Initiating a Drag

Common Desktop Environment 1.0 applications start a drag by calling DtDndDragStart(). This function performs some desktop-specific setup and calls XmDragStart() to initiate a drag. The DtDndDragStart() function synopsis and parameter usage are described as follows:

Widget DtDndDragStart(
 	Widget				dragSource,
 	XEvent 				*event,
  	DtDndProtocol				protocol,
 	Cardinal				numItems,
 	unsigned char				operations,
 	XtCallbackList 	convertCallback,
 	XtCallbackList dragFinishCallback 	ArgList				argList,
		Cardinal				argCount)

Widget dragSource

The widget that received the event that triggered the drag.

XEvent *event

The button press or button motion event that triggered the drag.

DtDndProtocol protocol

The protocol used for the data transfer. The protocol may be one of the following:

DtDND_TEXT_TRANSFER

DtDND_FILENAME_TRANSFER

DtDND_BUFFER_TRANSFER

Cardinal numItems

Specifies the number of items being dragged.

unsigned char operations

Specifies options supported by dragSource. The options are XmDROP_MOVE, XmDROP_COPY, and XmDROP_LINK. A drag source may support any combination of these operations. You specify a combination of operations by using or. For example, to support the move and copy operations, specify XmDROP_MOVE | XmDROP_COPY.

XtCallbackList convertCallback

This callback is invoked when a drop has started and the drop zone has requested data from the drag source. The convertCallback is explained in more detail in the next section.

XtCallbackList dragFinishCallback

This callback is invoked when the drag-and-drop transaction is complete. The dragFinishCallback should reset the dragMotionHandler() and free any memory allocated by the drag source during the drag-and-drop transaction.