Some considerations

[Keith Whitwell]

Martijn Sipkema wrote:
> [...]
> 
>>I don't really see the problem.  In the current case there is an
> 
> application
> 
>>rendering to an offscreen buffer (its backbuffer) and there is some sort
> 
> of
> 
>>swapbuffers operation - either a copy or a pageflip.  I don't see what
> 
> would
> 
>>be different in a compositing situation.
> 
> 
> It would no longer be possible to take advantage of per window framebuffer
> configurations and zero-copy swaps as e.g. SGI hardware provides.

This is what I mean by 'pageflip', and I don't see why it wouldn't be possible 
if it was provable that the compositing operation was identical to a copy.  It 
might not be possible with drivers as they stand, but that doesn't mean that 
the architecture prevents it.  There will eventually be changes flowing down 
to the drivers as a result of this work.

Of course if you choose to make your fullscreen app non-opaque, of course the 
driver can't pageflip.  That's not the driver's fault though, nor OpenGL's.

Keith