Subsurface support, or delegated compositing

Daniel van Vugt daniel.van.vugt at
Tue Nov 26 01:48:50 UTC 2013

If you want to generalize Scene beyond just a stack (and I think we all 
do) then even a tree is too specific. I think the complete 
generalization is simply a queryable Scene interface which then lets the 
implementation work out the real mechanics:

Surface surface_on_top_at(Point p)
Surface next_surface_below(Surface above, Point p)

Thus you're not restricted to saying there's only one surface on top. Or 
that there's only one Surface immediately below it. The answer also 
depends on the location p. There's a world of possibility that opens up 
when you throw away the notion of a linear stack.

Although subsurfaces would have a single parent, of course.

On 26/11/13 07:40, Christopher James Halse Rogers wrote:
> And this obviously only works if the model*is*  a stack, which I don't
> believe it will be in general; it'll be a tree. An obvious example is a
> browser window with two different pieces of flash embedded.

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