Why is the `VRServiceCreator` API needed?

[servo]

Why is the `VRServiceCreator` API needed?

[asajeffrey]

In particular, for services that take ownership of some parameters, the VRServiceCreator API is not ideal:

let foo_creator = FooServiceCreator::new(this, that);
let foo1 = foo_creator.new_service(); // foo1 now owns this and that
let foo2 = foo_creator.new_service(); // What happens now? panic?

[jdm]

The only reason I can see for its existence is for this code, but it's not clear to me that that abstraction is necessary.

[asajeffrey]

Indeed, why not keep an array of VRService objects rather than VRServiceCreator objects?

[MortimerGoro]

It's used to register services based on cargo features and in order to do lazy initialization (only initialize services when first requested from JavaScript thread, otherwise some system UI may trigger (e.g Steam VR state UI on HTC Vive).

I think we could switch to a VRService array as long as we mantain a lazy initialization

[asajeffrey]

The VRService doesn't need to do any initialization until initialize is called, which won't happen until JS fetches the displays or gamepads.