surface buffer cardinality and outputs

[Sylvain BERTRAND]

Hi,

The protocol does allow several outputs in the compositor space
but does not allow a client to render a surface based on output
properties (dpi,subpixel,frame buffer pixel format...) since
you can attach only one buffer to a surface.

If wayland wants to give a client the ability to render its
surfaces in regards of the properties of the outputs, the
protocol should be modified to take into account that a client
may have to render a surface differently for each output. It may
have a "don't care about output properties" mode which would
force the use of one buffer for all outputs.

On the other hand, if wayland does not want to let the client
render a buffer specific to the properties of each output, the
output object should not expose any of its properties to clients.
In another words, to give the subpixel format of an output to
client and not supporting rendering per output would be
inconsistent.

How does we cleanly fix this, or did I miss something?

-- 
Sylvain