Has anyone performed any usability testing with tri-state checkboxes? For clarity, by "tri-state", I mean the variety in which a single checkbox represents (a) everything (such as sub-checkboxes) selected (displayed as a checkmark inside a box), (b) partial selection (filled square or minus inside box), and (c) nothing selected (nothing in box).
I've attached an example from jsTree (thanks, Matt).
My gut tells me that this widget is confusing, because:
- Especially in a Web application context, this is not a standard widget. (However, that is not necessarily a reason not to use a widget, especially if that's the only reason.)
- The user can only select two of the states (a and c above). The partial selection state is a result of other selections. Thus, it seems that this widget is overloaded, being both a display "widget" and a selection control, but the selection and display is not one-to-one.