* Documentation for indeterminate checkboxes
* Unit tests for indeterminate checkboxes
* Implement indeterminate checkboxes
* Simplify indeterminate checkbox example
* Slightly simplify refresh logic for indeterminate
That five-line if statement can be turned into a simple assignment.
* Use "yes" and "no" for checkbox indeterminate attr
This makes the "indeterminate" attribute of the checkbox widget work the
same way as other boolean attributes of other widgets.
* Fix bug with invertTag attribute
One place in the checkbox widget code was checking invertTag for
Javascript truthiness rather than the value "yes", which could have
produced incorrect results if anyone wrote invertTag="no". Fixed.
8dec674121