[krita] [Bug 523864] New: Stylus cannot start strokes on GNOME/Wayland unless XWayla nd is bypassed (QT_QPA_PLATFORM=wayland) — no tip-down event received

https://bugs.kde.org/show_bug.cgi?id=3D523864

            Bug ID: 523864
           Summary: Stylus cannot start strokes on GNOME/Wayland unless
                    XWayland is bypassed  (QT_QPA_PLATFORM=3Dwayland) =E2=
=80=94 no
                    tip-down event received
    Classification: Applications
           Product: krita
      Version First 5.3.3
       Reported In:
          Platform: Ubuntu
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: Tablets (tablet issues are only very rarely bugs in
                    Krita!)
          Assignee: [email protected]
          Reporter: [email protected]
  Target Milestone: ---

SUMMARY
On GNOME/Wayland, Krita picks up stylus motion and pressure through=20
XWayland, but never gets a tip-down/press event =E2=80=94 so you can move t=
he=20
cursor with the pen, but can't actually start a stroke. Forcing native=20
Wayland with QT_QPA_PLATFORM=3Dwayland fixes it completely. This looks like=
=20
the same XWayland-default issue discussed in bug 379174, but that report=20
is 9 years old and covers several different symptoms (Art Pen rotation,=20
general tablet support, etc.), so I'm filing this separately with a=20
focused, easily reproducible case.

STEPS TO REPRODUCE
1. Run a GNOME/Wayland session (Ubuntu 26.04 =E2=80=94 note that the GNOME-=
on-Xorg=20
   session doesn't exist anymore on this release).
2. Launch Krita normally.
3. Touch the tablet with the stylus and try to draw on a canvas.

OBSERVED RESULT
- The cursor stays a normal system arrow instead of switching to Krita's=20
  brush cursor.
- Tablet Tester shows no tablet events at all when drawing with the=20
  stylus alone.
- The stylus moves the cursor fine, but can't start a stroke.
- Workaround I found: if I hold down the left mouse button first, and=20
  then touch the tablet with the stylus, Krita immediately starts drawing=20
  with full pressure sensitivity. Releasing the mouse button stops the=20
  stroke right away. This suggests Krita is receiving motion and pressure=20
  from the stylus via XWayland, but not a proper tip-down event, unless a=20
  real mouse button is already held down.

EXPECTED RESULT
The stylus alone should be able to start and end strokes, same as it does=20
in other applications on the same machine.

SOFTWARE/OS VERSIONS
- Ubuntu 26.04 LTS, GNOME (Wayland-only; GNOME-on-Xorg was removed=20
  upstream starting with GNOME 49)
- Reproduced on Krita 5.3.3 (AppImage), Krita 5.2.x (Snap), Krita 6.0=20
  (stable), and Krita 6 Beta =E2=80=94 so this isn't tied to one specific v=
ersion
- Tablet: XP-Pen Deco 01 v2, USB ID 28bd:0002
- evtest confirms the kernel sees everything correctly (BTN_TOUCH,=20
  ABS_PRESSURE, ABS_X/Y, tilt)
- The vendor's own XP-Pen driver test area receives stylus input just=20
  fine, and Xournal++ handles the same stylus correctly out of the box =E2=
=80=94=20
  so the tablet, driver, and kernel side all seem fine

ADDITIONAL INFORMATION
Running `QT_QPA_PLATFORM=3Dwayland krita` fixes the issue completely for=20
me =E2=80=94 tablet cursor shows up, Tablet Tester picks up events, and dra=
wing=20
works with full pressure, no need to hold the mouse button anymore.

This lines up with a June 2026 comment on bug 379174 from a Wacom rep,=20
who ran into the same XWayland-default root cause (in their case it broke=20
Art Pen rotation) and used the same fix.

Since Ubuntu 26.04 (and other GNOME 49+ distros) dropped the=20
GNOME-on-Xorg session entirely, "just switch to Xorg" isn't really an=20
option for GNOME users anymore, which makes proper native Wayland tablet=20
support more important going forward.

Would it make sense for Krita to default to QT_QPA_PLATFORM=3Dwayland on=20
Wayland sessions where the native Qt Wayland plugin is available, instead=20
of defaulting to XWayland?

SEE ALSO
https://bugs.kde.org/show_bug.cgi?id=3D379174

--=20
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