Tribblix: manual page: XmDragContext.3

XmDragContext(library call) XmDragContext(library call)

NAME

XmDragContext -- The DragContext widget class

SYNOPSIS

#include <Xm/DragDrop.h>

DESCRIPTION

DragContexts are special widgets used in drag and drop transactions.
A DragContext is implemented as a widget, but a client does not
explicitly create a DragContext widget. Instead, a client initiates a
drag and drop transaction by calling XmDragStart, and this routine
initializes and returns a DragContext widget. There is a unique
DragContext for each drag operation. The toolkit frees a DragContext
when a transaction is complete; therefore, an application programmer
should not explicitly destroy a DragContext.

Initiator and receiver clients both use DragContexts to track the
state of a transaction. When the initiator and receiver of a
transaction are in the same client, they share the same DragContext
instance. If they are in different clients, there are two separate
DragContexts. In this case, the initiator calls XmDragStart and the
toolkit provides a DragContext for the receiver client. The only
resources pertinent to the receiver are XmNexportTargets and
XmNnumExportTargets. These can both be passed as arguments to the
XmDropSiteRetrieve function to obtain information about the current
drop site.

In general, in order to receive data, a drop site must share at least
one target type and operation in common with a drag source. The
DragContext resource, XmNexportTargets, identifies the selection
targets for the drag source. These export targets are compared with
the XmNimportTargets resource list specified by a drop site. The
DragContext resource, XmNdragOperations, identifies the valid
operations that can be applied to the source data by the initiator.
The drop site counterpart resource is XmNdropSiteOperations, which
indicates a drop site's supported operations.

A client uses DragIcon widgets to define the drag-over animation
effects associated with a given drag and drop transaction. An
initiator specifies a set of drag icons, selects a blending model,
and sets foreground and background cursor colors with DragContext
resources.

The type of drag-over visual used to represent a drag operation
depends on the drag protocol style. In preregister mode, the server
is grabbed, and either a cursor or a pixmap may be used as a drag-
over visual. In dynamic mode, drag-over visuals must be implemented
with the X cursor. If the resulting drag protocol style is Drop Only
or None and the XmNdragInitiatorProtocolStyle is XmDRAG_DYNAMIC or
XmDRAG_PREFER_DYNAMIC, then a dynamic visual style (cursor) is used.
Otherwise, a preregister visual style is used.

Classes

DragContext inherits behavior and resources from Core.

The class pointer is xmDragContextClass.

The class name is XmDragContext.

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).

+-----------------------------------------------------------------------------------------------------------------------+
| XmDragContext Resource Set |
|Name | Class | Type | Default | Access |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNblendModel | XmCBlendModel | unsigned char | XmBLEND_ALL | CG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNclientData | XmCClientData | XtPointer | NULL | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNconvertProc | XmCConvertProc | XtConvertSelectionIncrProc | NULL | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNcursorBackground | XmCCursorBackground | Pixel | dynamic | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNcursorForeground | XmCCursorForeground | Pixel | dynamic | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNdragDropFinishCallback | XmCCallback | XtCallbackList | NULL | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNdragMotionCallback | XmCCallback | XtCallbackList | NULL | C |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNdragOperations | XmCDragOperations | unsigned char | XmDROP_COPY | XmDROP_MOVE | C |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNdropFinishCallback | XmCCallback | XtCallbackList | NULL | C |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNdropSiteEnterCallback | XmCCallback | XtCallbackList | NULL | C |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNdropSiteLeaveCallback | XmCCallback | XtCallbackList | NULL | C |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNdropStartCallback | XmCCallback | XtCallbackList | NULL | C |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNexportTargets | XmCExportTargets | Atom * | NULL | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNincremental | XmCIncremental | Boolean | False | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNinvalidCursorForeground | XmCCursorForeground | Pixel | dynamic | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNnoneCursorForeground | XmCCursorForeground | Pixel | dynamic | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNnumExportTargets | XmCNumExportTargets | Cardinal | 0 | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNoperationChangedCallback | XmCCallback | XtCallbackList | NULL | C |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNoperationCursorIcon | XmCOperationCursorIcon | Widget | dynamic | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNsourceCursorIcon | XmCSourceCursorIcon | Widget | dynamic | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNsourcePixmapIcon | XmCSourcePixmapIcon | Widget | dynamic | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNstateCursorIcon | XmCStateCursorIcon | Widget | dynamic | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNtopLevelEnterCallback | XmCCallback | XtCallbackList | NULL | C |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNtopLevelLeaveCallback | XmCCallback | XtCallbackList | NULL | C |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
|XmNvalidCursorForeground | XmCCursorForeground | Pixel | dynamic | CSG |
+----------------------------+------------------------+----------------------------+---------------------------+--------+
+----------------------------+------------------------+----------------------------+---------------------------+--------+
XmNblendModel
Specifies which combination of DragIcons are blended to
produce a drag-over visual.

