Hi Marcel, On 2012-Feb-5, at 2:04 , Marcel Taeumel wrote:

You need to call #startStepping if you want #step to get called frequently according to #stepTime.

Actually you don't with Squeak 4.2 and Pharo 1.3 (don't know about earlier versions), because Morph>>initialize does that. But just for completeness, I did that, and it made no difference. My class is just: MorphExp>>initialize super initialize. self startStepping. self color: Color red lighter MorphExp>>step self halt MorphExp>>stepAt: t self halt and it doesn't halt if it is a subclass of SystemWindow, but does if it's any higher up the hierarchy.

Nevertheless, you may want to take a closer look at this project: https://www.hpi.uni-potsdam.de/hirschfeld/trac/SqueakCommunityProjects/wiki/...

Thanks, but I don't want the issue about unloading, and I'm not worried about it being super-smooth animation. Also thanks for the link, because it looks like interesting things are happening at HPI! ../Dave