Optional per-call paint context, threaded through defaultDrawOne's third
argument. Lets a rendering entry point override ambient environment reads
— the headless renderSceneToPixels path supplies its own bitmap resolver
here so consumers reuse their own decode caches. Custom painters may
ignore it entirely.
Override bitmap resolution for image nodes. When set it is authoritative:
the global imageCache is not consulted, and an undefined result
paints the deterministic grey placeholder outline (never the ambient
load-status error variant).
Optional per-call paint context, threaded through
defaultDrawOne's third argument. Lets a rendering entry point override ambient environment reads — the headlessrenderSceneToPixelspath supplies its own bitmap resolver here so consumers reuse their own decode caches. Custom painters may ignore it entirely.