This makes it easier to spot syntax errors when editing the
class reference. The schema is referenced locally so validation
can still work offline.
Each class XML's schema conformance is also checked on GitHub Actions.
The CylinderMesh generation code handles this special case and
avoids generating the top and bottom faces if their radius is equal
to 0. This improves performance by reducing the number of vertices
to draw.
If both values are set to 0, nothing will be visible but the mesh
generation will still succeed.
This also improves the CylinderMesh class documentation.
(cherry picked from commit b4ed84ba2b)
We already removed it from the online docs with #35132.
Currently it can only be "Built-In Types" (Variant types) or "Core"
(everything else), which is of limited use.
We might also want to consider dropping it from `ClassDB` altogether
in Godot 4.0.
