This header provides a way to handle drags using the Event sublibrary.
This function must be called to initialise the drag system for use with the Event sublibrary before you use other Drag functions.
attachNULLhandler should be TRUE if you want to use an update handler to do things on Null events. You usually only need this if you are dragging user-redrawn objects, or are using the drag-and-drop protocol between applications.
This sets the functions which will be called during the drag (uproc) and after when the drag finishes (cproc). Either of these may be NULL in which case it will not be used. In any case, uproc will only be called if you told Drag_Initialise that you wanted to claim Null events.
userdata is a pointer that is passed to your handlers for your own use.
Note that this only sets the handlers, it doesn't actually start the drag - you need to call Wimp_DragBox or an equivalent to start the drag.
This type is used to define functions called by the Drag library during and at the end of a drag. The userdata is passed to these functions to indicate what drag is being updated or finished.
This is used to keep track of which function to call during the current drag.
This is used to keep track of which function to call when the current drag ends (when the mouse button is released).
This contains the user data pointer for the current drag.