[3.x] Make CollisionShape selection box use shape AABB

[timothyqiu]

The orange selection box is always shown for Spatial nodes in 3.x.

A CollisionShape is not a VisualInstance so it does not have a AABB itself, and the editor used a fixed fallback AABB. This can produce unexpected selection box for ancestor nodes.

This PR makes use of the shape's AABB. When no shape is assigned, it still falls back to the fixed size AABB.

Before	After

[lawnjelly]

Thought I recognised the call and indeed I added get_fallback_gizmo_aabb() for the occluders as there was no way of handling non-visual instances in the editor.

This is a good use imo, agree about the comment about the const_cast and mutable data, how big a bag of worms that would be to do I don't know.

Would this also be worth doing in 4.x? If so, you may need to include the machinery for get_fallback_gizmo_aabb() as it was only included for geometric occluders (which aren't in 4.x), but it's only a few lines if I remember right.

[timothyqiu]

Would this also be worth doing in 4.x? If so, you may need to include the machinery for get_fallback_gizmo_aabb() as it was only included for geometric occluders (which aren't in 4.x), but it's only a few lines if I remember right.

I thought the orange box for non-visual instances was intentionally removed on 4.x 😅 But some nodes do look better without the box, e.g. Camera3D and GridMap. We can probably make the box optional by returning an empty AABB in get_fallback_gizmo_aabb()?

[lawnjelly]

I thought the orange box for non-visual instances was intentionally removed on 4.x sweat_smile But some nodes do look better without the box, e.g. Camera3D and GridMap. We can probably make the box optional by returning an empty AABB in get_fallback_gizmo_aabb()?

Yup sure that could work.

Another alternative I considered at the time was moving the get_aabb() function from VisualInstance to Spatial, and have it return a default empty AABB. That would remove the need for the specific function for non-visual instances.

As far as I remember I didn't attempt this at the time just because I didn't want to change too much in 3.x, but it might be worth considering for 4.x. I'm sure this would come up as a possibility in review for a 4.x PR.

[akien-mga]

Thanks!