I really don't understand why, given that you have a scene graph objectand a place for the scene graph to be rendered to, you feel it's important
to have a middle-man object.
I understand that there is a concern that authors will accidentally change
the settings and that changing the settings used in a particular context/
canvas pair is expensive. But I don't see how a middleman object would
help. If an author could accidentally use different settings when binding
a context to a canvas, why couldn't an author accidentally use a different
middle man object?