Comment 2 for bug 769605

Here is a video demonstrating the problem: http://www.youtube.com/watch?v=NOpwdUwyNys

I recorded this video on my mobile phone so the quality is a bit low, sorry about that. But I wanted to faithfully capture the speed and I figured a desktop recorder might prevent me from doing that.

So, first I switch between two windows while using Ambiance. Notice that the gears stop moving for about a second while I do this. In fact, the whole display of the computer freezes up during this time.

Next, I minimize/restore a window. Notice that the animation barely even shows because it is so laggy, and again the whole display freezes up.

Next I switch to clearlooks theme and repeat the tests, and no noticable delay is observed.

Also note that glxgears is running in a frankly tiny window and is locked to vsync so it only renders 60 frames per second. This should use a minimal amount of resources. It certainly shouldn't cause this much lag. If vsync is disabled glxgears hits 6000 fps. Also note that the lag increases when more graphically intensive software is running, but is always significantly worse with light-themes than with any other theme.

I suspected that the issue was caused by the huge drop shadows of light-themes so I attempted to disable them by editing the theme XML file setting the radius to 0 as follows:

<shadow radius="0" opacity="0.75" color="#abde4f" x_offset="1" y_offset="4"/>

However this did not make any difference to the speed.