IDragDropSourceContentHelper Class Reference

#include <IDragDropSourceContentHelper.h>

Inheritance diagram for IDragDropSourceContentHelper:

Public Types
enum	{ kDefaultIID = IID_IDRAGDROPSOURCECONTENTHELPER }

Public Member Functions
virtual DragDrop::eHelperType	GetHelperType () const =0
virtual bool16	CouldStartDrag (IDragDropSource *, IEvent *e) const =0
virtual CursorSpec	GetDragCursor (IDragDropSource *, DragDrop::eTargetResponse, bool16 isDragLocal) const =0
virtual SysWireframe	CreateDragOutlineRegion (IDragDropSource *) const =0
virtual bool16	DoAddDragContent (IDragDropSource *, IDragDropController *)=0
virtual ErrorCode	ProcessDragDropCommand (IDragDropSource *, IDragDropController *, DragDrop::eCommandType)=0
Public Member Functions inherited from IPMUnknown
virtual IPMUnknown *	QueryInterface (PMIID interfaceID) const =0
virtual void	AddRef () const =0
virtual void	Release () const =0

Detailed Description

The IDragDropSourceContentHelper interface provides extensibility for drag drop sources. Drag source extensibility requires the source be derived from CDragDropSource_Extensible. Create a new boss with an IDragDropSourceContentHelper implementation combined with a IK2ServiceProvider implementation that corresponds to the service ID defined by the extensible drag source.

When the framework asks an extensible drag source if it is willing to start a drag, the source then asks each of it's content helpers if they could start a drag from the current mouse location. One helper is chosen based on willingness to begin a drag, and in the case of multiple helpers, prioritized by helper type. The extensible source then forwards the subsequent method calls that occur during the drag to the chosen helper.

See Also

IDragDropSource, IK2ServiceProvider, CDragDropSource_Extensible

Member Function Documentation

virtual bool16 IDragDropSourceContentHelper::CouldStartDrag ( IDragDropSource *  , IEvent *  e  ) const

pure virtual

Could this helper initiate a drag from the given mouse position?

Parameters

source	IN the drag drop source this helper is assisting
e	IN event containing current mouse position and modifiers

Returns

kTrue if a drag could be started.

virtual SysWireframe IDragDropSourceContentHelper::CreateDragOutlineRegion ( IDragDropSource *  ) const

pure virtual

Provide the outline region to be dragged with the cursor as feedback during the drag operation. Can return constants DragDrop::kNoDragOutline or DragDrop::kDefaultDragOutline when appropriate - caller is responsible for releasing the returned region, if any.

Parameters

source

IN the drag drop source this helper is assisting

Returns

SysWireframe to be used as drag feedback (caller is responsible for deleting this object)

virtual bool16 IDragDropSourceContentHelper::DoAddDragContent ( IDragDropSource *  , IDragDropController *    )

pure virtual

Add drag content for the current drag operation.

Parameters

source	IN the drag drop source this helper is assisting
controller	IN used to call IDragDropController::AddDragItem as necessary.

Returns

kTrue if the operation succeeded

virtual CursorSpec IDragDropSourceContentHelper::GetDragCursor ( IDragDropSource *  , DragDrop::eTargetResponse  , bool16  isDragLocal  ) const

pure virtual

Provide the cursor to be displayed during the drag based on the response from a target. Return DragDrop::kDefaultDragCursors to use the default platform cursors.

Parameters

source	IN the drag drop source this helper is assisting
targetResponse	IN what action the target intends to perform (nothing, copy, move, link)
isDragLocal	IN is the drag taking place within the source object (source and target are equivalent)

Returns

CursorSpec to display corresponding to target's intended action

virtual DragDrop::eHelperType IDragDropSourceContentHelper::GetHelperType ( ) const

pure virtual

Return the type or priority of the helper. This is used to resolve conflicts that can arise when more than one source content helper is capable of starting a drag drop operation. The presence of multiple helpers is not a conflict, a conflict would arise when one helper wants to replace or augment what another helper already does.

Returns

helper type appropriate for this helper. Use DragDrop::kDefaultHelper by default.

virtual ErrorCode IDragDropSourceContentHelper::ProcessDragDropCommand ( IDragDropSource *  , IDragDropController *  , DragDrop::eCommandType    )

pure virtual

Create and process (or schedule) the commands needed to complete the drop operation. Normally called on the drop target, this method is also called on sources when the original data needs to be deleted, as in a drag to the trash.

Parameters

source	IN the drag drop source this helper is assisting
controller	IN drag drop controller for this operation
commandType	IN which operation to perform (sources will only receive kDrag to delete data)

Returns

success or failure of the drop