Rotation for basic shapes

[MrHaroldA]

I am looking into adding rotation support for basic shapes. The rotation needs to be done on the group element, as well as on the anchor group element. The rotation center point is also needed, so all shapes must register their width and height in order to support rotation.

How can I listen to changes (resize / move) for a shape so that I can update the group element? There must be something simple I'm missing right now ...

Tnx!