\section{Drag-and-drop and clipboard overview}\label{wxdndoverview}
-Classes: \helpref{wxDataObject}{wxdataobject}
+Classes: \helpref{wxDataObject}{wxdataobject},
+\helpref{wxTextDataObject}{wxtextdataobject},
+\helpref{wxDropSource}{wxdropsource},
+\helpref{wxDropTarget}{wxdroptarget},
+\helpref{wxTextDropTarget}{wxtextdroptarget},
+\helpref{wxFileDropTarget}{wxfiledroptarget}
-% \helpref{wxTextDataObject}{wxtextdataobject}
-% \helpref{wxDropSource}{wxdropsource}
-% \helpref{wxDropTarget}{wxdroptarget}
-% \helpref{wxTextDropTarget}{wxtextdroptarget}
-% \helpref{wxFileDropTarget}{wxfiledroptarget}
-
-Samples: see the dnd sample.
-
-Headers: <wx/dataobj.h>, <wx/dropsrc.h and <wx/droptgt.h>>
-(note that wxUSE\_DRAG\_AND\_DROP must be defined in setup.h)
+Note that wxUSE\_DRAG\_AND\_DROP must be defined in setup.h in order
+to use Drag'n'Drop in wxWindows.
This overview describes wxWindows support for drag and drop and clipboard
operations. Both of these topics are discussed here because, in fact, they're
-quite related. Drag and drop and clipboard are just too ways of passing the
+quite related. Drag and drop and clipboard are just two ways of passing the
data around and so the code required to implement both types of the operations
is almost the same.
-Both operations involve passing some data from one program to another
-(although the data may be received in the same program as well). In the case
-of clipboard transfer, the data is first places on the clipboard and then
-pasted into the destination program while for a drag-and-drop operation the
+Both operations involve passing some data from one program to another,
+although the data can be received in the same program as the source. In the case
+of clipboard transfer, the data is first placed on the clipboard and then
+pasted into the destination program, while for a drag-and-drop operation the
data object is not stored anywhere but is created when the user starts
-dragging and is destroyed as soon as he ends it (whether the operation was
-ended successfully or cancelled).
+dragging and is destroyed as soon as he ends it, whether the operation was
+ended successfully or cancelled.
To be a {\it drag source}, i.e. to provide the data which may be dragged by
-user elsewhere you should implement the following steps:
+user elsewhere, you should implement the following steps:
\begin{itemize}\itemsep=0pt
\item {\bf Preparation:} First of all, the data object must be created and
-initilized with the data you wish to drag. For example:
+initialized with the data you wish to drag. For example:
\begin{verbatim}
- wxTextDataObject data("This string will be dragged.");
+ wxDataObject *my_data = new wxTextDataObject data("This string will be dragged.");
\end{verbatim}
-
-Of course, the data object may contain arbitrary data of any type, but for
-this you should derive your own class from
-\helpref{wxDataObject}{wxdataobject} overriding all of its pure virtual
-functions.
-
\item{\bf Drag start:} To start dragging process (typically in response to a
-mouse click) you must call \helpref{DoDragDrop}{wxdropsourcedodragdrop}
-function of wxDropSource object which should be constructed like this:
+mouse click) you must call \helpref{DoDragDrop}{wxdropsourcedodragdrop} function
+of wxDropSource object which should be constructed like this:
\begin{verbatim}
- wxDropSource dragSource(data, this);
-
- // or also:
-
- wxDropSource dragSource(this);
- dragSource.SetData(data);
+ wxDropSource dragSource( this );
+ dragSource.SetData( my_data );
\end{verbatim}
-
\item {\bf Dragging:} The call to DoDragDrop() blocks until the user release the
mouse button (unless you override \helpref{GiveFeedback}{wxdropsourcegivefeedback} 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 XDnD protocol
-under X Windows), the corresponding \helpref{wxDropTarget}{wxdroptarget} methods
+same drag-and-drop protocol (any program under Windows or any program supporting the
+XDnD protocol under X Windows), the corresponding \helpref{wxDropTarget}{wxdroptarget} methods
are called - see below.
-
-\item {\bf Processing the result:} DoDragDrop() returns an {\it effect code}
-which is one of the values of \helpref{wxDragResult}{wxdragresult} enum. Codes
+\item {\bf Processing the result:} DoDragDrop() returns an {\it effect code} which
+is one of the values of \helpref{wxDragResult}{wxdropsource} enum. Codes
of wxDragError, wxDragNone and wxDragCancel have the obvious meaning and mean
that there is nothing to do on the sending end (except of possibly logging the
error in the first case). wxDragCopy means that the data has been successfully
special because it means that the data must be deleted from where it was
copied. If it doesn't make sense (dragging selected text from a read-only
file) you should pass FALSE as parameter to DoDragDrop() in the previous step.
-
\end{itemize}
-
To be a {\it drop target}, i.e. to receive the data dropped by user you should
follow the instructions below:
\begin{itemize}\itemsep=0pt
\item {\bf Initialization:} For a window to be drop target, it needs to have
an associated \helpref{wxDropTarget}{wxdroptarget} object. Normally, you will
-call wxWindow::\helpref{SetDropTarget}{wxwindowsetdroptarget} during window
+call \helpref{wxWindow::SetDropTarget}{wxwindowsetdroptarget} during window
creation associating you drop target with it. You must derive a class from
wxDropTarget and override its pure virtual methods. Alternatively, you may
derive from \helpref{wxTextDropTarget}{wxtextdroptarget} or
\helpref{wxFileDropTarget}{wxfiledroptarget} and override their OnDropText()
or OnDropFiles() method.
-
\item {\bf Drop:} When the user releases the mouse over a window, wxWindows
-queries the associated wxDropTarget object if it accepts the data. For
-this, \helpref{GetFormatCount}{wxdroptargetgetformatcount} and
-\helpref{GetFormat}{wxdroptargetgetformat} are used and if the format is
-supported (i.e. is one of returned by GetFormat()),
-then \helpref{OnDrop}{wxdroptargetondrop} is called.
-Otherwise, \helpref{wxDragNone}{stdformat} is returned by DoDragDrop() and
-nothing happens.
-
+queries the associated wxDropTarget object if it accepts the data. For this,
+a \helpref{wxDataObject}{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 \helpref{OnData}{wxdroptargetondata}
+will get called and the wxDataObject belonging to the drop target can get
+filled with data.
\item {\bf The end:} 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 drop. There is currently no way for the drop
target to change this return code.
-
\end{itemize}
projects / wxWidgets.git / blobdiff