This section describes how to implement objects that can be dragged around and dropped onto other objects.
Many user interfaces allow one to drag particular objects around with-in the interface.
For example, dragging files to other directories, or an icon to another window to open the document it refers to. Mozilla and XUL provide a number of events that can handle when the user attempts to drag objects around. A user can start dragging by holding down the mouse button and moving the mouse. The drag stops when the user releases the mouse. Event handlers are called when the user starts and ends dragging, and at various points in-between.