Magnifies the items under the mouse while the button is pressed down.
Do not associate any action with the button.
Pans the view if the mouse is dragged while the button is pressed down.
Starts a multiple selection operation.
Draw a zoom-lasso if the mouse is dragged with specified button pressed down.
The Cancel value can be combined with Pan or Select. Thus if a user presses the mouse button while drawing an item, the operation will be cancelled; otherwise dragging with the specified button will start panning or drawing a selection rectangle.