XmBLEND_ALL
Blends all three DragIcons: the source, state and
operation icons. The icons are layered from top
to bottom with the operation icon on top and the
source icon on the bottom. The hotspot is
derived from the state icon.

XmBLEND_STATE_SOURCE
Blends the state and source icons only. The
hotspot is derived from the state icon.

XmBLEND_JUST_SOURCE
Specifies that only the source icon is used,
which the initiator updates as required.

XmBLEND_NONE
Specifies that no drag-over visual is generated.
The client tracks the drop site status through
callback routines and updates the drag-over
visuals as necessary.

XmNclientData
Specifies the client data to be passed to XmNconvertProc
when it is invoked.

XmNconvertProc
If XmNincremental is True, specifies a procedure of type
XtConvertSelectionIncrProc that converts the source data to
the format(s) requested by the receiver client. The widget
argument passed to this procedure is the DragContext
widget. The selection atom passed is _MOTIF_DROP. If
XmNincremental is False, the procedure is an
XtConvertSelectionProc, and should ignore the max_length,
client_data, and request_id arguments and should handle the
conversion atomically. Data returned by XmNconvertProc
must be allocated using XtMalloc, and will be freed
automatically by the toolkit after the transfer. For
additional information on selection conversion procedures,
see X Toolkit Intrinsics--C Language Interface.

XmNcursorBackground
Specifies the background pixel value of the cursor.

XmNcursorForeground
Specifies the foreground pixel value of the cursor when the
state icon is not blended. This resource defaults to the
foreground color of the widget passed to the XmDragStart
function.

XmNdragDropFinishCallback
Specifies the list of callbacks that are called when the
transaction is completed. The type of the structure whose
address is passed to this callback is
XmDragDropFinishCallbackStruct. The reason sent by the
callback is XmCR_DRAG_DROP_FINISH.

XmNdragMotionCallback
Specifies the list of callbacks that are invoked when the
pointer moves. The type of structure whose address is
passed to this callback is XmDragMotionCallbackStruct. The
reason sent by the callback is XmCR_DRAG_MOTION.

XmNdragOperations
Specifies the set of valid operations associated with an
initiator client for a drag transaction. This resource is
a bit mask that is formed by combining one or more of the
following values using a bitwise operation such as
inclusive OR (|): XmDROP_COPY, XmDROP_LINK, XmDROP_MOVE.
The value XmDROP_NOOP for this resource indicates that no
operations are valid. For Text and TextField widgets, this
resource is set to XmDROP_COPY | XmDROP_MOVE; for List
widgets, it is set to XmDROP_COPY.

XmNdropFinishCallback
Specifies the list of callbacks that are invoked when the
drop is completed. The type of the structure whose address
is passed to this callback is XmDropFinishCallbackStruct.
The reason sent by the callback is XmCR_DROP_FINISH.

