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[wxWidgets.git] / docs / latex / wx / dragimag.tex

\section{\class{wxDragImage}}\label{wxdragimage}

This class is used when you wish to drag an object on the screen,
and a simple cursor is not enough.

On Windows, the WIN32 API is used to do achieve smooth dragging. On other platforms,
wxGenericDragImage is used. Applications may also prefer to use
wxGenericDragImage on Windows, too.

To use this class, when you wish to start dragging an image, create a wxDragImage
object and store it somewhere you can access it as the drag progresses.
Call BeginDrag to start, and EndDrag to stop the drag. To move the image,
initially call Show and then Move. If you wish to update the screen contents
during the drag (for example, highlight an item as in the dragimag sample), first call Hide,
update the screen, call Move, and then call Show.

You can drag within one window, or you can use full-screen dragging
either across the whole screen, or just restricted to one area
of the screen to save resources. If you want the user to drag between
two windows, then you will need to use full-screen dragging.

Please see {\tt samples/dragimag} for an example.

\wxheading{Derived from}

\helpref{wxObject}{wxobject}

\wxheading{Include files}

<wx/dragimag.h>\\
<wx/generic/dragimgg.h>

\latexignore{\rtfignore{\wxheading{Members}}}

\membersection{wxDragImage::wxDragImage}\label{wxdragimageconstr}

\func{}{wxDragImage}{\void}

Default constructor.

\func{}{wxDragImage}{\param{const wxBitmap\& }{image}, \param{const wxCursor\& }{cursor = wxNullCursor},
 \param{const wxPoint& }{hotspot = wxPoint(0, 0)}}

Constructs a drag image from a bitmap and optional cursor.

\func{}{wxDragImage}{\param{const wxIcon\& }{image}, \param{const wxCursor\& }{cursor = wxNullCursor},
 \param{const wxPoint& }{hotspot = wxPoint(0, 0)}}

Constructs a drag image from an icon and optional cursor.

\func{}{wxDragImage}{\param{const wxString\& }{text}, \param{const wxCursor\& }{cursor = wxNullCursor},
 \param{const wxPoint& }{hotspot = wxPoint(0, 0)}}

Constructs a drag image from a text string and optional cursor.

\func{}{wxDragImage}{\param{const wxTreeCtrl\& }{treeCtrl}, \param{wxTreeItemId\& }{id}}

Constructs a drag image from the text in the given tree control item, and optional cursor.

\func{}{wxDragImage}{\param{const wxListCtrl\& }{treeCtrl}, \param{long }{id}}

Constructs a drag image from the text in the given tree control item, and optional cursor.

\wxheading{Parameters}

\docparam{image}{Icon or bitmap to be used as the drag image. The bitmap can
have a mask.}

\docparam{text}{Text used to construct a drag image.}

\docparam{cursor}{Optional cursor to combine with the image.}

\docparam{hotspot}{Position of the hotspot within the new image.}

\docparam{treeCtrl}{Tree control for constructing a tree drag image.}

\docparam{listCtrl}{List control for constructing a list drag image.}

\docparam{id}{Tree or list control item id.}

\membersection{wxDragImage::BeginDrag}\label{wxdragimagebegindrag}

\func{bool}{BeginDrag}{\param{const wxPoint\& }{hotspot}, \param{wxWindow* }{window}, \param{bool}{ fullScreen = FALSE}, \param{wxRect*}{ rect = NULL}}

Start dragging the image, in a window or full screen.

\func{bool}{BeginDrag}{\param{const wxPoint\& }{hotspot}, \param{wxWindow* }{window}, \param{wxWindow*}{ boundingWindow}}

Start dragging the image, using the first window to capture the mouse and the second
to specify the bounding area. This form is equivalent to using the first form,
but more convenient than working out the bounding rectangle explicitly.

You need to then call \helpref{wxDragImage::Show}{wxdragimageshow} 
and \helpref{wxDragImage::Move}{wxdragimagemove} to show the image on the screen.

Call \helpref{wxDragImage::EndDrag}{wxdragimageenddrag} when the drag has finished.

Note that this call automatically calls CaptureMouse.

\wxheading{Parameters}

\docparam{hotspot}{The location of the drag position relative to the upper-left corner
of the image.}

\docparam{window}{The window that captures the mouse, and within which the dragging
is limited unless {\it fullScreen} is TRUE.}

\docparam{boundingWindow}{In the second form of the function, specifies the
area within which the drag occurs.}

\docparam{fullScreen}{If TRUE, specifies that the drag will be visible over the full
screen, or over as much of the screen as is specified by {\it rect}. Note that the mouse will
still be captured in {\it window}.}

\docparam{rect}{If non-NULL, specifies the rectangle (in screen coordinates) that
bounds the dragging operation. Specifying this can make the operation more efficient
by cutting down on the area under consideration, and it can also make a visual difference
since the drag is clipped to this area.}

\membersection{wxDragImage::EndDrag}\label{wxdragimageenddrag}

\func{bool}{EndDrag}{\void}

Call this when the drag has finished.

Note that this call automatically calls ReleaseMouse.

\membersection{wxDragImage::Hide}\label{wxdragimagehide}

\func{bool}{Hide}{\void}

Hides the image. You may wish to call this before updating the window
contents (perhaps highlighting an item). Then call \helpref{wxDragImage::Move}{wxdragimagemove} 
and \helpref{wxDragImage::Show}{wxdragimageshow}.

\membersection{wxDragImage::Move}\label{wxdragimagemove}

\func{bool}{Move}{\param{const wxPoint\& }{pt}}

Call this to move the image to a new position. The image will only be shown if 
\helpref{wxDragImage::Show}{wxdragimageshow} has been called previously (for example
at the start of the drag).

{\it pt} is the position in window coordinates (or screen coordinates if no
window was specified to BeginDrag.

You can move the image either when the image is hidden or shown, but in general dragging
will be smoother if you move the image when it is shown.

\membersection{wxDragImage::Show}\label{wxdragimageshow}

\func{bool}{Show}{\void}

Shows the image. Call this at least once when dragging.