After an update to the newest X with mesa drivers (radeon), simdock started to flicker. Turns out this was caused by changing icons y-variable always by zoomChange, even when reducing the change for width and height in the last steps to not step over, thus replacing the icon a bit (stepping over the paintarea?). It's unclear to me why this lead to flicker now.
Instead of using the mouse events for the zoom animation, start a timer and control the animation in there. Makes the animation much nicer, but costs more cpu. TODO1: Remove old settings (distance) or restore old animation method as an option TODO2: Add settings to control animation smoothness