Bug 516442

Summary: Wacom tablet always shows 3 buttons even if fewer are supported
Product: [Applications] systemsettings Reporter: Kat Pavlu <realkpavel>
Component: kcm_tabletAssignee: Plasma Bugs List <plasma-bugs-null>
Status: RESOLVED FIXED    
Severity: normal CC: aleixpol, josh, nate
Priority: NOR Keywords: regression
Version First Reported In: 6.6.0   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: https://invent.kde.org/plasma/plasma-desktop/-/commit/fbed2cb25a460e4d6dd2c85b69330b60e5cac76a Version Fixed/Implemented In: 6.6.1
Sentry Crash Report:
Attachments: libwacom-list-local-devices output
patch for the bug (not yet tested)

Description Kat Pavlu 2026-02-21 07:31:52 UTC 
Created attachment 189907 [details]
libwacom-list-local-devices output

SUMMARY
I have a Thinkbook 14s Yoga. All the pens supported for this model in libwacom only have one button (see attachment). PLasma used to correctly show one button in the KCM until 6.5.4, but now it always shows 3 buttons.

I have taken a look at the logs and code listings and I think this is a regression introduced by https://invent.kde.org/plasma/plasma-desktop/-/commit/b1c4cf7b11a9f320709246a47056542ac8093a46. If I understand the code correctly, the newly introduced logic now effectively does 
numButtons = max( (numButtons on any stylus),  3). 

Included is a patched kcmtablet.cpp, where the logic is changed to:
numButtons = tabletSupported? max(numButtons on any stulys), 3

which is what I think was intended here.
I can try getting a second drive and buiding this to test it .

STEPS TO REPRODUCE
1. Open the Drawing Tablet KCM on a Lenovo Yoga device

Operating System: Fedora Linux 43
KDE Plasma Version: 6.6.0
KDE Frameworks Version: 6.23.0
Qt Version: 6.10.1
Kernel Version: 6.18.12-200.fc43.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 8 × 11th Gen Intel® Core™ i7-1165G7 @ 2.80GHz
Memory: 16 GiB of RAM (15.4 GiB usable)
Graphics Processor: Intel® Iris® Xe Graphics
Manufacturer: LENOVO
Product Name: 20WE
System Version: ThinkBook 14s Yoga ITL
Comment 1 Kat Pavlu 2026-02-21 07:32:23 UTC 
Created attachment 189908 [details]
patch for the bug (not yet tested)
Comment 2 Bug Janitor Service 2026-02-22 20:34:08 UTC 
A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-desktop/-/merge_requests/3567
Comment 3 Joshua Goins 2026-02-23 21:21:16 UTC 
Git commit fbed2cb25a460e4d6dd2c85b69330b60e5cac76a by Joshua Goins, on behalf of Kat Pavlu.
Committed on 23/02/2026 at 21:21.
Pushed by redstrate into branch 'master'.

kcms/tablet: Stop showing non existent buttons

Prevents the Tablet kcm from always showing 3 buttons on a pen if all supported pens have fewer than that.

M  +1    -0    kcms/tablet/kcmtablet.cpp

https://invent.kde.org/plasma/plasma-desktop/-/commit/fbed2cb25a460e4d6dd2c85b69330b60e5cac76a