Processing requirements for bgColor and linked canvas/scenes

[azaroth42]

If a child scene is annotated into a parent scene, and the child has backgroundColor, accompanyingCanvas or placeholderCanvas set, then the specification should be explicit as to the processing of these properties. This becomes more problematic when multiple such children are annotated into the parent scene.

Should these features be able to be dropped via exclude?

If there is an AnnotationList, does the first or last such entry "win"?

[azaroth42]

No reason to disallow placeholder / acccompanying containers in nested containers. bgColor is the top-most canvas/scene.