XmNdropSiteEnterCallback
Specifies the list of callbacks that are invoked when the
pointer enters a drop site. The type of the structure whose
address is passed to this callback is
XmDropSiteEnterCallbackStruct. The reason sent by the
callback is XmCR_DROP_SITE_ENTER.

XmNdropSiteLeaveCallback
Specifies the list of callbacks that are invoked when the
pointer leaves a drop site. The type of the structure whose
address is passed to this callback is
XmDropSiteLeaveCallbackStruct. The reason sent by the
callback is XmCR_DROP_SITE_LEAVE.

XmNdropStartCallback
Specifies the list of callbacks that are invoked when a
drop is initiated. The type of the structure whose address
is passed to this callback is XmDropStartCallbackStruct.
The reason sent by the callback is XmCR_DROP_START.

XmNexportTargets
Specifies the list of target atoms associated with this
source. This resource identifies the selection targets
this source can be converted to.

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

XmNinvalidCursorForeground
Specifies the foreground pixel value of the cursor when the
state is invalid. This resource defaults to the value of
the XmNcursorForeground resource.

XmNnoneCursorForeground
Specifies the foreground pixel value of the cursor when the
state is none. This resource defaults to the value of the
XmNcursorForeground resource.

XmNnumExportTargets
Specifies the number of entries in the list of export
targets.

XmNoperationChangedCallback
Specifies the list of callbacks that are invoked when the
drag is started and when the user requests that a different
operation be applied to the drop. The type of the
structure whose address is passed to this callback is
XmOperationChangedCallbackStruct. The reason sent by the
callback is XmCR_OPERATION_CHANGED.

XmNoperationCursorIcon
Specifies the cursor icon used to designate the type of
operation performed by the drag transaction. If NULL,
XmScreen resources provide default icons for copy, link,
and move operations.

XmNsourceCursorIcon
Specifies the cursor icon used to represent the source when
a dynamic visual style is used. If NULL, the
XmNdefaultSourceCursorIcon resource of XmScreen provides a
default cursor icon.

XmNsourcePixmapIcon
Specifies the pixmap icon used to represent the source when
a preregister visual style is used. The icon is used in
conjunction with the colormap of the widget passed to
XmDragStart. If NULL, XmNsourceCursorIcon is used.

XmNstateCursorIcon
Specifies the cursor icon used to designate the state of a
drop site. If NULL, XmScreen resources provide default
icons for a valid, invalid, and no drop site condition.

XmNtopLevelEnterCallback
Specifies the list of callbacks that are called when the
pointer enters a top-level window or root window (due to
changing screens). The type of the structure whose address
is passed to this callback is
XmTopLevelEnterCallbackStruct. The reason sent by the
callback is XmCR_TOP_LEVEL_ENTER.

XmNtopLevelLeaveCallback
Specifies the list of callbacks that are called when the
pointer leaves a top level window or the root window (due
to changing screens). The type of the structure whose
address is passed to this callback is
XmTopLevelLeaveCallbackStruct. The reason sent by the
callback is XmCR_TOP_LEVEL_LEAVE.

XmNvalidCursorForeground
Specifies the foreground pixel value of the cursor
designated as a valid cursor icon.

Inherited Resources

Callback Information

Each of the DragContext callbacks has an associated callback
structure.

A pointer to the following structure is passed to the
XmNdragDropFinishCallback callback:

typedef struct
{
int reason;
XEvent *event;
Time timeStamp;
}XmDragDropFinishCallbackStruct, *XmDragDropFinishCallback;

reason Indicates why the callback was invoked

event Points to the XEvent that triggered the callback

timeStamp Specifies the time at which either the drag or the drop was
completed

A pointer to the following structure is passed to callbacks for
XmNdragMotionCallback:

typedef struct
{
int reason;
XEvent *event;
Time timeStamp;
unsigned char operation;
unsigned char operations;
unsigned char dropSiteStatus;
Position x;
Position y;
}XmDragMotionCallbackStruct, *XmDragMotionCallback;

reason Indicates why the callback was invoked.

event Points to the XEvent that triggered the callback.

timeStamp Specifies the timestamp of the logical event.

operation Identifies an operation.

