GUI in 3D demo not working when when Run On Separate Thread is checked

[IvailoBurov]

Which demo project is affected:

https://github.com/godotengine/godot-demo-projects/tree/master/viewport/gui_in_3d

OS/device including version:

Windows 10, NVIDIA GeForce RTX 3070

Issue description:

When "Run On Separate Thread" project option is checked for Physics 3D a null result is returned at line 128 for get_world_3d().direct_space_state.

Screenshots of issue:

[Calinou]

As per the description of World3D.direct_space_state:

Direct access to the world's physics 3D space state. Used for querying current and potential collisions. When using multi-threaded physics, access is limited to [method Node._physics_process] in the main thread.

find_mouse() should be called in _physics_process() to resolve this.

[Sauermann]

I believe, that this gets fixed by #925, which rewrites the demo and removes the find_mouse() call.

[Sauermann]

Haven't tested it, but based on the description, I believe, that with #925 merged, this can now be closed.

[Calinou]

As of 4.2.1, I can confirm the demo works when Run on Separate Thread is enabled for both 2D and 3D physics since #925 was merged.