From Bugzilla Helper: User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.1a+) Gecko/20020630 BuildID: 20020630 Lately the DHTML example # 13 (resource:///res/samples/test13.html) is totally messed up. Sometimes this page works perfectly and the DHTML is very fast, but sometimes, running mozilla again the speed is horrbile and the animation is not smooth at all. The different words jump form one location to another making it look completly messed up. This didnt happend before, noticed this the last weeks. Reproducible: Sometimes Steps to Reproduce: 1. Go to DHTML Viewer Demo #13 2. if it runs smooth, surf around a bit and go there again

This is very easy to reproduce on Windows XP, on Windows 2000 and Mac OS 9 I have not succeded in reproducing. When the DHTML gets messed up in XP, it does not even help to restart the browser. This behavior is extremly weird.

There are some regressions around that could have caused this - let's investigate.

The easiest way to reproduce this on XP is to to Viewer Demo #13, do not have the browser maximized so you can see your desktop. Now rightclick on your desktop and select Properties. Doing this messes up the example completely. Maybe its cause I only have a Pentium II, 400 Mhz with 256 RAM?

Using trunk build 2002071108 on win-xp,1.1ghz,512ram and a GeForce2 Go video card there is no difference when viewing the "properties" of the desktop.

What happends is not the animation goes slower, it just gets messed up, reminds me of bug 129953. Closing down the Desktop Properties fixes this.

At home I have a Athlon 1900+, 256 MB, Win XP and noticed the following: Running a program that needs a lot of cpu at the same time, for example Windows Media Player reproduces this. IE animations does not slow down if you are running WMP at the same time.

Nominating for nsbeta1 as this a regression of DHTML performnace.

Now I am testing this on Windows 98 (Pentium III, 512 MB) and I easily see this. Believe more and more that this is a dupe of the new frame-drops bug that Markus reported. Cannot remember the bug number though. :-(

Ya - sounds so. It's bug 157401.

WFM, build 20020730! After the fix in bug 153083, I do not see any frame drops.