'Camera.unproject' does not work properly under KDE-Plasma/Wayland with XDG_SESSION_TYPE=x11

Checklist

• I have searched for similar issues.
• For Python issues, I have tested with the latest development wheel.
• I have checked the release documentation and the latest documentation (for main branch).

Describe the issue

The open3d.visualization.rendering.Camera.unproject method as demonstrated in the example file "open3d/examples/visualization/mouse_and_point_coord.py" does not work properly when running with XDG_SESSION_TYPE=x11 under KDE-Plasma/Wayland.

When you Ctrl-click on a point of the point cloud the first time, some coordinates are displayed which are incorrect. Every other Ctrl-click on any other point of the point cloud returns exactly the same coordinates. After zooming or rotating the scene a Ctrl-click does again display different coordinate values. However, again selecting any other point with Ctrl-click displays the same coordinates until you change the view of the scene again.

Steps to reproduce the bug

export XDG_SESSION_TYPE=x11

python site-packages/open3d/examples/visualization/mouse_and_point_coord.py

Error message

No error message.

Expected behavior

On Ctrl-click the proper coordinates of the selected point should be displayed.

Open3D, Python and System information

- Operating system: ArchLinux with KDE-Plasma/Wayland
- Python version: Python 3.14.3
- Open3D version: 0.19.0
- System architecture: x86
- Is this a remote workstation?: no
- How did you install Open3D?: pip
- Compiler version (if built from source):

Additional information

Is it planned to natively support Wayland sometime in the near future?