Enhancements for Render composite request

[Jim Gettys]

Keith Packard wrote:
> The render composite request has a couple of glaring failures:
>
> 
> It seems like operation 2) should be an option on the picture object;
> set a sync mode on the picture and all operations would be covered by
> that mode. It would be 'best effort', so that drivers not supporting the
> sync mode would simply skip it. The question is how fancy this option
> should be; in the simple case, we'd make it just avoid tearing, more
> complex cases could involve having sequential operations to the same
> picture wait for a specific frame number. I'd love to have comments on
> precisely which 'swap modes' would be useful here.
> 
> 
>
This was exactly planned for in the XSync extension: all that awaits 
doing is to hook up vertical retrace to a an XSync counter, and away you go.

We even tested it all. (a long time ago, in a galaxy, far, far away).

It's just been awaiting having a device driver to implement it.
				- Jim