Full screen GtkDrawingArea performance sucking - help me!

[Alex Jones <alex weej com>]

Hi list

In my quest to write an awesome backdrop rendering app, I have this test
program that draws random colours to a GtkDrawingArea. For me, any size
over about 300x300 at 60fps just causes insane lag in Xorg -- the
renderings seem to queue up. If I run cairo clock maximised full screen,
it literally LAGS by about 5 seconds. Telling it to close takes ages, as
if the X connection is completely saturated. My own cairo clock which
draws the second hand smoothly between intervals shows that it seems to
run at less-than-real-time, but still smoothly. Eventually, the clock
skips ahead by 10 seconds or so.

I have a 2.8 GHz Pentium 4 with 1 GB of RAM, nothing using my CPU and a
Radeon 9800 Pro with the r200 drivers. What's going on? This is a total
spanner-in-the-works for me.

Cheers