Demonstrates a way to do Yosemite-style animated controls.
I don't claim this is the only, or even the best, way to do this. But it is relatively simple, and aside from the drawing code, it is resuable.
In fact, left as an exercise to the reader would be to implement this so it could be subclassed to do the actual drawing, or so it could be intialized or configured wiht a drawing proc.
This code is placed in the pubic domain - no rights reserved. Do with it what you like.
If you use it, I'd be happy to hear about it, and if you really like it, feel free to purchase a license for Keyboard Maestro to say thank you.