XmDisplay(X3mot)

XmDisplay -- the Display widget class

Synopsis

#include <Xm/Display.h>

Description

The XmDisplay object is used by the Motif widgets to store information that is specific to a display. It also allows the toolkit to access certain information on widget hierarchies that would otherwise be unavailable. Each client has one XmDisplay object for each display it accesses.

An XmDisplay object is automatically created when the application creates the first shell on a display (usually accomplished by a call to XtAppInitialize or XtAppCreateShell). It is not necessary to create an XmDisplay object by any other means. An application can use the function XmGetXmDisplay to obtain the widget ID of the XmDisplay object for a given display.

An application cannot supply initial values for XmDisplay resources as arguments to a call to any function that creates widgets. The application or user can supply initial values in a resource file. After creating the first shell on the display, the application can use XmGetXmDisplay to obtain the widget ID of the XmDisplay object and then call XtSetValues to set the XmDisplay resources.

XmDisplay resources specify the drag protocol style for a client participating in drag and drop transactions. There are two basic protocol types, preregister and dynamic. When a preregister protocol is used, the toolkit handles any communication between the initiator and receiver clients, and displays the appropriate drag-over and drag-under visual effects. A client registers its drop sites in advance and this information is stored in a property for each top-level window. When the drag pointer enters a top level window, the drop site information is read by the initiator. A dynamic protocol allows the source and destination clients to dynamically communicate drag and drop state information between each other, and to update their respective visuals accordingly. The toolkit provides drop site information as the pointer passes over any given drop site. In this mode, a receiver can supply a procedure to generate its own drag-under effects.

Classes

Display inherits behavior and resources from Core, Composite, Shell, WMShell, VendorShell, TopLevelShell, and ApplicationShell classes.

The class pointer is xmDisplayClass.

The class name is XmDisplay.

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 an .Xdefaults file, remove the ``XmN'' or ``XmC'' prefix and use the remaining letters. To specify one of the defined values for a resource in an .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).

XmDisplay resource set

Name Class Type Default Access

XmNdefaultVirtualBindings DefaultVirtualBindings String dynamic CG

XmNdragInitiatorProtocolStyle XmCDragInitiatorProtocolStyle unsigned char XmDRAG_PREFER_RECEIVER

CG

XmNdragReceiverProtocolStyle XmCDragReceiverProtocolStyle unsigned char XmDRAG_PREFER_PREREGISTER

CG

Name	Class	Type	Default	Access
XmNdefaultVirtualBindings	DefaultVirtualBindings	String	dynamic	CG
XmNdragInitiatorProtocolStyle	XmCDragInitiatorProtocolStyle	unsigned	char	XmDRAG_PREFER_RECEIVER
CG
XmNdragReceiverProtocolStyle	XmCDragReceiverProtocolStyle	unsigned	char	XmDRAG_PREFER_PREREGISTER
CG

 
 ------------------------------------------------------------------------------------------------------------------- 
| Name                         |  Class                        |  Type     |  Default  |  Access                   | 
|------------------------------|-------------------------------|-----------|-----------|---------------------------| 
| XmNdefaultVirtualBindings    |  DefaultVirtualBindings       |  String   |  dynamic  |  CG                       | 
|------------------------------|-------------------------------|-----------|-----------|---------------------------| 
| XmNdragInitiatorProtocolStyle|  XmCDragInitiatorProtocolStyle|  unsigned |  char     |  XmDRAG_PREFER_RECEIVER   | 
|------------------------------|-------------------------------|-----------|-----------|---------------------------| 
| XmNdragReceiverProtocolStyle |  XmCDragReceiverProtocolStyle |  unsigned |  char     |  XmDRAG_PREFER_PREREGISTER| 
|------------------------------|-------------------------------|-----------|-----------|---------------------------|

XmNdefaultVirtualBindings

Specifies the default virtual bindings for the display. Following is an example of a specification for the defaultVirtualBindings resource in a resource file:

*defaultVirtualBindings: \ 
	osfBackSpace	:	<Key>BackSpace	\n\ 
	osfInsert	:	<Key>InsertChar	\n\ 
... 
	osfDelete	:	<Key>DeleteChar

XmNdragInitiatorProtocolStyle

Specifies the drag and drop protocol requirements or preference when the client is an initiator. The possible values are:

XmDRAG_PREREGISTER -- as an initiator, this client does not use the dynamic protocol and can only arrange visual effects with receivers who provide preregistered information.
XmDRAG_DYNAMIC -- as an initiator, this client does not make use of any preregistered drop site information made available by other clients, and can only arrange visual effects with receivers who use the dynamic protocol.
XmDRAG_NONE -- specifies that drag and drop is disabled for this client.
XmDRAG_DROP_ONLY -- as an initiator, this client does not use either the preregistered drop site information or the dynamic protocol. It supports dragging, and any time the cursor is over a client that supports drag and drop, valid feedback is provided. There are no other visual effects.
XmDRAG_PREFER_DYNAMIC -- as an initiator, this client can support both the preregister and dynamic protocols, but prefers to use dynamic protocols whenever possible in order to provide high-quality drag-under feedback.
XmDRAG_PREFER_PREREGISTER -- as an initiator, this client can support both the preregister and dynamic protocols, but prefers to use the preregister protocol whenever possible in order to accommodate performance needs or to provide consistent drag-over feedback.
XmDRAG_PREFER_RECEIVER -- indicates that this client can support both preregister and dynamic protocols, but will defer to the preference of the receiver client. This value is valid only for the XmNdragInitiatorProtocolStyle resource, and is its default value.

