Polygon fill algo?

[Richard Gaskin]

I was hoping to use a single polygon draw a box, using the old trick of 
making discontiguous regions by adding a blank line between lists of points.

The results draws the lines as I expected, but the fill is 
unpredictable, at least for me.  Apparently the fill rules for a polygon 
cause it to not fill some regions, even when discontiguous.

I guess I'll have to use separate objects, but I was wondering if anyone 
has a description of the polyfill rule(s), or better, a way to coerce 
discontiguous polygon regions to always be filled.

-- 
Richard Gaskin
Fourth World Systems