Paolo Bonzini wrote:
On 12/12/2009 04:34 AM, Anthony Liguori wrote:
Firefox uses that extensively, for example to render tiled backgrounds
(though probably GTK user interface elements can do so less
successfully).
Yes, but this is just a single application. The point is that these
things are not as widely standardized on X as they are on Windows.
They are standardized (Xrender) and there are high-level de facto
standard APIs (Cairo or the Qt equivalent).
Cairo is pretty new and not widely used by applications yet. But even
Xrender is very limited compared to all of the things that GDI
supports. If it's just a matter of offloading Xrender, you could
implement compositing in VNC fairly easily.
Regarding compositing, this is done via OpenGL so even though it is
true that nothing goes through X calls, it is also true that
everything does go though a high-level API which can be sent on the
wire (cfr. AIGLX).
Right, but 3D is a different topic. Spice doesn't address this today.
Actually, compositing might really be where a protocol like SPICE
shines, since it does not generate nearly as many expose events, and
since you do not have to resend occluded contents on the wire any time
someone raises a window.
It's a trade off. If you're sending each windows contents verses
sending the visible screen, you're incurring an upfront cost assuming
interaction will be improved. This is something that I'd really like to
see perf data on because.
I have no idea how SPICE performs now, but there's definitely nothing
in a modern X Windows desktop that it cannot deal with. The only
negative point it might have compared to Windows is IMO the rendering
of text.
I think the question I was raising was not whether Spice could handle X,
but that given the things you can do with X, is all of Spice really
needed. IOW, would we get 99% of the way there with Xv accelerated
overlays and Xrender based compositing for VNC?
BTW, can someone split out these VDI patches and get them on the list?
Maybe at least an ETA of when that will happen. I think it would make
this whole discussion a lot more fruitful if we had more context..
Regards,
Anthony Liguori