Bug 502103

Summary:	Special cursors (Eraser, Brush) and selection borders leave behind visual artifacts until the window is scrolled, resized or redrawn when fractional scaling is used
Product:	[Applications] kolourpaint	Reporter:	iodreamify
Component:	general	Assignee:	kolourpaint-support
Status:	CONFIRMED ---
Severity:	normal	CC:	grazynapp65, john.kizer, nate, Ole.Urdland91
Priority:	NOR	Keywords:	wayland-only
Version First Reported In:	24.12.3
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
See Also:	https://bugs.kde.org/show_bug.cgi?id=491562 https://bugs.kde.org/show_bug.cgi?id=499289 https://bugs.kde.org/show_bug.cgi?id=502322
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	kolourpaint glitches konsole text glitches

Description iodreamify 2025-03-28 02:19:57 UTC

Created attachment 179802 [details]
kolourpaint glitches

SUMMARY
I'm getting various graphics glitches with 1.25x scaling (or any fractional scaling factor inbetween 100-200%) 

One symptom is in kolourpaint if i use the selection tool to select something and then shrink back the rectangle(see screenshot) . If i open kolourpaint in xwayland mode with "Legacy X11 applications = scaled by the system" the bug is there. But with "apply scaling themselves" bug is gone.

This also happens with Pinta but curiously does not happen with Gimp or Drawing. 

The other one is with coloured text characters in konsole. Originally reported  here but with no resolution and i assume they're related: https://bugs.kde.org/show_bug.cgi?id=491562 Similar x11 behavior as with kolourpaint.  

Possibly related: https://bugs.kde.org/show_bug.cgi?id=466373

STEPS TO REPRODUCE
1. set fractional scaling to 1.25 
2. open kolourpaint 
3. drag a selection with selection tool and shrink it

OBSERVED RESULT
visual artifacts

EXPECTED RESULT
no visual artifacts

Operating System: Arch Linux 
KDE Plasma Version: 6.3.3
KDE Frameworks Version: 6.12.0
Qt Version: 6.8.2
Kernel Version: 6.13.8-arch1-1 (64-bit)
Graphics Platform: Wayland
Graphics Processor 1: AMD Radeon 660M
Product Name: ASUS TUF Gaming A15 FA507NU_FA507NU

Comment 1 iodreamify 2025-03-28 02:22:44 UTC

Created attachment 179804 [details]
konsole text glitches

Comment 2 iodreamify 2025-03-28 02:32:16 UTC

Oh and forgot to mention in all cases the glitch disappears if i resize the window a tiny bit or force it to redraw.

Comment 3 Nate Graham 2025-03-28 23:00:08 UTC

> If i open kolourpaint in xwayland mode with "Legacy X11 applications = scaled by the system" the bug is there

This isn't really supported or recommended; why are you forcing Kolourpaint into XWayland mode? It has native Wayland support so that should be used instead. If it works as a native Wayland app, isn't that preferable to use?

Comment 4 iodreamify 2025-03-28 23:04:29 UTC

(In reply to Nate Graham from comment #3)
> > If i open kolourpaint in xwayland mode with "Legacy X11 applications = scaled by the system" the bug is there
> 
> This isn't really supported or recommended; why are you forcing Kolourpaint
> into XWayland mode? It has native Wayland support so that should be used
> instead. If it works as a native Wayland app, isn't that preferable to use?

Sorry for the confusion, I only mentioned the xwayland tests because i thought that might help track down the bug because i noticed the bug was also happening there alongside the default Wayland code path. I do not usually use apps in xwayland mode if they support Wayland.

Comment 5 iodreamify 2025-03-28 23:06:58 UTC

The title to this bug incorrect now because these glitches happen mainly in Wayland mode, not in xwayland. The Xwayland stuff i mentioned was in addition to this and may be disregarded if it's not helpful.

Comment 6 Nate Graham 2025-03-31 16:14:29 UTC

Gotcha, thanks.

These look like app-specific issues; let's track Kolourpaint here. Can you open a new bug report about Konsole, and put it in the "see also" field of this one? Thanks!

Comment 7 John Kizer 2025-04-13 04:41:11 UTC

I can reproduce on my system below:

Operating System: Fedora Linux 41
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.12.0
Qt Version: 6.8.2
Kernel Version: 6.13.10-200.fc41.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 7800X3D 8-Core Processor
Memory: 30.4 GiB of RAM
Graphics Processor 1: NVIDIA GeForce RTX 4070 SUPER

Comment 8 John Kizer 2025-06-15 23:04:02 UTC

*** Bug 505150 has been marked as a duplicate of this bug. ***

Comment 9 grazynapp65 2025-10-12 12:43:15 UTC

It's also happening to me on Gnome (only happens with Gnome's fractional scaling)

Operating System: Ubuntu 25.04
KDE Plasma Version:
KDE Frameworks Version: 
Qt Version: 
Kernel Version: 6.14.0-33-generic
Graphics Platform: Wayland
Processors: 13th Gen Intel(R) Core(TM) i3-1315U
Memory: 16GB
Graphics Processor 1: Intel Corporation Raptor Lake-P [UHD Graphics] (Kernel driver: i915)