If the toolkit has just called a DropSite's XmNdragProc,
the toolkit initializes operation to the value of the
operation member of the XmDragProcCallbackStruct at the
time the DropSite's XmNdragProc returns.

If the toolkit has not called an XmNdragProc and the
pointer is within an active drop site, the toolkit
initializes operation by selecting an operation from the
bitwise AND of the initial value of the operations member
and the value of the DropSite's XmNdropSiteOperations
resource. The toolkit searches this set first for
XmDROP_MOVE, then for XmDROP_COPY, then for XmDROP_LINK,
and initializes operation to the first operation it finds
in the set. If the toolkit finds none of these operations
in the set, it initializes operation to XmDROP_NOOP.

If the toolkit has not called an XmNdragProc and the
pointer is not within an active drop site, the toolkit
initializes operation by selecting an operation from the
initial value of the operations member. The toolkit
searches this set first for XmDROP_MOVE, then for
XmDROP_COPY, then for XmDROP_LINK, and initializes
operation to the first operation it finds in the set. If
the toolkit finds none of these operations in the set, it
initializes operation to XmDROP_NOOP.

operations
Indicates the set of operations supported for the source
data.

If the toolkit has just called a DropSite's XmNdragProc,
the toolkit initializes operations to the bitwise AND of
the DropSite's XmNdropOperations and the value of the
operations member of the XmDragProcCallbackStruct at the
time the DropSite's XmNdragProc returns. If the resulting
set of operations is empty, the toolkit initializes
operations to XmDROP_NOOP.

If the toolkit has not called an XmNdragProc and the user
does not select an operation (by pressing a modifier key),
the toolkit initializes operations to the value of the
DragContext's XmNdragOperations resource.

If the toolkit has not called an XmNdragProc and the user
does select an operation, the toolkit initializes
operations to the bitwise AND of the corresponding
operation and the value of the DragContext's
XmNdragOperations resource. If the resulting set of
operations is empty, the toolkit initializes operations to
XmDROP_NOOP.

dropSiteStatus
Indicates whether or not a drop site is valid.

If the toolkit has just called a DropSite's XmNdragProc,
the toolkit initializes dropSiteStatus to the value of the
dropSiteStatus member of the XmDragProcCallbackStruct at
the time the DropSite's XmNdragProc returns.

If the toolkit has not called an XmNdragProc, it
initializes dropSiteStatus as follows: the toolkit
initializes dropSiteStatus to XmNO_DROP_SITE if the pointer
is over an inactive drop site or is not over a drop site.
The toolkit initializes dropSiteStatus to XmDROP_SITE_VALID
if all the following conditions are met:

+o The pointer is over an active drop site.

+o The DragContext's XmNexportTargets and the DropSite's
XmNimportTargets are compatible.

+o The initial value of the operation member is not
XmDROP_NOOP.

Otherwise, the toolkit initializes dropSiteStatus to
XmDROP_SITE_INVALID.

A pointer to the following structure is passed for the
XmNdropFinishCallback callback:

typedef struct
{
int reason;
XEvent *event;
Time timeStamp;
unsigned char operation;
unsigned char operations;
unsigned char dropSiteStatus;
unsigned char dropAction;
unsigned char completionStatus;
}XmDropFinishCallbackStruct, *XmDropFinishCallback;

reason Indicates why the callback was invoked.

event Points to the XEvent that triggered the callback.

timeStamp Specifies the time at which the drop was completed.

operation Identifies an operation.

If the pointer is over an active drop site when the drop
begins, the toolkit initializes operation to the value of
the operation member of the XmDropProcCallbackStruct at the
time the DropSite's XmNdropProc returns.

