This property can be used to allow the user to make multiple selections on the tree. Three built-in icons are used to show the ‘selected’ ‘deselected’ and ‘ambiguous’ states. If ‘propagate’ is true, a leaf node is always in state 1 or 0 – nodes higher up the tree will reflect the logical sum of the states of all their children (1 if all 1s, 0 if all 0s, otherwise ¯1). Changing the state of a higher-level node automatically switches all the descendants into the same state.