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/////////////////////////////////////////////////////////////////////////////
// Name: dnd.h
// Purpose: topic overview
// Author: wxWidgets team
// Licence: wxWindows licence
/////////////////////////////////////////////////////////////////////////////
/**
@page overview_dnd Drag and Drop Overview
@tableofcontents
It may be noted that data transfer to and from the clipboard is quite
similar to data transfer with drag and drop and the code to implement
these two types is almost the same. In particular, both data transfer
mechanisms store data in some kind of wxDataObject and identify its format(s)
using the wxDataFormat class.
Note that @c wxUSE_DRAG_AND_DROP must be defined in @c setup.h in order
to use drag and drop in wxWidgets.
@see @ref overview_dataobject, @ref group_class_dnd, @ref page_samples_dnd
@section overview_dnd_dropsource Drop Source Requirements
To be a @e "drop source", i.e. to provide the data which may be dragged by
the user elsewhere, you should implement the following steps:
@li @b Preparation: First of all, a data object must be created and
initialized with the data you wish to drag. For example:
@code
wxTextDataObject my_data("This text will be dragged.");
@endcode
@li <b>Drag start</b>: To start the dragging process (typically in response to a
mouse click) you must call wxDropSource::DoDragDrop like this:
@code
wxDropSource dragSource( this );
dragSource.SetData( my_data );
wxDragResult result = dragSource.DoDragDrop( true );
@endcode
@li @b Dragging: The call to DoDragDrop() blocks the program until the user
releases the mouse button (unless you override the
wxDropSource::GiveFeedback function to do something special). When the
mouse moves in a window of a program which understands the same
drag-and-drop protocol (any program under Windows or any program supporting
the XDnD protocol under X Windows), the corresponding wxDropTarget methods
are called - see below.
@li <b>Processing the result</b>: DoDragDrop() returns an @e effect code which
is one of the values of @c wxDragResult enum (explained in wxDropTarget page):
@code
switch (result)
{
case wxDragCopy:
// copy the data
break;
case wxDragMove:
// move the data
break;
default:
// do nothing
break;
}
@endcode
@section overview_dnd_droptarget Drop Target Requirements
To be a @e "drop target", i.e. to receive the data dropped by the user you should
follow the instructions below:
@li @b Initialization: For a window to be a drop target, it needs to have
an associated wxDropTarget object. Normally, you will call wxWindow::SetDropTarget
during window creation associating your drop target with it. You must derive a class
from wxDropTarget and override its pure virtual methods. Alternatively, you may
derive from wxTextDropTarget or wxFileDropTarget and override their OnDropText()
or OnDropFiles() method.
@li @b Drop: When the user releases the mouse over a window, wxWidgets
asks the associated wxDropTarget object if it accepts the data. For this,
a wxDataObject must be associated with the drop target and this data object will
be responsible for the format negotiation between the drag source and the drop target.
If all goes well, then wxDropTarget::OnData will get called and the wxDataObject belonging
to the drop target can get filled with data.
@li <b>The end</b>: After processing the data, DoDragDrop() returns either
wxDragCopy or wxDragMove depending on the state of the keys Ctrl, Shift
and Alt at the moment of the drop. There is currently no way for the drop
target to change this return code.
*/
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