Hello dan123,
This seems it is not issued with the Widget.
You set a lot of customizations there, I would suggest you add more if states and to check the states that you set.
Another option is to use jqxListBox with and to use “indeterminateItem” method in the desired case.
Also, about your case, you could try check when all items in the ListBox are checked and the CheckBox is in ‘indeterminate’ state change its ‘jqx-checkbox-check-indeterminate’ class to ‘jqx-checkbox-check-checked’ class.
Best Regards,
Hristo Hristov
jQWidgets team
http://www.jqwidgets.com