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