If the pointer is not over an active drop site when the
drop begins, the toolkit initializes operation by selecting
an operation from the initial value of the operations
member. The toolkit searches this set first for
XmDROP_MOVE, then for XmDROP_COPY, then for XmDROP_LINK,
and initializes operation to the first operation it finds
in the set. If it finds none of these operations in the
set, it initializes operation to XmDROP_NOOP.

operations
Indicates the set of operations supported for the source
data.

If the pointer is over an active drop site when the drop
begins, the toolkit initializes operations to the bitwise
AND of the DropSite's XmNdropOperations and the value of
the operations member of the XmDropProcCallbackStruct at
the time the DropSite's XmNdropProc returns. If the
resulting set of operations is empty, the toolkit
initializes operations to XmDROP_NOOP.

If the pointer is not over an active drop site when the
drop begins and if the user does not select an operation
(by pressing a modifier key), the toolkit initializes
operations to the value of the DragContext's
XmNdragOperations resource.

If the pointer is not over an active drop site when the
drop begins and if the user does select an operation, the
toolkit initializes operations to the bitwise AND of the
corresponding operation and the value of the DragContext's
XmNdragOperations resource. If the resulting set of
operations is empty, the toolkit initializes operations to
XmDROP_NOOP.

dropSiteStatus
Indicates whether or not a drop site is valid.

If the pointer is over an active drop site when the drop
begins, the toolkit initializes dropSiteStatus to the value
of the dropSiteStatus member of the
XmDropProcCallbackStruct at the time the DropSite's
XmNdropProc returns.

If the pointer is not over an active drop site when the
drop begins, the toolkit initializes dropSiteStatus to
XmNO_DROP_SITE.

dropAction
Identifies the drop action. The values are XmDROP,
XmDROP_CANCEL, XmDROP_HELP, and XmDROP_INTERRUPT. The
XmDROP_INTERRUPT value is currently unsupported; if
specified, it will be interpreted as an XmDROP_CANCEL.

completionStatus
An IN/OUT member that indicates the status of the drop
action. After the last callback procedure has returned,
the final value of this member determines what visual
transition effects will be applied. There are two values:

XmDROP_SUCCESS
The drop was successful.

XmDROP_FAILURE
The drop was unsuccessful.

A pointer to the following structure is passed to callbacks for
XmNdropSiteEnterCallback:

typedef struct
{
int reason;
XEvent *event;
Time timeStamp;
unsigned char operation;
unsigned char operations;
unsigned char dropSiteStatus;
Position x;
Position y;
}XmDropSiteEnterCallbackStruct, *XmDropSiteEnterCallback;

reason Indicates why the callback was invoked.

event Points to the XEvent that triggered the callback.

timeStamp Specifies the time the crossing event occurred.

operation Identifies an operation.

If the toolkit has just called a DropSite's XmNdragProc,
the toolkit initializes operation to the value of the
operation member of the XmDragProcCallbackStruct at the
time the DropSite's XmNdragProc returns.

If the toolkit has not called an XmNdragProc, it
initializes operation by selecting an operation from the
bitwise AND of the initial value of the operations member
and the value of the DropSite's XmNdropSiteOperations
resource. The toolkit searches this set first for
XmDROP_MOVE, then for XmDROP_COPY, then for XmDROP_LINK,
and initializes operation to the first operation it finds
in the set. If the toolkit finds none of these operations
in the set, it initializes operation to XmDROP_NOOP.

operations
Indicates the set of operations supported for the source
data.

If the toolkit has just called a DropSite's XmNdragProc,
the toolkit initializes operations to the bitwise AND of
the DropSite's XmNdropOperations and the value of the
operations member of the XmDragProcCallbackStruct at the
time the DropSite's XmNdragProc returns. If the resulting
set of operations is empty, the toolkit initializes
operations to XmDROP_NOOP.

