callback. and callback that can be overridden by clients to do some actions. The
duringmethod is called each time the mouse moves from its current cursor position after a mouse button has been pressed on the drag switch. The
callbackmethod is called when the mouse is released.
The program Drag.m3 uses a drag switch. The text field is used to display the current position of the cursor while a button is held down and the cursor is being dragged. When the mouse button is released the callback is invoked. Four steps during the execution of the application are shown in the following images. (The cursor is not shown.)