Create a Region and add two other Regions to it. Style both Regions with CSS by using -fx-shape and L-shaped concave polygons like on the attached image (https://dl.dropboxusercontent.com/u/84552/issues/rt-31902.png). Now set on both L-shaped Regions setPickOnBounds(false) so that it will take the real shape for picking. You will figure out that it won't work like expected. means there are areas in the shapes that do not react on MouseClicks/hovers. It seems to be related to the shape calculation. I've tried hover in CSS which has the same problem as using setOnMousePressed() on the Regions.

Example code: https://dl.dropboxusercontent.com/u/84552/issues/rt-31902.zip