interface/dragimag.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        dragimag.h
   3 // Purpose:     documentation for wxDragImage class
   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
  54         Constructs a drag image an optional cursor. This constructor is only available
  55         for
  56         wxGenericDragImage, and can be used when the application
  57         supplies DoDrawImage() and GetImageRect().
  58
  59         @param image
  60         Icon or bitmap to be used as the drag image. The bitmap can
  61         have a mask.
  62
  63         @param text
  64         Text used to construct a drag image.
  65
  66         @param cursor
  67         Optional cursor to combine with the image.
  68
  69         @param hotspot
  70         This parameter is deprecated.
  71
  72         @param treeCtrl
  73         Tree control for constructing a tree drag image.
  74
  75         @param listCtrl
  76         List control for constructing a list drag image.
  77
  78         @param id
  79         Tree or list control item id.
  80     */
  81     wxDragImage();
  82     wxDragImage(const wxBitmap& image,
  83                 const wxCursor& cursor = wxNullCursor);
  84     wxDragImage(const wxIcon& image,
  85                 const wxCursor& cursor = wxNullCursor);
  86     wxDragImage(const wxString& text,
  87                 const wxCursor& cursor = wxNullCursor);
  88     wxDragImage(const wxTreeCtrl& treeCtrl, wxTreeItemId& id);
  89     wxDragImage(const wxListCtrl& treeCtrl, long id);
  90     wxDragImage(const wxCursor& cursor = wxNullCursor);
  91     //@}
  92
  93     //@{
  94     /**
  95         Start dragging the image, using the first window to capture the mouse and the
  96         second
  97         to specify the bounding area. This form is equivalent to using the first form,
  98         but more convenient than working out the bounding rectangle explicitly.
  99
 100         You need to then call Show()
 101         and Move() to show the image on the screen.
 102
 103         Call EndDrag() when the drag has finished.
 104
 105         Note that this call automatically calls CaptureMouse.
 106
 107         @param hotspot
 108         The location of the drag position relative to the upper-left corner
 109         of the image.
 110
 111         @param window
 112         The window that captures the mouse, and within which the dragging
 113         is limited unless fullScreen is @true.
 114
 115         @param boundingWindow
 116         In the second form of the function, specifies the
 117         area within which the drag occurs.
 118
 119         @param fullScreen
 120         If @true, specifies that the drag will be visible over the full
 121         screen, or over as much of the screen as is specified by rect. Note that the
 122         mouse will
 123         still be captured in window.
 124
 125         @param rect
 126         If non-@NULL, specifies the rectangle (in screen coordinates) that
 127         bounds the dragging operation. Specifying this can make the operation more
 128         efficient
 129         by cutting down on the area under consideration, and it can also make a visual
 130         difference
 131         since the drag is clipped to this area.
 132     */
 133     bool BeginDrag(const wxPoint& hotspot, wxWindow* window,
 134                    bool fullScreen = @false,
 135                    wxRect* rect = @NULL);
 136     bool BeginDrag(const wxPoint& hotspot, wxWindow* window,
 137                    wxWindow* boundingWindow);
 138     //@}
 139
 140     /**
 141         Draws the image on the device context with top-left corner at the given
 142         position.
 143
 144         This function is only available with wxGenericDragImage, to allow applications
 145         to
 146         draw their own image instead of using an actual bitmap. If you override this
 147         function,
 148         you must also override GetImageRect().
 149     */
 150     virtual bool DoDrawImage(wxDC& dc, const wxPoint& pos);
 151
 152     /**
 153         Call this when the drag has finished.
 154
 155         Note that this call automatically calls ReleaseMouse.
 156     */
 157     bool EndDrag();
 158
 159     /**
 160         Returns the rectangle enclosing the image, assuming that the image is drawn
 161         with its
 162         top-left corner at the given point.
 163
 164         This function is available in wxGenericDragImage only, and may be overridden
 165         (together with
 166         wxDragImage::DoDrawImage) to provide a virtual drawing capability.
 167     */
 168     virtual wxRect GetImageRect(const wxPoint& pos);
 169
 170     /**
 171         Hides the image. You may wish to call this before updating the window
 172         contents (perhaps highlighting an item). Then call Move()
 173         and Show().
 174     */
 175     bool Hide();
 176
 177     /**
 178         Call this to move the image to a new position. The image will only be shown if
 179         Show() has been called previously (for example
 180         at the start of the drag).
 181
 182         @e pt is the position in client coordinates (relative to the window specified
 183         in BeginDrag).
 184
 185         You can move the image either when the image is hidden or shown, but in general
 186         dragging
 187         will be smoother if you move the image when it is shown.
 188     */
 189     bool Move(const wxPoint& pt);
 190
 191     /**
 192         Shows the image. Call this at least once when dragging.
 193     */
 194     bool Show();
 195
 196     /**
 197         Override this if you wish to draw the window contents to the backing bitmap
 198         yourself. This can be desirable if you wish to avoid flicker by not having to
 199         redraw the updated window itself just before dragging, which can cause a
 200         flicker just
 201         as the drag starts. Instead, paint the drag image's backing bitmap to show the
 202         appropriate
 203         graphic @e minus the objects to be dragged, and leave the window itself to be
 204         updated
 205         by the drag image. This can provide eerily smooth, flicker-free drag behaviour.
 206
 207         The default implementation copies the window contents to the backing bitmap. A
 208         new
 209         implementation will normally copy information from another source, such as from
 210         its
 211         own backing bitmap if it has one, or directly from internal data structures.
 212
 213         This function is available in wxGenericDragImage only.
 214     */
 215     bool UpdateBackingFromWindow(wxDC& windowDC, wxMemoryDC& destDC,
 216                                  const wxRect& sourceRect,
 217                                  const wxRect& destRect);
 218 };