surface buffer cardinality and outputs

[Bill Spitzak]

Jerome Glisse wrote:

> Yes this is the idea i had, the client render in screen space and send
> to the server a possible bigger buffer than what its window need.
> Client send the screen space buffer size (wdith & height) but also the
> untransformed size (width and height) and the transformation matrix
> that was use. You also need a rounding convention which in this case
> should be ceil

I don't think you need any rounding convention. The transformation 
matrix says includes translation and says how the client mapped the 
untransformed size to the buffer. If it clipped off some corner pixels, 
or it padded it with some blank area, the compositor will be able to 
figure this out from the matrix and the size of the buffer.

> All other information such as opaque region will be given untransformed.

I agree with this. Also the positions of popup windows and subsurfaces 
are untransformed, and any other communication about positions inside a 
surface from the client to the compositor. The only thing that is 
transformed is the image in the buffer.