XmNdragReceiverProtocolStyle

Specifies the drag and drop protocol requirements or preference when this client is a receiver. The values are:

XmDRAG_PREREGISTER -- as a receiver, this client preregisters drop site information and does not use the dynamic protocol. It can only arrange visual effects with initiators who make use of the preregistered information.
XmDRAG_DYNAMIC -- as a receiver, this client uses the dynamic protocol and does not preregister drop site information. It can only arrange visual effects with initiators who use the dynamic protocol.
XmDRAG_NONE -- specifies that drag and drop is disabled for this client.
XmDRAG_DROP_ONLY -- as a receiver, this client neither uses the dynamic protocol nor preregisters drop site information. It supports dropping, and when dragging over this client, valid feedback is always provided, but there are no other visual effects.
XmDRAG_PREFER_DYNAMIC -- as a receiver, this client can support both the preregister and dynamic protocols, but prefers to use dynamic protocol whenever possible in order to provide high-quality drag-under feedback.
XmDRAG_PREFER_PREREGISTER -- as a receiver, this client can support both the preregister and dynamic protocols, but prefers to use the preregister protocol whenever possible in order to accommodate performance needs.

The actual protocol used between an initiator and a receiver is based on the protocol style of the receiver and initiator. The decision matrix is as follows:

Drag initiator Drag receiver protocol style

protocol style Preregister Prefer Preregister Prefer Dynamic Dynamic

Preregister Preregister Preregister Preregister Drop only

Prefer Preregister Preregister Preregister Preregister Dynamic

Prefer Receiver Preregister Preregister Dynamic Dynamic

Prefer Dynamic Preregister Dynamic Dynamic Dynamic

Dynamic Drop only Dynamic Dynamic Dynamic

Drag initiator	Drag receiver protocol style
protocol style	Preregister	Prefer Preregister	Prefer Dynamic	Dynamic
Preregister	Preregister	Preregister	Preregister	Drop only
Prefer Preregister	Preregister	Preregister	Preregister	Dynamic
Prefer Receiver	Preregister	Preregister	Dynamic	Dynamic
Prefer Dynamic	Preregister	Dynamic	Dynamic	Dynamic
Dynamic	Drop only	Dynamic	Dynamic	Dynamic

 
 ------------------------------------------------------------------------------------ 
| Drag initiator    |                  Drag receiver protocol style                 | 
|-------------------|-------------|--------------------|----------------|-----------| 
|                   | ------------|--------------------|----------------|-----------| 
|-------------------|-------------|--------------------|----------------|-----------| 
| protocol style    |  Preregister|  Prefer Preregister|  Prefer Dynamic|  Dynamic  | 
|-------------------|-------------|--------------------|----------------|-----------| 
| Preregister       |  Preregister|  Preregister       |  Preregister   |  Drop only| 
|-------------------|-------------|--------------------|----------------|-----------| 
| Prefer Preregister|  Preregister|  Preregister       |  Preregister   |  Dynamic  | 
|-------------------|-------------|--------------------|----------------|-----------| 
| Prefer Receiver   |  Preregister|  Preregister       |  Dynamic       |  Dynamic  | 
|-------------------|-------------|--------------------|----------------|-----------| 
| Prefer Dynamic    |  Preregister|  Dynamic           |  Dynamic       |  Dynamic  | 
|-------------------|-------------|--------------------|----------------|-----------| 
| Dynamic           |  Drop only  |  Dynamic           |  Dynamic       |  Dynamic  | 
|-------------------|-------------|--------------------|----------------|-----------|

The value XmDRAG_NONE does not appear in the above matrix. When specified for either the initiator or receiver side, XmDRAG_NONE implies that drag and drop transactions are not supported. A value of XmDRAG_DROP_ONLY (Drop Only) results when an initiator and receiver cannot compromise protocol styles, that is, one client requires dynamic mode while the other can only support preregister mode, or if either explicitly has specified XmDRAG_DROP_ONLY.

Inherited resources

All of the superclass resources inherited by XmDisplay are designated N/A (not applicable).

References

ApplicationShell(X3mot), Composite(X3mot), Core(X3mot), TopLevelShell(X3mot), VendorShell(X3mot), WMShell(X3mot), XmGetXmDisplay(X3mot) and XmScreen(X3mot).