Callback whenKillFocus;
Callback whenSetFocus;
etc.
in Ctrl
that would make writing complicated forms a lot easier.
I understand the sentiment, but 'etc.' can mean a lot... In any case, each such thing means 8 bytes more in sizeof(Ctrl), which is not very good for filling e.g. ArrayCtrl with widgets.
Generally, for focus games, ChildGotFocus and ChildLostFocus virtual methods in parent often even better than those individual callbacks.