A standard way to do that is the following: If the polygon external ring is composed of **n** points **(P1,P2,...,Pn,P1)** and a hole internal ring of **m** points **(H1,H2,...,Hm,H1)**, try to draw the polygon composed of the single following external ring: **(P1,P2,...,Pn,P1,H1,H2,...,Hm,H1,P1)**. This is equivalent of drawing a fictive imperceptible corridor between the external and internal ring like there:

![enter image description here][1]

It can be generalised in case of several holes: **(P1,P2,...,Pn,P1, H11,H12,...,H1m1,H21,H11, H21,H22,...,H2m2,H21, ... , P1)**


  [1]: https://i.sstatic.net/bFIvv.png