I was trying to play little pixel animations on a xhtml page by switching 52 KByte gifs in a matrix "on and off" by swapping the image with javascript at 25 frames per second. All the browsers out there perform very poor and producing lots of CPU load. The javascript doesn't seem to be the problem - in spidermonkey the whole script runs very very fast. The gifs are in the cache after the initial page load - so it must be the rendering I assume. I've put the (my) testcase on http://smyck.de/screentest/. The latest webkit comes very close to desired frame rate on my macbook pro but on older machines its slow and burns the cpu. In case you wonder what it is for, check out http://blinkenlights.de/ We wanted to make a web app to let the users create movies for the next installation and play their movies on the web without flash etc.
The issue is visible on all tested by me browsers: Opera, Minefield and Webkit. I opt for WONTFIX for this bug but the final decision is up to Webkit Team.
Nothing to do here