Registers a callback that's fired when a shape is drawn.
Returns an ID which can be passed to unlisten() to unregister the callback.
| Usage | Returns | DrawingTools.onDraw(callback) | String |
| Argument | Type | Details | this: ui.map.drawingtools | ui.Map.DrawingTools | The ui.Map.DrawingTools instance. |
callback | Function | The callback to fire when a shape is drawn. The callback is passed three parameters: the added ee.Geometry, the GeometryLayer to which the geometry was added, and the ui.Map.DrawingTools widget that the event listener is bound to. |