:09 UTC

In 6.4 and prior versions, the outline was implemented as a normal window border, that's probably the reason why the behavior is different in 6.5.