Volume 6A: Motif Programming Manual

The only reason that you should specify the XmN-dragInitiatorProtocolStyle and

XmN-dragReceiverProtocolStyle resources in application code is if your application is going to

support only one of the drag protocols. In this case, you should set the resources to force the application to use

the supported protocol. You can retrieve the Display object for the application using XmGetXmDisplay()

and then use XtVaSetValues() to specify the resources. You can also use XtVaGetValues() to check

the values of the protocol resources.

If your application supports both drag protocols, you can specify the protocol resources in an app−defaults file

to indicate the application's preferred protocol. By default, an application uses the preregister protocol because

XmN-dragInitiatorProtocolStyle is set to XmDRAG_PREFER_RECEIVER and

XmN-dragReceiverProtocolStyle is set to XmDRAG_PREFER_PREREGISTER. If you have

implemented custom drag−under visuals with an XmN-dragProc, you should set the protocol resources to

XmDRAG_PREFER_DYNAMIC so that the dynamic protocol is used whenever possible. You can set these

resources in an app−defaults file as follows:

*DragInitiatorProtocolStyle: DRAG_PREFER_DYNAMIC

*DragReceiverProtocolStyle: DRAG_PREFER_DYNAMIC

If you set the protocol resources in an app−defaults file, users can specify their own values in a resource file. Users

that want to ensure good performance should specify a preference for the preregister protocol, while users that want

sophisticated drag−under effects should ...