interface/dragimag.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        dragimag.h
   3 // Purpose:     interface of wxDragImage
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows license
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /**
  10     @class wxDragImage
  11     @wxheader{dragimag.h}
  12
  13     This class is used when you wish to drag an object on the screen,
  14     and a simple cursor is not enough.
  15
  16     On Windows, the Win32 API is used to achieve smooth dragging. On other
  17     platforms,
  18     wxGenericDragImage is used. Applications may also prefer to use
  19     wxGenericDragImage on Windows, too.
  20
  21     @b wxPython note: wxPython uses wxGenericDragImage on all platforms, but
  22     uses the wxDragImage name.
  23
  24     To use this class, when you wish to start dragging an image, create a
  25     wxDragImage
  26     object and store it somewhere you can access it as the drag progresses.
  27     Call BeginDrag to start, and EndDrag to stop the drag. To move the image,
  28     initially call Show and then Move. If you wish to update the screen contents
  29     during the drag (for example, highlight an item as in the dragimag sample),
  30     first call Hide,
  31     update the screen, call Move, and then call Show.
  32
  33     You can drag within one window, or you can use full-screen dragging
  34     either across the whole screen, or just restricted to one area
  35     of the screen to save resources. If you want the user to drag between
  36     two windows, then you will need to use full-screen dragging.
  37
  38     If you wish to draw the image yourself, use wxGenericDragImage and
  39     override wxDragImage::DoDrawImage and
  40     wxDragImage::GetImageRect.
  41
  42     Please see @c samples/dragimag for an example.
  43
  44     @library{wxcore}
  45     @category{FIXME}
  46 */
  47 class wxDragImage : public wxObject
  48 {
  49 public:
  50     //@{
  51     /**
  52         )
  53         Constructs a drag image an optional cursor. This constructor is only available
  54         for
  55         wxGenericDragImage, and can be used when the application
  56         supplies DoDrawImage() and GetImageRect().
  57
  58         @param image
  59             Icon or bitmap to be used as the drag image. The bitmap can
  60             have a mask.
  61         @param text
  62             Text used to construct a drag image.
  63         @param cursor
  64             Optional cursor to combine with the image.
  65         @param hotspot
  66             This parameter is deprecated.
  67         @param treeCtrl
  68             Tree control for constructing a tree drag image.
  69         @param listCtrl
  70             List control for constructing a list drag image.
  71         @param id
  72             Tree or list control item id.
  73     */
  74     wxDragImage();
  75     wxDragImage(const wxBitmap& image,
  76                 const wxCursor& cursor = wxNullCursor);
  77     wxDragImage(const wxIcon& image,
  78                 const wxCursor& cursor = wxNullCursor);
  79     wxDragImage(const wxString& text,
  80                 const wxCursor& cursor = wxNullCursor);
  81     wxDragImage(const wxTreeCtrl& treeCtrl, wxTreeItemId& id);
  82     wxDragImage(const wxListCtrl& treeCtrl, long id);
  83     wxDragImage(const wxCursor& cursor = wxNullCursor);
  84     //@}
  85
  86     //@{
  87     /**
  88         Start dragging the image, using the first window to capture the mouse and the
  89         second
  90         to specify the bounding area. This form is equivalent to using the first form,
  91         but more convenient than working out the bounding rectangle explicitly.
  92         You need to then call Show()
  93         and Move() to show the image on the screen.
  94         Call EndDrag() when the drag has finished.
  95         Note that this call automatically calls CaptureMouse.
  96
  97         @param hotspot
  98             The location of the drag position relative to the upper-left corner
  99             of the image.
 100         @param window
 101             The window that captures the mouse, and within which the dragging
 102             is limited unless fullScreen is @true.
 103         @param boundingWindow
 104             In the second form of the function, specifies the
 105             area within which the drag occurs.
 106         @param fullScreen
 107             If @true, specifies that the drag will be visible over the full
 108             screen, or over as much of the screen as is specified by rect. Note that
 109         the mouse will
 110             still be captured in window.
 111         @param rect
 112             If non-@NULL, specifies the rectangle (in screen coordinates) that
 113             bounds the dragging operation. Specifying this can make the operation more
 114         efficient
 115             by cutting down on the area under consideration, and it can also make a
 116         visual difference
 117             since the drag is clipped to this area.
 118     */
 119     bool BeginDrag(const wxPoint& hotspot, wxWindow* window,
 120                    bool fullScreen = false,
 121                    wxRect* rect = NULL);
 122     bool BeginDrag(const wxPoint& hotspot, wxWindow* window,
 123                    wxWindow* boundingWindow);
 124     //@}
 125
 126     /**
 127         Draws the image on the device context with top-left corner at the given
 128         position.
 129         This function is only available with wxGenericDragImage, to allow applications
 130         to
 131         draw their own image instead of using an actual bitmap. If you override this
 132         function,
 133         you must also override GetImageRect().
 134     */
 135     virtual bool DoDrawImage(wxDC& dc, const wxPoint& pos);
 136
 137     /**
 138         Call this when the drag has finished.
 139         Note that this call automatically calls ReleaseMouse.
 140     */
 141     bool EndDrag();
 142
 143     /**
 144         Returns the rectangle enclosing the image, assuming that the image is drawn
 145         with its
 146         top-left corner at the given point.
 147         This function is available in wxGenericDragImage only, and may be overridden
 148         (together with
 149         wxDragImage::DoDrawImage) to provide a virtual drawing capability.
 150     */
 151     virtual wxRect GetImageRect(const wxPoint& pos) const;
 152
 153     /**
 154         Hides the image. You may wish to call this before updating the window
 155         contents (perhaps highlighting an item). Then call Move()
 156         and Show().
 157     */
 158     bool Hide();
 159
 160     /**
 161         Call this to move the image to a new position. The image will only be shown if
 162         Show() has been called previously (for example
 163         at the start of the drag).
 164         @a pt is the position in client coordinates (relative to the window specified
 165         in BeginDrag).
 166         You can move the image either when the image is hidden or shown, but in general
 167         dragging
 168         will be smoother if you move the image when it is shown.
 169     */
 170     bool Move(const wxPoint& pt);
 171
 172     /**
 173         Shows the image. Call this at least once when dragging.
 174     */
 175     bool Show();
 176
 177     /**
 178         Override this if you wish to draw the window contents to the backing bitmap
 179         yourself. This can be desirable if you wish to avoid flicker by not having to
 180         redraw the updated window itself just before dragging, which can cause a
 181         flicker just
 182         as the drag starts. Instead, paint the drag image's backing bitmap to show the
 183         appropriate
 184         graphic @e minus the objects to be dragged, and leave the window itself to be
 185         updated
 186         by the drag image. This can provide eerily smooth, flicker-free drag behaviour.
 187         The default implementation copies the window contents to the backing bitmap. A
 188         new
 189         implementation will normally copy information from another source, such as from
 190         its
 191         own backing bitmap if it has one, or directly from internal data structures.
 192         This function is available in wxGenericDragImage only.
 193     */
 194     bool UpdateBackingFromWindow(wxDC& windowDC, wxMemoryDC& destDC,
 195                                  const wxRect& sourceRect,
 196                                  const wxRect& destRect) const;
 197 };
 198