void AddRectangle(long x,long y,long w,long h)
Construct and add a rectangle of the given lower left position
x,y and size w,h.
void DeleteRectangles(void)
Remove and delete all rectangles on the list.
void Prune(void)
Remove and delete all rectangles on the list whose width or height
is less than 1.
long Intersect(EW_Rectangle *other,EW_RectangleList *intersection)
Compute the intersection of this list and the given other
rectangle and put the pruned result into intersection.
The pointer intersection can be NULL,
in which case the result is discarded.
Intersect returns TRUE if there was some intersecting area
(the other rectangle overlapped some area of the listed rectangles).