void EZ_GetFancyListBoxSelectionIdx(EZ_Widget *flistbox,
int *row_ret, int *col_ret)
EZ_GetFancyListBoxSelectionIdx returns the array indices
of the selected item(s) in a fancy listbox widget.
If no selection has been made, it returns -1 to row_ret.
There are two selection mode in a fancy listbox. In row mode, a row
is selected at a time. A row usually consists of several items. In
this case, EZ_GetFancyListBoxSelectionIdx returns 0 to