XmDropSite(3)

NAME
XmDropSite — The DropSite Registry

SYNOPSIS

#include <Xm/DragDrop.h>

DESCRIPTION

A client registers a widget or gadget as a drop site using the XmDropSiteRegister function. In addition, this routine defines the behavior and capabilities of a drop site by specifying appropriate resources. For example, the XmNimportTargets and XmNnumImportTargets resources identify respectively the selection target types and number of types supported by a drop site. The visual animation effects associated with a drop site are also described with DropSite resources.

Drop site animation effects that occur in response to the pointer entering a valid drop site are called drag-under effects. A receiver can select from several animation styles supplied by the toolkit or can provide customized animation effects. Drag-under effects supplied by the toolkit include border highlighting, shadow in/out drawing, and pixmap representation.

When a preregister drag protocol style is used, the toolkit generates drag-under visual effects based on the value of the XmNanimationStyle resource. In dynamic mode, if the drop site XmNdragProc resource is NULL, the toolkit also provides animation effects based on the XmNanimationStyle resource. Otherwise, if the XmNdragProc routine is specified, the receiver can either assume responsibility for animation effects (through the XmNdragProc routine) or rely on the toolkit to provide animation. An application can either handle all or none of the animation effects for a particular drop site. That is, an application should never do a partial job of animation on a particular drop site.

Drop sites may overlap. The initial stacking order corresponds to the order in which the drop sites were registered. When a drop site overlaps another drop site, the drag-under effects of the drop site underneath are clipped by the obscuring drop site(s).

The XmDropSiteUpdate routine sets resources for a widget that is registered as a drop site. XmDropSiteRetrieve gets drop site resource values previously specified for a registered widget. These routines are used instead of XtSetValues and XtGetValues.

  Classes

XmDropSite does not inherit from any widget class.

  New Resources

The following table defines a set of widget resources used by the programmer to specify data. 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 XmDropSiteUpdate (S), retrieved by using XmDropSiteRetrieve (G), or is not applicable (N/A).

XmNanimationMask
    Specifies a mask to use with the pixmap specified by XmNanimationPixmap when the animation style is XmDRAG_UNDER_PIXMAP.

XmNanimationPixmap
    Specifies a pixmap for drag-under animation when the animation style is XmDRAG_UNDER_PIXMAP. The pixmap is drawn with its origin at the upper left corner of the bounding box of the drop site. If the drop site window is larger than the animation pixmap, the portion of the window not covered by the pixmap will be tiled with the window's background color.

XmNanimationPixmapDepth
    Specifies the depth of the pixmap specified by the XmNanimationPixmap resource. When the depth is 1, the colors are taken from the foreground and background of the drop site widget. For any other value, drop site animation occurs only if the XmNanimationPixmapDepth matches the depth of the drop site window. Colors are derived from the current colormap.

XmNanimationStyle
    Specifies the drag-under animation style used when a drag enters a valid drop site. The possible values are

    XmDRAG_UNDER_HIGHLIGHT
        The drop site uses highlighting effects.

    XmDRAG_UNDER_SHADOW_OUT
        The drop site uses an outset shadow.

    XmDRAG_UNDER_SHADOW_IN
        The drop site uses an inset shadow.

    XmDRAG_UNDER_PIXMAP
        The drop site uses the pixmap specified by XmNanimationPixmap to indicate that it can receive the drop.

    XmDRAG_UNDER_NONE
        The drop site does not use animation effects. A client using a dynamic protocol, may provide drag-under effects in its XmNdragProc routine.

XmNdragProc
    Specifies the procedure that is invoked when the drop site receives a crossing, motion, or operation changed message. This procedure is called only when a dynamic protocol is used. The type of structure whose address is passed to this procedure is XmDragProcCallbackStruct. The reason sent to the procedure is one of the following:

    •   XmCR_DROP_SITE_ENTER_MESSAGE

    •   XmCR_DROP_SITE_LEAVE_MESSAGE

    •   XmCR_DRAG_MOTION

    •   XmCR_OPERATION_CHANGED

    The drag procedure may change the values of some members of the XmDragProcCallbackStruct passed to it. After the drag procedure returns, the toolkit uses the final values in initializing some members of the callback structure passed to the appropriate callbacks of the initiator (the DragContext's XmNdropSiteEnterCallback, XmNdropSiteLeaveCallback, XmNdragMotionCallback, or XmNoperationChangedCallback callbacks).

