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.
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).
XmDropSite resource set
Name
Class
Type
Default
Access
XmNanimationMask
XmCAnimationMask
Pixmap
XmUNSPECIFIED_PIXMAP
CSG
XmNanimationPixmap
XmCAnimationPixmap
Pixmap
XmUNSPECIFIED_PIXMAP
CSG
XmNanimationPixmapDepth
XmCAnimationPixmapDepth
int
0
CSG
XmNanimationStyle
XmCAnimationStyle
unsigned
char
XmDRAG_UNDER_HIGHLIGHT
CSG
XmNdragProc
XmCDragProc
XtCallbackProc
NULL
CSG
XmNdropProc
XmCDropProc
XtCallbackProc
NULL
CSG
XmNdropRectangles
XmCDropRectangles
XRectangle
dynamic
CSG
XmNdropSiteActivity
XmCDropSiteActivity
unsigned
char
XmDROP_SITE_ACTIVE
CSG
XmNdropSiteOperations
XmCDropSiteOperations
unsigned
char
XmDROP_MOVE
|
XmDROP_COPY
CSG
XmNdropSiteType
XmCDropSiteType
unsigned char
XmDROP_SITE_SIMPLE
CG
XmNimportTargets
XmCImportTargets
Atom
NULL
CSG
XmNnumDropRectangles
XmCNumDropRectangles
Cardinal
1
CSG
XmNnumImportTargets
XmCNumImportTargets
Cardinal
0
CSG
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_MESSAGE
XmCR_OPERATION_CHANGED_MESSAGE
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 struct 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.
XmNdropSiteActivity
Indicates whether a drop site is active or inactive. The values
are XmDROP_SITE_ACTIVE and XmDROP_SITE_INACTIVE. 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.
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 the reason is XmCR_DROP_SITE_ENTER_MESSAGE or
XmCR_OPERATION_CHANGED_MESSAGE, or when the reason is
XmCR_DRAG_MOTION_MESSAGE 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 as
follows:
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_MESSAGE 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).
