ReadonlybackendWhich §62 backend this builds. One registration per backend per registry.
Constructs the backend. Must not initialize it — the registry calls Renderer.initialize itself, because §62's fallback is defined in terms of initialization failing.
Optionaloptions: RendererOptionsA cheap, side-effect-free answer to "could this environment run this backend at all?" (§62 capability tiers).
This is a pre-filter, not the real gate: the real gate is
Renderer.initialize, which is the only code that can tell a blocked
GPU from a working one, and whose failure "auto" already recovers from by
moving to the next backend. So a probe must not acquire a context, must not
allocate a device, and above all must not touch the caller's canvas — a
canvas hands out one context per type, so a probe that called
getContext("webgl2") with its own attributes would silently fix the
attributes of the context the backend later acquires.
Answering true optimistically is safe (initialization decides);
answering false is a promise that trying would be pointless.
Optionaloptions: RendererOptions
One backend's entry in a RendererRegistry — everything the registry needs to decide whether to try it, and how to build it.