[Etoys] setVertexCount (Star and now Polygon morph)

Jerome Peace peace_the_dreamer at yahoo.com
Mon Mar 2 21:01:54 EST 2009

Hi Yoshiki and crew.

I am in the middle of looking into Hayashi-san's fixes.

Adding setVertexCount: to polygon has some nice features.
It actually does solve the problem of adding to one vertex.
Also I haven't yet seen the problems crop up with one vertex morphs
raising debug problems.

On the other hand since I was looking at it I put on my Fearless-Bug Tracker hat. And called on my imaginative* trouble making assistant Puck.

We observed the following. Currently (before patching) say you set the number of star vertices to something odd like 9 . What happens the second time you execute the assignment.

Also when I repaired stars I chose to make sure there were a minimum of 
two points (4 vertices). Currently using the assignment you can set star to have 2 vertices. This was interesting in a Papert sort of way**.

So I let Puck take over.  He tried setting the star to -6 vertices.
And smiled ear to ear as we got a wonderful crash. 
Debug boxes, an emergency evaluator and of course the star was invalidated.

I haven't tried yet but I suspect that similar things can happen to polygons that way.

I don't think this invalidates Hayashi-san's fixes. It does point to some tightening up being required in what gets passed along from the tile scripts.

I also think it would be cool to have a triangle handle appear when you are down to one vertex. So I still recommend combining the two repairs with some extra-bulletproofing thrown in to prevent puckish mischief.

Yours in curiosity and service, --Jerome Peace

*(Puck insists I NOT call him my imaginary assistant)

**(There are no wrong results only interesting outcomes -- Seymour Papert somewhat paraphrased and folk processed)

Cheers -Jer


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