Bug 504552

Summary:	Pressure Maxes Out at 47.4% with XP-Pen Artist 16 2nd Gen
Product:	[Applications] krita	Reporter:	_RM_ <52whitekeys>
Component:	Tablets (tablet issues are only very rarely bugs in Krita!)	Assignee:	Krita Bugs <krita-bugs-null>
Status:	REPORTED ---
Severity:	normal
Priority:	NOR
Version First Reported In:	5.2.9
Target Milestone:	---
Platform:	Ubuntu
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	Results of Steps to Reproduce View of Tablet Tester Output. Shows pressure maxing out at 47.4% Work around that I have found driver output is correct

Description _RM_ 2025-05-20 00:59:12 UTC

Created attachment 181549 [details]
Results of Steps to Reproduce

SUMMARY


STEPS TO REPRODUCE
1. Set up tablet (physical hookup, launch driver, etc)
2. Open krita
3. Select a brush with opacity controlled by pen pressure (i.e. Basic-2 Opacity)
4. Paint with the brush at full pressure


OBSERVED RESULT
The brush stroke never reaches full black. It caps out at ~50% gray at full pen pressure


EXPECTED RESULT
The opacity of the stroke should be fully opaque at full pen pressure

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Ubuntu 20.04.6 LTS 
Krita Version: 5.2.9 (installed via snap)
XP-Pen Driver Version: 4.0.7 (7c4a501)


ADDITIONAL INFORMATION
The Artist 16 is listed as "supposed to work" on the [List of Supported Tablets](https://docs.krita.org/en/reference_manual/list_supported_tablets.html#list-supported-tablets)

Tablet has 8191 levels of pressure sensitivity

I opened `Settings > Configure Krita > Tablet Settings > Open Tablet Tester` and was able to see that the pressure input was getting clipped at 47.4% (pressure level 3882)

Comment 1 _RM_ 2025-05-20 01:00:22 UTC

Created attachment 181550 [details]
View of Tablet Tester Output. Shows pressure maxing out at 47.4%

Comment 2 _RM_ 2025-05-20 01:14:17 UTC

Created attachment 181551 [details]
Work around that I have found

I can work around this bug by adjusting the global input curve, but it cuts my pressure range in half

Comment 3 _RM_ 2025-05-21 02:21:14 UTC

Created attachment 181590 [details]
driver output is correct

I used `evtest` to check the raw output of the driver and it is reporting values just fine. It is reaching its max value of 8191 (not clipping at ~3882). This indicates that the issue is likely how krita is ingesting this information.

Comment 4 _RM_ 2025-05-21 15:47:06 UTC

Documentation says that the tablet tester doesn't modify the value at all. Given that the driver is outputting the correct value and krita isn't modifying it, I believe this is a QT event issue

https://docs.krita.org/en/reference_manual/preferences/tablet_settings.html

Comment 5 _RM_ 2025-05-22 01:58:11 UTC

I have cross posted this issue with QT: https://bugreports.qt.io/browse/QTBUG-137091?filter=-2
I will wait to close this bug until someone from the krita development team chimes in