onMouseDownevent handler. The Mouse sensor is initialized if the mouse down event was triggered by the left mouse button.
distanceproperty represents the distance, in pixels, by which the mouse needs to be moved before a drag start event is emitted.
delayproperty represents the duration, in milliseconds, that a draggable item needs to be held by the mouse for before a drag start event is emitted.
toleranceproperty represents the distance, in pixels, of motion that is tolerated before the drag operation is aborted. If the mouse is moved during the delay duration and the tolerance is set to zero, the drag operation will be immediately aborted. If a higher tolerance is set, for example, a tolerance of
5pixels, the operation will only be aborted if the mouse is moved by more than 5 pixels during the delay.