Bug 511542

Summary:	[HUION] Drawing on the canvas slows down significantly with Huion Inspiroy H640P
Product:	[Applications] kolourpaint	Reporter:	Hazel <hazel-misc-accs2>
Component:	general	Assignee:	kolourpaint-support
Status:	REPORTED ---
Severity:	normal
Priority:	NOR
Version First Reported In:	25.08.2
Target Milestone:	---
Platform:	Mint (Ubuntu based)
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Hazel 2025-11-02 20:06:35 UTC

Drawing on the canvas slows down significantly with Huion Inspiroy H640P. This does not occur for the first handful of brush strokes, but over time the pointer, regardless of what tool is selected, slows down significantly and drifts all over the canvas, to the point of unusability. This happens even with the Huion driver program closed, but this does not happen with the mouse. As well, this happens regardless of how much load is on the CPU and memory, so it does not seem to be performance related.

STEPS TO REPRODUCE
1. Open KolourPaint with the Huion Inspiroy H640P connected
2. Select any brush
3. Draw on the canvas for a few dozen brush strokes until pointer becomes slow and laggy
Note: This bug occurs most reliably in slightly larger canvas sizes, 1000x1000 or higher. Replication is most consistent at 1200x1200 (my canvas sizes are usually higher than 1000x1000)

OBSERVED RESULT
Pointer gradually becomes slower and slower until it takes several seconds for it to move from one side of the canvas to the other.

EXPECTED RESULT
Pointer should be smooth and lag-free.

SOLUTIONS TRIED
- Restart KolourPaint (only resets the bug)
- Reinstall KolourPaint
- Reinstall Huion drivers
- Draw without drivers enabled (raw input)
- Draw with all other programs closed
- Draw with smaller canvas sizes (this does fix the issue somewhat, becomes more reliable of a fix the smaller the canvas. However, I regularly draw at canvas sizes 1000x1000 or larger, so this is not a good solution for me)

ADDITIONAL NOTES
- This is a problem that has gotten worse over time. It was rare when I first installed and used KolourPaint, now it is consistent and unavoidable.
- The pointer does not slow down when on the toolbars, this bug is restricted purely to the canvas.

SOFTWARE/OS VERSIONS
KolourPaint version: 25.08.2 (both repo and Flatpak versions were tested)
OS: Linux Mint 22.2 x86_64
DE: Cinnamon 6.4.8
Kernel: 6.14.0-34-generic
Shell: bash 5.2.21
Resolution: 1920x1080

HARDWARE
Device: Aspire A515-55 V1.13
Mouse: Razer DeathAdder Essential