ok.
I already have the TristateCheckbox class (subclass of Button) which is working fine and very simple to call
  - automatically checkbox
  - automatically cycling through 3 states
  - can set the order of the states (first false or true after undef) - just in case
  - so you can simply call TristateCheckbox tscb = new TristateCheckbox(parent, SWT.NONE);
  - enums are TristateValue.TRUE/FALSE/UNDEF -> but I would place the enum into PersistentObject for free access
  - I'd place it in ch.elexis.core.ui.util - is that ok?


If we just support ONE / ZERO / Remainder undef makes me happy! With int you could still have null in the db as undefined.
This way we define it crystal clear - no "true"/"false", "oui"/"non", "si/no" and so on...

PersistentObject is perfect. I'll define there
  - PersistentObject.getTriStateBoolean() which returns enum TristateValue
  - PersistentObject.setTriStateBoolean(TristateValue newVal)
  - the tristate enum TristateValue.TRUE/FALSE/UNDEF 

coming quite soon as new commits to this branch

Gruss, Harry