Composite and Shared Memory?

[Amir Bukhari]

> -----Original Message-----
> From: xorg-bounces at freedesktop.org [mailto:xorg-bounces at freedesktop.org]
> On Behalf Of Keith Packard
> Sent: Monday, November 15, 2004 6:26 PM
> To: Discuss issues related to the xorg tree
> Subject: Re: Composite and Shared Memory?
> 
> 
> Around 11 o'clock on Nov 14, Amir Bukhari wrote:
> 
> > this give us the ability to use Shared Memory Pixmap as off-screen, so
> we
> > didn't need to copy the redirected window pixmap to our shared memory
> > pixmap each time Damage occure.
> 
> That's a neat idea; I'm not sure how we could make it work though.
> Composite needs to create new pixmaps whenever the window size changes,
> and it can't be asynchronous (or we lose a bunch of X semantics).  So,
> somehow you'd have to have shared memory space sufficient to hold the new
> window contents.
> 
> Alternatively, we could create a request to *replace* the current pixmap
> with another which could be in shared memory.  That would have to be the
> 'right' size (or Match error).
That what I have meant, adding a new request to replace the current pixmap
will be the right way and let application choose it way to track if size of
window change, then it know that the shared pixmap no more point to window
pixmap.
Composite should change the pixmap as usual when window size is change!

But what about performance, when using shared memory pixmap with
Composite/RENDER, is that get to performance killing?

-Amir