Code review comment for lp:~robertcarr/mir/alpha-for-nested-servers

I can imagine that we might sometimes want alpha on a nested "FB", but always seems wrong.

Can I paraphrase what I think is being said:

The host will have surfaces for nested sessions for example unity8 and greeter.

There's no value (and cost) to alpha for the unity8 surface.

The idea is that the greeter surface can overlay the unity8 surface using transparency. Is this alpha varied across the surface? (For shapes? Or gradations?)

If we need variable opacity across the surface then the greeter needs to be able to request a surface with alpha. If not, then perhaps there are alternative options.