If the toolkit has not called an XmNdragProc and the user
does not select an operation (by pressing a modifier key),
the toolkit initializes operations to the value of the
DragContext's XmNdragOperations resource.

If the toolkit has not called an XmNdragProc and the user
does select an operation, the toolkit initializes
operations to the bitwise AND of the corresponding
operation and the value of the DragContext's
XmNdragOperations resource. If the resulting set of
operations is empty, the toolkit initializes operations to
XmDROP_NOOP.

dropSiteStatus
Indicates whether or not a drop site is valid.

If the toolkit has just called a DropSite's XmNdragProc,
the toolkit initializes dropSiteStatus to the value of the
dropSiteStatus member of the XmDragProcCallbackStruct at
the time the DropSite's XmNdragProc returns.

If the toolkit has not called XmNdragProc, it initializes
dropSiteStatus to XmDROP_SITE_VALID if the DragContext's
XmNexportTargets and the DropSite's XmNimportTargets are
compatible and if the initial value of the operation member
is not XmDROP_NOOP. Otherwise, the toolkit initializes
dropSiteStatus to XmDROP_SITE_INVALID.

x Indicates the x-coordinate of the pointer in root window
coordinates.

y Indicates the y-coordinate of the pointer in root window
coordinates.

A pointer to the following structure is passed to callbacks for
XmNdropSiteLeaveCallback:

typedef struct
{
int reason;
XEvent *event;
Time timeStamp;
}XmDropSiteLeaveCallbackStruct, *XmDropSiteLeaveCallback;

reason Indicates why the callback was invoked

event Points to the XEvent that triggered the callback

timeStamp Specifies the timestamp of the logical event

A pointer to the following structure is passed for the
XmNdropStartCallback callback:

typedef struct
{
int reason;
XEvent *event;
Time timeStamp;
unsigned char operation;
unsigned char operations;
unsigned char dropSiteStatus;
unsigned char dropAction;
Position x;
Position y;
}XmDropStartCallbackStruct, *XmDropStartCallback;

reason Indicates why the callback was invoked.

event Points to the XEvent that triggered the callback.

timeStamp Specifies the time at which the drag was completed.

operation Identifies an operation.

If the pointer is over an active drop site when the drop
begins, the toolkit initializes operation to the value of
the operation member of the XmDropProcCallbackStruct at the
time the DropSite's XmNdropProc returns.

If the pointer is not over an active drop site when the
drop begins, the toolkit initializes operation by selecting
an operation from the initial value of the operations
member. The toolkit searches this set first for
XmDROP_MOVE, then for XmDROP_COPY, then for XmDROP_LINK,
and initializes operation to the first operation it finds
in the set. If it finds none of these operations in the
set, it initializes operation to XmDROP_NOOP.

operations
Indicates the set of operations supported for the source
data.

If the pointer is over an active drop site when the drop
begins, the toolkit initializes operations to the bitwise
AND of the DropSite's XmNdropOperations and the value of
the operations member of the XmDropProcCallbackStruct at
the time the DropSite's XmNdropProc returns. If the
resulting set of operations is empty, the toolkit
initializes operations to XmDROP_NOOP.

If the pointer is not over an active drop site when the
drop begins and if the user does not select an operation
(by pressing a modifier key), the toolkit initializes
operations to the value of the DragContext's
XmNdragOperations resource.

If the pointer is not over an active drop site when the
drop begins and if the user does select an operation, the
toolkit initializes operations to the bitwise AND of the
corresponding operation and the value of the DragContext's
XmNdragOperations resource. If the resulting set of
operations is empty, the toolkit initializes operations to
XmDROP_NOOP.

dropSiteStatus
Indicates whether or not a drop site is valid.

If the pointer is over an active drop site when the drop
begins, the toolkit initializes dropSiteStatus to the value
of the dropSiteStatus member of the
XmDropProcCallbackStruct at the time the DropSite's
XmNdropProc returns.

