XmDropTransfer man page

XmDropTransfer — The DropTransfer widget class


#include <Xm/DragDrop.h>


DropTransfer provides a set of resources that identifies the procedures and associated information required by the toolkit in order to process and complete a drop transaction. Clients should not explicitly create a DropTransfer widget. Instead, a client initiates a transfer by calling XmDropTransferStart, which initializes and returns a DropTransfer widget. If this function is called within an XmNdropProc callback, the actual transfers are initiated after the callback returns. Even if no data needs to be transferred, XmDropTransferStart needs to be called (typically with no arguments, or just setting XmNtransferStatus) to finish the drag and drop transaction.

The XmNdropTransfers resource specifies a transfer list that describes the requested target types for the source data. A transfer list is an array of XmDropTransferEntryRec structures, each of which identifies a target type. The transfer list is analogous to the MULTIPLE selections capability defined in the Inter-Client Communication Conventions Manual (ICCCM).

The DropTransfer resource, XmNtransferProc, specifies a transfer procedure of type XtSelectionCallbackProc that delivers the requested selection data. This procedure operates in conjunction with the underlying Xt selection capabilities and is called for each target in the transfer list. Additional target types can be requested after a transfer is initiated by calling the XmDropTransferAdd function.


An XmDropTransferEntry is a pointer to the following structure of type XmDropTransferEntryRec, which identifies a selection target associated with a given drop transaction:

typedef struct
        XtPointer       client_data;
        Atom target;
} XmDropTransferEntryRec, *XmDropTransferEntry;

Specifies any additional information required by this selection target


Specifies a selection target associated with the drop operation


DropTransfer inherits behavior and a resource from Object.

The class pointer is xmDropTransferObjectClass.

The class name is XmDropTransfer.

New Resources

The following table defines a set of widget resources used by the programmer to specify data. The programmer can also set the resource values for the inherited classes to set attributes for this widget. To reference a resource by name or by class in a .Xdefaults file, remove the XmN or XmC prefix and use the remaining letters. To specify one of the defined values for a resource in a .Xdefaults file, remove the Xm prefix and use the remaining letters (in either lowercase or uppercase, but include any underscores between words). The codes in the access column indicate if the given resource can be set at creation time (C), set by using XtSetValues (S), retrieved by using XtGetValues (G), or is not applicable (N/A).

XmDropTransfer Resource Set
Name Class Type Default Access

XmNdropTransfers XmCDropTransfers XmDropTransferEntryRec * NULL CG

XmNincremental XmCIncremental Boolean False CSG

XmNnumDropTransfers XmCNumDropTransfers Cardinal 0 CSG

XmNtransferProc XmCTransferProc XtSelectionCallbackProc NULL CSG

XmNtransferStatus XmCTransferStatus unsigned char XmTRANSFER_SUCCESS CSG


Specifies the address of an array of drop transfer entry records. The drop transfer is complete when all the entries in the list have been processed.


Specifies a Boolean value that indicates whether the transfer on the receiver side uses the Xt incremental selection transfer mechanism described in X Toolkit Intrinsics—C Language Interface. If the value is True, the receiver uses incremental transfer; if the value is False, the receiver uses atomic transfer.


Specifies the number of entries in XmNdropTransfers. If this resource is set to 0 at any time, the transfer is considered complete. The value of XmNtransferStatus determines the completion handshaking process.


Specifies a procedure of type XtSelectionCallbackProc that delivers the requested selection values. The widget argument passed to this procedure is the DropTransfer widget. The selection atom passed is _MOTIF_DROP. For additional information on selection callback procedures, see X Toolkit Intrinsics—C Language Interface.


Specifies the current status of the drop transfer. The client updates this value when the transfer ends and communicates the value to the initiator. The possible values are


The transfer succeeded.


The transfer failed.

Inherited Resources

DropTransfer inherits behavior and a resource from Object. For a complete description of this resource, refer to the Object reference page.

Object Resource Set
Name Class Type Default Access

XmNdestroyCallback XmCCallback XtCallbackList NULL C

Referenced By

XmDragContext(3), XmDragIcon(3), XmDropSite(3), XmDropTransferAdd(3), XmDropTransferStart(3).