XmNdropProc
    Specifies the procedure that is invoked when a drop (excluding a cancel or interrupt action) occurs on a drop site regardless of the status of the drop site. The type of the structure whose address is passed to this procedure is XmDropProcCallbackStruct. The reason sent to the procedure is XmCR_DROP_MESSAGE.

    The drop procedure may change the values of some members of the XmDropProcCallbackStruct passed to it. After the drop procedure returns, the toolkit uses the final values in initializing some members of the XmDropStartCallbackStruct passed to the initiator's drop start callbacks (the DragContext's XmNdropStartCallback callbacks).

XmNdropRectangles
    Specifies a list of rectangles that describe the shape of a drop site. The locations of the rectangles are relative to the origin of the enclosing object. When XmNdropRectangles is NULL, the drop site is assumed to be the sensitive area of the enclosing widget. If XmNdropSiteType is XmDROP_SITE_COMPOSITE, this resource cannot be specified by the application.

    Retrieving this resource returns allocated memory that needs to be freed with the XtFree function.

XmNdropSiteActivity
    Indicates whether a drop site is active or inactive. The values are XmDROP_SITE_ACTIVE, XmDROP_SITE_INACTIVE, and XmDROP_SITE_IGNORE. An active drop site can receive a drop, whereas an inactive drop site is dormant. An inactive drop site is treated as if it was not a registered drop site and any drag-under visuals associated with entering or leaving the drop site do not occur. However, it is still used for clipping drag-under effects. A value of XmDROP_SITE_IGNORE indicates that a drop site should be ignored for all purposes.

XmNdropSiteOperations
    Specifies the set of valid operations associated with a drop site. 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, and XmDROP_MOVE. The value XmDROP_NOOP for this resource indicates that no operations are valid.

XmNdropSiteType
    Specifies the type of the drop site. The possible values are

    XmDROP_SITE_SIMPLE
        The widget does not have any additional children that are registered as drop sites.

    XmDROP_SITE_COMPOSITE
        The widget will have children that are registered as drop sites.

XmNimportTargets
    Specifies the list of target atoms that this drop site accepts.

XmNnumDropRectangles
    Specifies the number of rectangles in the XmNdropRectangles list. If the drop site type is XmDROP_SITE_COMPOSITE, this resource can not be specified by the application.

XmNnumImportTargets
    Specifies the number of atoms in the target atom list.

  Callback Information

A pointer to the following structure is passed to the XmNdragProc routine when the drop site receives crossing, motion, or operation changed messages:

typedef struct
{
        int reason;
        XEvent *event;
        Time timeStamp;
        Widget dragContext;
        Position x;
        Position y;
        unsigned char dropSiteStatus;
        unsigned char operation;
        unsigned char operations;
        Boolean animate;
} XmDragProcCallbackStruct, *XmDragProcCallback;

reason
    Indicates why the callback was invoked.

event
    Points to the XEvent that triggered the callback.

timeStamp
    Specifies the timestamp of the logical event.

dragContext
    Specifies the ID of the DragContext widget associated with the transaction.

x   Indicates the x-coordinate of the pointer relative to the drop site.

y   Indicates the y-coordinate of the pointer relative to the drop site.

dropSiteStatus
    An IN/OUT member that indicates whether or not a drop site is valid.

    When reason is XmCR_DROP_SITE_ENTER_MESSAGE or XmCR_OPERATION_CHANGED, or reason is XmCR_DRAG_MOTION or XmCR_DROP_SITE_LEAVE_MESSAGE and the pointer is not in the same drop site as on the previous invocation of the drag procedure, the toolkit 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.

