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, and a
  14     simple cursor is not enough.
  15
  16     On Windows, the Win32 API is used to achieve smooth dragging. On other
  17     platforms, wxGenericDragImage is used. Applications may also prefer to use
  18     wxGenericDragImage on Windows, too.
  19
  20     @beginWxPythonOnly
  21     wxPython uses wxGenericDragImage on all platforms, but uses the wxDragImage
  22     name.
  23     @endWxPythonOnly
  24
  25     To use this class, when you wish to start dragging an image, create a
  26     wxDragImage object and store it somewhere you can access it as the drag
  27     progresses. Call BeginDrag() to start, and EndDrag() to stop the drag. To
  28     move the image, initially call Show() and then Move(). If you wish to
  29     update the screen contents during the drag (for example, highlight an item
  30     as in the dragimag sample), first call Hide(), update the screen, call
  31     Move(), and then call Show().
  32
  33     You can drag within one window, or you can use full-screen dragging either
  34     across the whole screen, or just restricted to one area of the screen to
  35     save resources. If you want the user to drag between two windows, then you
  36     will need to use full-screen dragging.
  37
  38     If you wish to draw the image yourself, use wxGenericDragImage and override
  39     DoDrawImage() and GetImageRect().
  40
  41     @library{wxcore}
  42     @category{dnd}
  43
  44     @see @ref page_samples_dragimag
  45 */
  46 class wxDragImage : public wxObject
  47 {
  48 public:
  49     /**
  50         Default constructor.
  51     */
  52     wxDragImage();
  53     /**
  54         Constructs a drag image from a bitmap and optional cursor.
  55
  56         @param image
  57             Bitmap to be used as the drag image. The bitmap can have a mask.
  58         @param cursor
  59             Optional cursor to combine with the image.
  60         @param cursorHotspot
  61             This parameter is deprecated.
  62     */
  63     wxDragImage(const wxBitmap& image, const wxCursor& cursor = wxNullCursor,
  64                 const wxPoint& cursorHotspot = wxPoint(0, 0));
  65     /**
  66         Constructs a drag image from an icon and optional cursor.
  67
  68         @param image
  69             Icon to be used as the drag image.
  70         @param cursor
  71             Optional cursor to combine with the image.
  72         @param cursorHotspot
  73             This parameter is deprecated.
  74
  75         @beginWxPythonOnly
  76         This constructor is called wxDragIcon in wxPython.
  77         @endWxPythonOnly
  78     */
  79     wxDragImage(const wxIcon& image, const wxCursor& cursor = wxNullCursor,
  80                 const wxPoint& cursorHotspot = wxPoint(0, 0));
  81     /**
  82         Constructs a drag image from a text string and optional cursor.
  83
  84         @param text
  85             Text used to construct a drag image.
  86         @param cursor
  87             Optional cursor to combine with the image.
  88         @param cursorHotspot
  89             This parameter is deprecated.
  90
  91         @beginWxPythonOnly
  92         This constructor is called wxDragString in wxPython.
  93         @endWxPythonOnly
  94     */
  95     wxDragImage(const wxString& text, const wxCursor& cursor = wxNullCursor,
  96                 const wxPoint& cursorHotspot = wxPoint(0, 0));
  97     /**
  98         Constructs a drag image from the text in the given tree control item,
  99         and optional cursor.
 100
 101         @param treeCtrl
 102             Tree control for constructing a tree drag image.
 103         @param id
 104             Tree control item id.
 105
 106         @beginWxPythonOnly
 107         This constructor is called wxDragTreeItem in wxPython.
 108         @endWxPythonOnly
 109     */
 110     wxDragImage(const wxTreeCtrl& treeCtrl, wxTreeItemId& id);
 111     /**
 112         Constructs a drag image from the text in the given list control item,
 113         and optional cursor.
 114
 115         @param listCtrl
 116             List control for constructing a list drag image.
 117         @param id
 118             List control item id.
 119
 120         @beginWxPythonOnly
 121         This constructor is called wxDragListItem in wxPython.
 122         @endWxPythonOnly
 123     */
 124     wxDragImage(const wxListCtrl& listCtrl, long id);
 125     /**
 126         Constructs a drag image an optional cursor. This constructor is only
 127         available for wxGenericDragImage, and can be used when the application
 128         supplies DoDrawImage() and GetImageRect().
 129
 130         @param cursor
 131             Optional cursor to combine with the image.
 132         @param cursorHotspot
 133             This parameter is deprecated.
 134     */
 135     wxDragImage(const wxCursor& cursor = wxNullCursor,
 136                 const wxPoint& cursorHotspot = wxPoint(0, 0));
 137
 138     /**
 139         Start dragging the image, in a window or full screen.
 140
 141         You need to then call Show() and Move() to show the image on the
 142         screen. Call EndDrag() when the drag has finished.
