I'm not sure what you mean; AFAIK X has no "standard virtual desktops". That's why every virtual wm on the planet implements them for itself. If I've missed something, please correct me.

Nice theory -- ever consider testing it?

One might start simply by looking at it while sliding; you can't implement parallax with a single pixmap, so your explanation is obviously oversimplified at the least. Could be done with two pixmaps, of course, so that doesn't prove that you're completely wrong, but I bet if we cared to we could find out for sure in less than 5 minutes.

Since one can hold the desktop "between screens" indefinitely (just drag it to one side and don't release), all you'd need is some widget that will update without user intervention. Say, the media player applet -- seek to 10 seconds before the end of a file, then get to the desktop, drag and hold it halfway. Ok, I just went and did this (which took less time than it did to write up what I was going to do), and somehow the media player applet smoothly updated to the new file's title/artist info, and even scrolled it while being floated back and forth between desktops... a nifty trick for a pixmap, eh?

Now to me, this all makes sense, given that the same level of graphics acceleration for traditionally slow (and thus often cheated) wm eye-candy is seen elsewhere (dashboard), and that the need of hardware acceleration for the core desktop was the whole reason why Fremantle couldn't run on the N8x0.