I'm sure it's occurred to people before, and perhaps there's a good reason
why it is not currently (1.2.1 for me) implemented. But I would really like
to be able to see the shape of the brush I am using to paint with as an
outline, I assume this would be a mouse pointer.

In the event that this is not achievable X or GTK to control the pointer,
what alternatives exist? Is it possible to carry some kind of
semi-transparent shape (or as in photoshop an outline in the shape of the
brush) around while the pointer is over the image and the tool is a
painting tool?

I searched for bugs like this but was not able to find any in the
too-hard-basket. If I have failed to spot the obvious, some clue would be
appreciated. 

Thanks for a great tool.