Implementing a Generalized Drag-and-Drop in X

Drag-and-drop operation is a well-recognized and widely applied mechanism in the development of graphical user interfaces (GUIs). Most of current approaches in design and implementation of such a operation are limited to some specific objects (such as icons or drag-and-drop widgets), and are usually complex, system-dependent, and time-consuming. This paper proposes a generalized semantic and protocol for drag-and-drop that makes the draggable and droppable as intrinsic properties of any GUI objects (just like the colors and other appearance of an object) and allows each object to customize its own semantic of drag- and-drop. Therefore, the drag-and-drop feature is integrated as an inherent part of a GUI window system and all details and complexities of its implementation can be hidden from end users. The framework of generalized drag-and-drop could be applied to any GUI system. A prototype implementation in the Xt Athena widget set of X11R5 on a Unix system is reported in the paper.