DoDragDrop
Carries out
an OLE drag and drop operation.
WINOLEAPI DoDragDrop(
IDataObject * pDataObject, |
//Pointer to the data object |
IDropSource * pDropSource, |
//Pointer to the source |
DWORD dwOKEffect, |
//Effects allowed by the source |
DWORD * pdwEffect |
//Pointer to effects on the source |
); |
|
Parameters
pDataObject
[in] Pointer
to the IDataObject
pDropSource
[in] Pointer
to an implementation of the IDropSource
dwOKEffect
[in] Effects
the source allows in the OLE drag-and-drop operation. Most significant is
whether it permits a move. The dwOKEffect and pdwEffect
parameters obtain values from the DROPEFFECTVK63LO enumeration. For a list of values, see DROPEFFECT.
pdwEffect
[out] Pointer
to a value that indicates how the OLE drag-and-drop operation affected the
source data. The pdwEffect parameter is set only if the operation is not
canceled.
Return Values
This function
supports the standard return value E_OUTOFMEMORY, as well as the following:
DRAGDROP_S_DROP
The OLE
drag-and-drop operation was successful.
DRAGDROP_S_CANCEL
The OLE drag-and-drop
operation was canceled.
E_UNSPEC
Unexpected
error occurred.
Remarks
If you are
developing an application that can act as a data source for an OLE
drag-and-drop operation, you must call DoDragDrop when you detect that
the user has started an OLE drag-and-drop operation.
The DoDragDrop
function enters a loop in which it calls various methods in the IDropSource
1. The DoDragDrop function determines the
window under the current cursor location. It then checks to see if this window
is a valid drop target.
2. If the window is a valid drop target, DoDragDrop
calls IDropTarget::DragEnter .
This method supplies an effect code indicating what would happen if the drop
actually occurred. For a list of valid drop effects, see the DROPEFFECT enumeration.
3. DoDragDrop calls IDropSource::GiveFeedback with the effect code so
that the drop source interface can provide appropriate visual feedback to the
user. The pDropSource pointer passed into DoDragDrop specifies
the appropriate IDropSource interface.
4. DoDragDrop tracks mouse cursor
movements and changes in the keyboard or mouse button state.
If the user moves out of a window, DoDragDrop
calls IDropTarget::DragLeave .
If the mouse enters another window, DoDragDrop
determines if that window is a valid drop target and then calls IDropTarget::DragEnter for that window.
If the mouse moves but stays within the same
window, DoDragDrop calls IDropTarget::DragOver .
5. If there is a change in the keyboard or mouse
button state, DoDragDrop calls IDropSource::QueryContinueDrag and determines whether to
continue the drag, to drop the data, or to cancel the operation based on the
return value.
If the return value is S_OK, DoDragDrop
first calls IDropTarget::DragOver to continue the operation. This method
returns a new effect value and DoDragDrop then calls IDropSource::GiveFeedback with the new effect so
appropriate visual feedback can be set. For a list of valid drop effects, see
the DROPEFFECT
enumeration. IDropTarget::DragOver and IDropSource::GiveFeedback
are paired so that as the mouse moves across the drop target, the user is given
the most up-to-date feedback on the mouse s
position.
If the return value is DRAGDROP_S_DROP, DoDragDrop
calls IDropTarget::Drop .
The DoDragDrop function returns the last effect code to the source, so
the source application can perform the appropriate operation on the source
data, for example, cut the data if the operation was a move.
If the return value is DRAGDROP_S_CANCEL, the
DoDragDrop function calls IDropTarget::DragLeave .
See Also