Feature request: Tri-state checkboxes and multiple selection button groups

[williamclocksin]

I am converting a large project from NeXTStep to JavaFX. NeXTStep API for UI controls had two great features I can't find in JavaFX or in ControlsFX, and I can't see how to easily implement it myself in JavaFX.

1. Check boxes could be tri-state, showing a line instead of a tick for the third state.
2. Multiple selection in button groups. Like a toggle group, but 1 or more buttons could be selected.
   Both features are useful for showing the status of a group of items that have been selected but have different values, for example.
   Interested?

[williamclocksin]

Correction: I can see how to use the indeterminate state for buttons but don't want the user to cycle through them.