Registers a callback that's fired when a shape is selected.
Returns an ID which can be passed to unlisten() to unregister the callback.
|ui.Map.DrawingTools||The ui.Map.DrawingTools instance.|
|Function||The callback to fire when a shape is selected. The callback is passed three parameters: the selected ee.Geometry, the GeometryLayer to which the selected geometry belongs, and the ui.Map.DrawingTools widget that the event listener is bound to.|