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	1	/////////////////////////////////////////////////////////////////////////////
	2	// Name: dnd.h
	3	// Purpose: topic overview
	4	// Author: wxWidgets team
	5	// RCS-ID: $Id$
	6	// Licence: wxWindows license
	7	/////////////////////////////////////////////////////////////////////////////
	8
	9	/*!
	10
	11	@page overview_dnd Drag and drop overview
	12
	13	Classes: #wxDataObject, #wxTextDataObject, #wxDropSource, #wxDropTarget,
	14	#wxTextDropTarget, #wxFileDropTarget
	15
	16	Note that @c wxUSE_DRAG_AND_DROP must be defined in @c setup.h in order
	17	to use drag and drop in wxWidgets.
	18
	19	See also: @ref overview_dataobject and @ref samplednd_overview.
	20
	21	It may be noted that data transfer to and from the clipboard is quite
	22	similar to data transfer with drag and drop and the code to implement
	23	these two types is almost the same. In particular, both data transfer
	24	mechanisms store data in some kind of #wxDataObject and identify its format(s)
	25	using the #wxDataFormat class.
	26
	27	To be a @e drag source, i.e. to provide the data which may be dragged by
	28	the user elsewhere, you should implement the following steps:
	29
	30	@li @b Preparation: First of all, a data object must be created and
	31	initialized with the data you wish to drag. For example:
	32
	33	@code
	34	wxTextDataObject my_data("This text will be dragged.");
	35	@endcode
	36
	37	@li <b>Drag start</b>: To start the dragging process (typically in response to a
	38	mouse click) you must call wxDropSource::DoDragDrop like this:
	39
	40	@code
	41	wxDropSource dragSource( this );
	42	dragSource.SetData( my_data );
	43	wxDragResult result = dragSource.DoDragDrop( true );
	44	@endcode
	45
	46	@li @b Dragging: The call to DoDragDrop() blocks the program until the user releases
	47	the mouse button (unless you override the #GiveFeedback function to do something
	48	special). When the mouse moves in a window of a program which understands the
	49	same drag-and-drop protocol (any program under Windows or any program supporting
	50	the XDnD protocol under X Windows), the corresponding #wxDropTarget methods
	51	are called - see below.
	52
	53	@li <b>Processing the result</b>: DoDragDrop() returns an @e effect code which
	54	is one of the values of @c wxDragResult enum (explained #here):
	55
	56	@code
	57	switch (result)
	58	{
	59	case wxDragCopy:
	60	// copy the data
	61	break;
	62	case wxDragMove:
	63	// move the data
	64	break;
	65	default:
	66	// do nothing
	67	break;
	68	}
	69	@endcode
	70
	71
	72	To be a @e drop target, i.e. to receive the data dropped by the user you should
	73	follow the instructions below:
	74
	75	@li @b Initialization: For a window to be a drop target, it needs to have
	76	an associated #wxDropTarget object. Normally, you will call wxWindow::SetDropTarget
	77	during window creation associating your drop target with it. You must derive a class from
	78	wxDropTarget and override its pure virtual methods. Alternatively, you may
	79	derive from #wxTextDropTarget or #wxFileDropTarget and override their OnDropText()
	80	or OnDropFiles() method.
	81
	82	@li @b Drop: When the user releases the mouse over a window, wxWidgets
	83	asks the associated wxDropTarget object if it accepts the data. For this,
	84	a #wxDataObject must be associated with the drop target and this data object will
	85	be responsible for the format negotiation between the drag source and the drop target.
	86	If all goes well, then #OnData will get called and the wxDataObject belonging to
	87	the drop target can get filled with data.
	88
	89	@li <b>The end</b>: After processing the data, DoDragDrop() returns either
	90	wxDragCopy or wxDragMove depending on the state of the keys Ctrl, Shift
	91	and Alt at the moment of the drop. There is currently no way for the drop
	92	target to change this return code.
	93
	94	*/
	95