Re: A possible problem with an external compositing manager

Keith Packard <[email protected]> writes:

> Not true; the XSync will wait only until the X server has queued the 
> rendering operations to the video card.  Then there is the delay between 
> when the frame is drawn to video memory and when it is actually visible on 
> the screen.  The GetImage trick reduces arbitrary graphics card latency to 
> bounded retrace lacency.

Ah, thanks for explaining. I didn't realize that difference between
GetImage and XSync(). Does hardware have facilities to report when
they have executed a given command?

> Assuming our compositing manager can do screen updates within some 
> reasonable time bound, the GetImage trick will do the same here, with 
> perhaps a longer lag.

Only if GetImage actually is actually guaranteed to return the
contents of the root window, right?


Søren