Re: [Qemu-devel] Spice project is now open

[Anthony Liguori]

Izik Eidus wrote:
> > > > By the time we get to video memory, the display server has already 
> > > > straightened out what portions of the screen are visible and what 
> > > > aren't.  It will not render a hidden window and then render
> > > > another window on top of it.
> > > >     
> > > >         
> > > I dont understand, if you have applciation that draw Rectangle, and
> > > just another Rectanlge on top of it, wont it hide it?, doesnt we
> > > want just to send the newest Rectangle?
> > >   
> > >       
> > If you're using something like gdk, the toolkit double buffers
> > windows by default and does a single flip on expose.  So this sort of
> > thing never makes it way to the X server.  But the other point is, if
> > you draw a rectangle with gdk, all the X server ever sees is the
> > drawing of an image.
> >     
>
> Spice work on the driver primitives it doesnt know what is GDK, if the
> X driver will draw rectangle and then another rectangle, VNC will have
> to draw it twice, spice not.
>   

The point is, there isn't a "draw a rectangle" primitive in X.  There 
also isn't a "draw some text using this font" in X.[1]

These things exist at higher levels (like GTK and QT).

[1] there actually are but modern applications don't use them.

> Ohh, The performence is much better user interactive and higher density
> the user interactive come from the paravirtual device and the fact that
> we dont send commands that were "hide" into the client.
>
> The higher density come from the fact that the server that run the VM
> (qemu) almost never have to render the stuff....
>   

With the Linux guest driver?  If you can quantify that, it would be very 
useful.

> > Are there plans to integrate Spice support in gdk (or cairo)?  I
> > think that would be required to get performance parity with Windows.
> >     
>
> Can you expline more what you mean?
> Spice work on the driver primitives, so I am not sure I understand here
> what you suggest...
>   

I think the point I'm trying to get across, is that Windows has a 
centralized architecture of drawing primitives and interfaces that is 
relatively easy for drivers to hook into.

Linux doesn't have this.  Different things are handled in different 
places and some layers (like GDK) aren't really made for hooking into.

What I'm trying to understand is whether it will be possible to 
implement a lot of the Spice accelerations for Linux guests.

Regards,

Anthony Liguori