Don't forget that SFGUI not only serves as a widget toolkit, but in general as a framework for designing your own widgets should the need arise. SFGUI gives you access to it's numerous interfaces for handling almost all kinds of events and drawing at a very low level (basic primitives, lines, text etc.) as well as interaction with other widgets. If you have a vision of a widget that you might want, it is highly probable that you will be able to implement it with SFGUI.
SFGUI is still a work in progress, but progress is being made, sometimes slower than usual
. At some point we plan on adding tooltip support, modal window support, keyboard-only control e.g. tabbing through widgets, and most importantly a bitmap rendering engine. We did have one in development named Bob but I have no idea where he wandered of too
. I might probably end up writing one myself if I feel like it needs to be done at some point.
The main problem right now, is that creation of custom widgets is not documented at all. It is possible, however to do anything meaningful you really would need to take a look at how existing widgets are implemented and figure things out on your own. This should change sometime in the future however, since we don't plan on releasing something without adequate documentation
.