@Abhishek: I'd rather not require extensions to have a new method for resetting font sizes. Instead, a virtual event can be bound to a callback by the extension if it needs to know about a font change.

@Alejandro: It looks like there's a bug in ZoomFont.py where the cursor can go off screen which has propagated into these patches. That's my fault.

I'll take a look at these points later this week.