 143
 144         Note that this call automatically calls CaptureMouse().
 145
 146         @param hotspot
 147             The location of the drag position relative to the upper-left corner
 148             of the image.
 149         @param window
 150             The window that captures the mouse, and within which the dragging
 151             is limited unless fullScreen is @true.
 152         @param fullScreen
 153             If @true, specifies that the drag will be visible over the full
 154             screen, or over as much of the screen as is specified by rect. Note
 155             that the mouse will still be captured in window.
 156         @param rect
 157             If non-@NULL, specifies the rectangle (in screen coordinates) that
 158             bounds the dragging operation. Specifying this can make the
 159             operation more efficient by cutting down on the area under
 160             consideration, and it can also make a visual difference since the
 161             drag is clipped to this area.
 162     */
 163     bool BeginDrag(const wxPoint& hotspot, wxWindow* window,
 164                    bool fullScreen = false, wxRect* rect = NULL);
 165     /**
 166         Start dragging the image, using the first window to capture the mouse
 167         and the second to specify the bounding area. This form is equivalent to
 168         using the first form, but more convenient than working out the bounding
 169         rectangle explicitly.
 170
 171         You need to then call Show() and Move() to show the image on the
 172         screen. Call EndDrag() when the drag has finished.
 173
 174         Note that this call automatically calls CaptureMouse().
 175
 176         @param hotspot
 177             The location of the drag position relative to the upper-left corner
 178             of the image.
 179         @param window
 180             The window that captures the mouse, and within which the dragging
 181             is limited.
 182         @param boundingWindow
 183             Specifies the area within which the drag occurs.
 184     */
 185     bool BeginDrag(const wxPoint& hotspot, wxWindow* window,
 186                    wxWindow* boundingWindow);
 187
 188     /**
 189         Draws the image on the device context with top-left corner at the given
 190         position.
 191
 192         This function is only available with wxGenericDragImage, to allow
 193         applications to draw their own image instead of using an actual bitmap.
 194         If you override this function, you must also override GetImageRect().
 195     */
 196     virtual bool DoDrawImage(wxDC& dc, const wxPoint& pos);
 197
 198     /**
 199         Call this when the drag has finished.
 200
 201         @note This function automatically releases mouse capture.
 202     */
 203     bool EndDrag();
 204
 205     /**
 206         Returns the rectangle enclosing the image, assuming that the image is
 207         drawn with its top-left corner at the given point.
 208
 209         This function is available in wxGenericDragImage only, and may be
 210         overridden (together with DoDrawImage()) to provide a virtual drawing
 211         capability.
 212     */
 213     virtual wxRect GetImageRect(const wxPoint& pos) const;
 214
 215     /**
 216         Hides the image. You may wish to call this before updating the window
 217         contents (perhaps highlighting an item). Then call Move() and Show().
 218     */
 219     bool Hide();
 220
 221     /**
 222         Call this to move the image to a new position. The image will only be
 223         shown if Show() has been called previously (for example at the start of
 224         the drag).
 225
 226         @param pt
 227             The position in client coordinates (relative to the window
 228             specified in BeginDrag()).
 229
 230         You can move the image either when the image is hidden or shown, but in
 231         general dragging will be smoother if you move the image when it is
 232         shown.
 233     */
 234     bool Move(const wxPoint& pt);
 235
 236     /**
 237         Shows the image. Call this at least once when dragging.
 238     */
 239     bool Show();
 240
 241     /**
 242         Override this if you wish to draw the window contents to the backing
 243         bitmap yourself. This can be desirable if you wish to avoid flicker by
 244         not having to redraw the updated window itself just before dragging,
 245         which can cause a flicker just as the drag starts. Instead, paint the
 246         drag image's backing bitmap to show the appropriate graphic @e minus
 247         the objects to be dragged, and leave the window itself to be updated by
 248         the drag image. This can provide eerily smooth, flicker-free drag
 249         behaviour.
 250
 251         The default implementation copies the window contents to the backing
 252         bitmap. A new implementation will normally copy information from
 253         another source, such as from its own backing bitmap if it has one, or
 254         directly from internal data structures.
 255
 256         This function is available in wxGenericDragImage only.
 257     */
 258     bool UpdateBackingFromWindow(wxDC& windowDC, wxMemoryDC& destDC,
 259                                  const wxRect& sourceRect,
 260                                  const wxRect& destRect) const;
 261 };
 262