If the pointer is not over an active drop site when the
drop begins, the toolkit initializes dropSiteStatus to
XmNO_DROP_SITE.

This field is invalid if the dropAction field is set to
XmDROP_CANCEL.

dropAction
An IN/OUT member that identifies the drop action. The
values are XmDROP, XmDROP_CANCEL, XmDROP_HELP, and
XmDROP_INTERRUPT. The value of dropAction can be modified
to change the action actually initiated. The value
XmDROP_INTERRUPT is currently unsupported; if specified, it
will be interpreted as an XmDROP_CANCEL.

x Indicates the x-coordinate of the pointer in root window
coordinates.

y Indicates the y-coordinate of the pointer in root window
coordinates.

A pointer to the following structure is passed to the
XmNoperationChangedCallback callback:

typedef struct
{
int reason;
XEvent *event;
Time timeStamp;
unsigned char operation;
unsigned char operations;
unsigned char dropSiteStatus;
}XmOperationChangedCallbackStruct, *XmOperationChangedCallback;

reason Indicates why the callback was invoked.

event Points to the XEvent that triggered the callback.

timeStamp Specifies the time at which the crossing event occurred.

operation Identifies an operation.

If the toolkit has just called a DropSite's XmNdragProc,
the toolkit initializes operation to the value of the
operation member of the XmDragProcCallbackStruct at the
time the DropSite's XmNdragProc returns.

If the toolkit has not called an XmNdragProc, and the
pointer is within an active drop site, the toolkit
initializes operation by selecting an operation from the
bitwise AND of the initial value of the operations member
and the value of the DropSite's XmNdropSiteOperations
resource. The toolkit searches this set first for
XmDROP_MOVE, then for XmDROP_COPY, then for XmDROP_LINK,
and initializes operation to the first operation it finds
in the set. If the toolkit finds none of these operations
in the set, it initializes operation to XmDROP_NOOP.

If the toolkit has not called an XmNdragProc, and the
pointer is not within an active drop site, the toolkit
initializes operation by selecting an operation from the
initial value of the operations member. The toolkit
searches this set first for XmDROP_MOVE, then for
XmDROP_COPY, then for XmDROP_LINK, and initializes
operation to the first operation it finds in the set. If
the toolkit finds none of these operations in the set, it
initializes operation to XmDROP_NOOP.

operations
Indicates the set of operations supported for the source
data.

If the toolkit has just called a DropSite's XmNdragProc,
the toolkit initializes operations to the bitwise AND of
the DropSite's XmNdropOperations and the value of the
operations member of the XmDragProcCallbackStruct at the
time the DropSite's XmNdragProc returns. If the resulting
set of operations is empty, the toolkit initializes
operations to XmDROP_NOOP.

If the toolkit has not called an XmNdragProc, and the user
does not select an operation (by pressing a modifier key),
the toolkit initializes operations to the value of the
DragContext's XmNdragOperations resource.

If the toolkit has not called an XmNdragProc, and the user
does select an operation, the toolkit initializes
operations to the bitwise AND of the corresponding
operation and the value of the DragContext's
XmNdragOperations resource. If the resulting set of
operations is empty, the toolkit initializes operations to
XmDROP_NOOP.

dropSiteStatus
Indicates whether or not a drop site is valid.

If the toolkit has just called a DropSite's XmNdragProc,
the toolkit initializes dropSiteStatus to the value of the
dropSiteStatus member of the XmDragProcCallbackStruct at
the time the DropSite's XmNdragProc returns.

If the toolkit has not called an XmNdragProc it initializes
dropSiteStatus to XmNO_DROP_SITE if the pointer is over an
inactive drop site or is not over a drop site. The toolkit
initializes dropSiteStatus to XmDROP_SITE_VALID if all the
following conditions are met:

+o The pointer is over an active drop site

+o The DragContext's XmNexportTargets and the DropSite's
XmNimportTargets are compatible

+o The initial value of the operation member is not
XmDROP_NOOP

Otherwise, the toolkit initializes dropSiteStatus to
XmDROP_SITE_INVALID.

