Nathanael wrote:
> 
> I was aware of the fact that the old recognizer is using the pen trail, but
> when I implemented Genie I thought it would be cool if the Genie trail would
> be a real Morph and we could even use it properly on a BouncingAtomsMorph or
> anything else that is moving around. However, since trails are anyway only
> visible for a short time, performance is much more important than fancy
> features like correct updating on top of a BouncingAtomsMorph. If we can
> make it faster using a single Stroke Morph instead of multiple LineMorphs
> that would be cool! Otherwise, I'll probably just switch to using the trail
> pane (as turtles and the old recognizer do it).

It might be possible to use a Morph *and* a pen trail.  If you can
trick the StrokeMorph into not invalidating its bounding rect, the pen
trail can take care of fast drawing over static Morphs (no slowdown
for expensive Morphic redraws).  On the other hand, when drawing over
dynamic content like a BouncingAtomsMorph, the changing background
would invalidate the region, and the StrokeMorph on top would take
care of re-drawing the stroke.  It's more complicated, but I think it
could get you both great speed in the normal case, and the cool
display property you would like on top of dynamic content.

-Jesse