/// <summary> Returns the parts of a not overlapping with b. </summary>
public static Rect[] Subtract(Rect a, ref Rect b)
{
var legs = a.GetCorners().Count(b.Contains);
if (legs == 0)
{
return a.Substract0Legged(ref b);
}
else if (legs == 1)
{
return a.Substract1Legged(b);
}
else if (legs == 2)
{
return a.Substract2Legged(b);
}
else
{
Contract.Assert(legs == 4);
return EmptyCollection<Rect>.Array; //rect is already contained in r
}
}