    When the reason is XmCR_DRAG_MOTION or XmCR_DROP_SITE_LEAVE_MESSAGE and the pointer is within the same drop site as on the previous invocation of the drag procedure, the toolkit initializes dropSiteStatus to the value of dropSiteStatus at the time the previous invocation of the drag procedure returns.

    The drag procedure may change the value of this member. After the drag procedure returns, the toolkit uses the final value in initializing the dropSiteStatus member of the callback struct passed to the appropriate callbacks of the initiator.

operation
    An IN/OUT member that identifies an operation.

    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.

    The drag procedure may change the value of this member. After the drag procedure returns, the toolkit uses the final value in initializing the operation member of the callback struct passed to the appropriate callbacks of the initiator.

operations
    An IN/OUT member that indicates the set of operations supported for the source data.

    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 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.

    The drag procedure may change the value of this member. After the drag procedure returns, the toolkit uses the final value in initializing the operations member of the callback struct passed to the appropriate callbacks of the initiator.

animate
    An OUT member that indicates whether the toolkit or the receiver client provides drag-under effects for a valid drop site. If animate is set to True, the toolkit provides drop site animation per the XmNanimationStyle resource value; if it is set to False, the receiver generates drag-under animation effects.

A pointer to the following structure is passed to the XmNdropProc routine when the drop site receives a drop message:

typedef struct
{
        int reason;
        XEvent *event;
        Time timeStamp;
        Widget dragContext;
        Position x;
        Position y;
        unsigned char dropSiteStatus;
        unsigned char operation;
        unsigned char operations;
        unsigned char dropAction;
} XmDropProcCallbackStruct, *XmDropProcCallback;

reason
    Indicates why the callback was invoked.

event
    Specifies the XEvent that triggered the callback.

timeStamp
    Specifies the timestamp of the logical event.

dragContext
    Specifies the ID of the DragContext widget associated with the transaction.

x   Indicates the x-coordinate of the pointer relative to the drop site.

y   Indicates the y-coordinate of the pointer relative to the drop site.

dropSiteStatus
    An IN/OUT member that indicates whether or not a drop site is valid.

    The toolkit 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.

    The drop procedure may change the value of this member. After the drop procedure returns, the toolkit uses the final value in initializing the dropSiteStatus member of the XmDropStartCallbackStruct passed to the initiator's drop start callbacks (the DragContext's XmNdropStartCallback callbacks).

operation
    An IN/OUT member that identifies an operation.

    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 it finds none of these operations in the set, it initializes operation to XmDROP_NOOP.

    The drop procedure may change the value of this member. After the drop procedure returns, the toolkit uses the final value in initializing the operation member of the XmDropStartCallbackStruct passed to the initiator's drop start callbacks (the DragContext's XmNdropStartCallback callbacks).

operations
    An IN/OUT member that indicates the set of operations supported for the source data.

    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 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.

    The drop procedure may change the value of this member. After the drop procedure returns, the toolkit uses the final value in initializing the operations member of the XmDropStartCallbackStruct passed to the initiator's drop start callbacks (the DragContext's XmNdropStartCallback callbacks).

dropAction
    An IN/OUT member that identifies the action associated with the drop. The possible values are

    XmDROP
        A drop was attempted. If the drop site is valid, drop transfer handling proceeds.

    XmDROP_HELP
        The user has requested help on the drop site.

    The drop procedure may change the value of this member. After the drop procedure returns, the toolkit uses the final value in initializing the dropAction member of the XmDropStartCallbackStruct passed to the initiator's drop start callbacks (the DragContext's XmNdropStartCallback callbacks).

RELATED INFORMATION

XmDragContext(3), XmDragIcon(3), XmDropSiteConfigureStackingOrder(3), XmDropSiteEndUpdate(3), XmDropSiteQueryStackingOrder(3), XmDropSiteRegister(3), XmDropSiteStartUpdate(3), XmDropSiteUpdate(3), XmDropSiteUnregister(3), XmDropTransfer(3), and XmTargetsAreCompatible(3).