[kwin] [Bug 523854] New: Middle mouse drag becomes constrained to one axis in multiple applications on Wayland

https://bugs.kde.org/show_bug.cgi?id=3D523854

            Bug ID: 523854
           Summary: Middle mouse drag becomes constrained to one axis in
                    multiple applications on Wayland
    Classification: Plasma
           Product: kwin
      Version First 6.6.5
       Reported In:
          Platform: Kubuntu
                OS: Linux
            Status: REPORTED
          Severity: minor
          Priority: NOR
         Component: wayland-generic
          Assignee: [email protected]
          Reporter: [email protected]
  Target Milestone: ---

Created attachment 194846
  --> https://bugs.kde.org/attachment.cgi?id=3D194846&action=3Dedit
This is the evtest I did to show me moving the mouse diagonally and it pick=
ing
it up successfully. Ignore the 8bit controller before, I've unplugged that =
and
this bug still occurs.

DESCRIPTION
You can try this in either Blender or GIMP. When you middle-click and drag =
it
is suppose to pan the view but instead the drag becomes constrained to the
initial horizontal or vertical axis, depending on the direction of the first
movement.
I can break out of this "axis lock" when I wiggle the mouse around wildly
enough, but the moment I let go of the middle-mouse and try again, it happe=
ns
once more.

I've disabled Mouse Acceleration.=20
evtest reports normal REL_X and REL_Y motion while the issue occurs.
libinput list-devices reports the mouse normally.
Disconnecting my Huion Kamvas Pro 12 tablet does not change the behavior.
Disconnecting other USB input devices does not change the behavior.
No input remapping software (ydotool, xdotool, input-remapper, etc.) is
running.

Softwares I've tested this in:
Blender 5.3 Alpha (official build)
Blender 5.2 LTS (Flatpak)
GIMP 3.3 (Flatpak)

STEPS TO REPRODUCE
1. Open Blender and at the "New File" section on the welcome screen, click
"General.
2. In the 3D view port, hold middle-mouse and drag around and take note of =
the
axis lock.

OBSERVED RESULT
Holding the middle mouse button and dragging causes movement to become
constrained to either the horizontal or vertical axis. Rapidly wiggling the
mouse temporarily restores free diagonal movement.

EXPECTED RESULT
Holding the middle mouse button and dragging should allow smooth, unrestric=
ted
movement in both X and Y directions without any axis constraint.

SOFTWARE/OS VERSIONS
Operating System: Kubuntu 26.04 LTS
KDE Plasma Version: 6.6.5
KDE Frameworks Version: 6.24.0
Qt Version: 6.10.2

ADDITIONAL INFORMATION
My mouse is:  Steel Series Rival 3

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