Volume 6A: Motif Programming Manual

A drag and drop help dialog

The new HandleDropLabel() routine handles the case when the dropAction field is set to XmDROP_HELP. In

this case, the routine creates an InformationDialog if it has not already been created. The HandleDropOK() and

HandleDropCancel() routines are registered for the OK and Cancel buttons in the dialog. If the dialog already

exists, the necessary fields in the client structure are specified so that the callback structure information is passed

to the callback routines as client data. If the user has performed a normal drop operation, the drop proceeds just as it

did in editor_dnd.c.

The HandleDropOK() routine is invoked when the user presses the OK button in the help dialog. This routine

proceeds with the drop by calling XmDropTransferStart(). The status of the transfer is based on whether the

drop performs a copy operation or not. HandleDropCancel() cancels the drop when the user presses the Cancel

button by -calling XmDropTransferStart() with XmN-transferStatus set to XmTRANS-FER_FAILURE.

One thing to note about both of these procedures is that they get the XmDropProcCallbackStruct from the

client_data parameter, since the call_data parameter is the callback structure for the dialog.

19.5.5 Providing Custom Drag−under Visuals

Under the preregister protocol, the drop site does not participate during the drag. The initiating application handles the

drag−under visual effects ...