`EditorNode3DGizmo::add_collision_triangles` replaces previous meshes instead of adding

[juanjp600]

Tested versions

Reproducible in: 4.3.beta [0918fd2], 4.2.2.stable, 4.1.4.stable

System information

Windows 10 - Godot v4.2.2.stable

Issue description

I'm playing around with the plugin system, and I wanted to add a gizmo that has collision triangles. A gizmo that needs to add collision triangles will not work correctly if it's working with multiple TriangleMeshes: only the last one added is checked for collision.

The implementation of EditorNode3DGizmo::add_collision_triangles seems to be the culprit: https://github.com/godotengine/godot/blob/ff8a2780ee777c2456ce42368e1065774c7c4c3f/editor/plugins/node_3d_editor_gizmos.cpp#L361-L363

I consider this a bug because it is inconsistent with the way other functions, like add_mesh and add_collision_segment, work.

Steps to reproduce

• Download the MRP included in this issue
• Open Scene.tscn
• Select the pyramid
• Click on the bottom triangle of the pyramid. Observe that it will not be deselected.
• Click on other triangles of the pyramid. This time, the pyramid will incorrectly be deselected.

Minimal reproduction project (MRP)

Editor3DNodeGizmo AddCollisionTriangles MRP.zip

[jsjtxietian]

I have an idea of fixing this, I'll make a pr later