library-mesh

The shared "instantiate a model from a <tosi-b3d-library>" loader. One implementation, used by b3d-prop and b3d-destroyable.

Why it is shared rather than copied

It was copied first, and the copy was the problem. Three bugs arrived against the one in b3d-destroyable — rotation dropped, no scale, and a node orphaned when the element was removed mid-load (#47/#48/#49) — and a second element with its own copy would have inherited all three, silently, because a fix in one place cannot reach a policy that was duplicated.

That is not hypothetical here: the panel-sizing formula in this repo was copied to three sites, fixed in one, and the two survivors were found by a review rather than by anything failing.

⚠️ And sharing the loader was not sufficient. b3d-turret and b3d-launcher both called THIS function and still dropped rotation, because transform's rotation fields were optional — so the shared implementation was correct and two of its four callers were not. A pre-release review found it. The fields are required now, which is what actually closes the seam: a shared implementation only helps where the type makes the mistake unspellable.

b3d-aircraft.loadFromLibrary is still a separate, older loader. It is NOT the same bug: an aircraft's attitude comes from the flight model every frame (fly-by-wire writes rotationQuaternion in _update), so authored rx/ry/rz could not survive on it whatever the loader did — a flying craft is oriented by flight, not by an attribute. What it does still lack is scale, a bounded wait and a missing-library error; those are in DECISIONS.md under "aircraft library loader", and its library-changed listener is now removed on disposal rather than only on success.

What it handles, and why each part exists

• The library may connect AFTER the element. Declaration order in a scene is the author's business, not a load-order contract, so it retries briefly rather than resolving once.
• Rotation is passed to instantiate, not left to a later render. AbstractMesh.render() does sync rx/ry/rz, but it is a COMPONENT render and has already run by the time an async load assigns the mesh — so position applied and rotation silently did not (#48).
• A stale load must not land. Remove the element inside the load window and the disconnect handler finds nothing to dispose, then the pending callback builds a node owned by nobody — a permanent ghost. Guarded with the caller's loadGeneration, which AbstractMesh bumps on sceneDispose (#49).