3-state checkbox

[andrewc]

Dear all,

I would like to create a 3-state checkbox widget in CEGUI, i.e. one which is checked, unchecked, or indeterminate to indicate use of a default defined elsewhere. The indeterminate state would probably look like the filled square in a 3-way checkbox in Windows.

I've searched through all the documentation I could find on creating custom widgets, but it's all pretty brief and I still have no real idea where to start. Can anybody please give me a quick run down of what I would need to do to achieve a working solution?

By the way, I need a lot of these on the screen in a limited space, so using labelled radio boxes is not a good alternative.

Many thanks,
Andrew