Unable to set background image of O3DVisualizer

[Fraer]

Checklist

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

Describe the issue

I would like to show a background image when using O3DVisualizer.

Steps to reproduce the bug

import open3d as o3d
import open3d.visualization.gui as gui
import open3d.visualization.rendering as rendering

gui.Application.instance.initialize()
window = o3d.visualization.O3DVisualizer("ModernUI")

juneau_data = o3d.data.JuneauImage()
img = o3d.io.read_image(juneau_data.path)

window.set_background([1, 1, 1, 1], img)

gui.Application.instance.add_window(window)
gui.Application.instance.run()
gui.Application.instance.quit()

Error message

No response

Expected behavior

The background image should be visible when the application is running.

Open3D, Python and System information

- Operating system: macOS 14.5
- Python version: 3.11.9 (main, Apr  2 2024, 08:25:04) [Clang 15.0.0 (clang-1500.3.9.4)]
- Open3D version: output from python: 0.18.0+90810a335
- System architecture: x86
- Is this a remote workstation?: no
- How did you install Open3D?: build from source
- Compiler version (if built from source): Clang 15.0.0

Additional information

[Fraer]

ok it works by explicitly removing skybox 😅

window.show_skybox(False)

[Fraer]

would be nice to show a warning when set_background is called but the skybox is enabled