Kid 0 - XuiRadioBox
"Selection" callback on Enter KeyDown
"Selection" callback on MouseDown
v0 : $$FALSE = not selected
$$TRUE = selected
XuiRadioButton grids display a text string and is show as not selected or selected depending upon whether its border is raised or lowered.
Selecting a XuiRadioButton grid first deselects all other XuiRadioButton grids in the same window and group, then selects itself. Thus no more than one XuiRadioButton grid in a group is ever selected.
XuiRadioButton grids generate a Selection callback message with v0=$$FALSE when deselected and v0=$$TRUE when selected.
A window with a single XuiRadioButton is not particularly useful, since once selected, the only ay the user can deselect it is by selecting another XuiRadioButton grid in the window, none of which exist.