A pointer to the following structure is passed to callbacks for
XmNtopLevelEnterCallback:

typedef struct
{
int reason;
XEvent *event;
Time timeStamp;
Screen screen;
Window window;
Position x;
Position y;
unsigned char dragProtocolStyle;
}XmTopLevelEnterCallbackStruct, *XmTopLevelEnterCallback;

reason Indicates why the callback was invoked.

event Points to the XEvent that triggered the callback.

timeStamp Specifies the timestamp of the logical event.

screen Specifies the screen associated with the top-level window
or root window being entered.

window Specifies the ID of the top-level window or root window
being entered.

x Indicates the x-coordinate of the pointer in root window
coordinates.

y Indicates the y-coordinate of the pointer in root window
coordinates.

dragProtocolStyle
Specifies the protocol style adopted by the initiator. The
values are XmDRAG_DROP_ONLY, XmDRAG_DYNAMIC, XmDRAG_NONE,
and XmDRAG_PREREGISTER.

A pointer to the following structure is passed to callbacks for
XmNtopLevelLeaveCallback:

typedef struct
{
int reason;
XEvent *event;
Time timeStamp;
Screen screen;
Window window;
}XmTopLevelLeaveCallbackStruct, *XmTopLevelLeaveCallback;

reason Indicates why the callback was invoked

event Points to the XEvent that triggered the callback

timeStamp Specifies the timestamp of the logical event

screen Specifies a screen associated with the top-level window or
root window being left

window Specifies the ID of the top-level window or root window
being left

Translations

The XmDragContext translations are described in the following list.
The following key names are listed in the X standard key event
translation table syntax. This format is the one used by Motif to
specify the widget actions corresponding to a given key. A brief
overview of the format is provided under VirtualBindings(3). For a
complete description of the format, please refer to the X Toolkit
Instrinsics Documentation.

Button1<Enter>:
DragMotion()

Button1<Leave>:
DragMotion()

Button1<Motion>:
DragMotion()

Button2<Enter>:
DragMotion()

Button2<Leave>:
DragMotion()

Button2<Motion>:
DragMotion()

<Btn2Up>: FinishDrag()

<Btn1Up>: FinishDrag()

<Key>Return:
FinishDrag()

<Key><osfActivate>:
FinishDrag()

<BtnDown>:
IgnoreButtons()

<BtnUp>: IgnoreButtons()

:<Key><osfCancel>:
CancelDrag()

:<Key><osfHelp>:
HelpDrag()

:<Key><osfUp>:
DragKey(Up)

:<Key><osfDown>:
DragKey(Down)

:<Key><osfLeft>:
DragKey(Left)

:<Key><osfRight>:
DragKey(Right)

:<KeyUp>: DragKey(Update)

:<KeyDown>:
DragKey(Update)

Action Routines

The XmDragContext action routines are

CancelDrag():
Cancels the drag operation and frees the associated
DragContext.

DragKey(String)
If the value of String is Left, Right, Up, or Down, this
action moves the dragged object in the corresponding
location. Any other values of String are ignored.

DragMotion():
Drags the selected data as the pointer is moved.

FinishDrag():
Finishes the drag operation and starts the drop operation.

HelpDrag():
Initiates a conditional drop that enables the receiver to
provide help information to the user. The user can cancel
or continue the drop operation in response to this
information.

Virtual Bindings

The bindings for virtual keys are vendor specific. For information
about bindings for virtual buttons and keys, see VirtualBindings(3).

RELATED INFORMATION

Core(3), XmDisplay(3), XmDragCancel(3), XmDragIcon(3),
XmDragStart(3), XmDropSite(3), XmDropTransfer(3), and XmScreen(3).

XmDragContext(library call)