surface buffer cardinality and outputs

[Sylvain BERTRAND]

Hi again,

I put some more thoughts in those issues.

A client knows on which outputs its surfaces span over. Then the
client is in charge of configuring its rendering to find the best
trade off, but with one buffer. If the surface was entered on 2
outputs with really different DPIs... well it should configure
its rendering based on the average of output DPIs? The user would
move/resize the surface on one output if he wants to get a GUI
rendered properly again.

For the double buffered flow and very long page flips that could
be induced for a surface spanning over several outputs... well
too bad for the surface and the client.

Regarding a discret vs continuous compositor space. If we accept
the previous tradeoffs, a dynamic continuous compositor space is
fine.

But I'm still kind of uncomfortable to hand over to the
compositor scaling in the case of fullscreen and buffer transform
in the case of output tilting (renaming transform to tilting
would not be a bad idea).

Another though which targets sub-surface interfaces: are the
hardware overlays for YUV buffers that more energy efficient than
GPU scaling/color space conversion since most the energy would be
burned into the video decoding anyway?

thanks.

-- 
Sylvain