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 licence
   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     */
  60     wxDragImage(const wxBitmap& image, const wxCursor& cursor = wxNullCursor);
  61     /**
  62         Constructs a drag image from an icon and optional cursor.
  63
  64         @param image
  65             Icon to be used as the drag image.
  66         @param cursor
  67             Optional cursor to combine with the image.
  68
  69         @beginWxPythonOnly
  70         This constructor is called wxDragIcon in wxPython.
  71         @endWxPythonOnly
  72     */
  73     wxDragImage(const wxIcon& image, const wxCursor& cursor = wxNullCursor);
  74     /**
  75         Constructs a drag image from a text string and optional cursor.
  76
  77         @param text
  78             Text used to construct a drag image.
  79         @param cursor
  80             Optional cursor to combine with the image.
  81
  82         @beginWxPythonOnly
  83         This constructor is called wxDragString in wxPython.
  84         @endWxPythonOnly
  85     */
  86     wxDragImage(const wxString& text, const wxCursor& cursor = wxNullCursor);
  87     /**
  88         Constructs a drag image from the text in the given tree control item,
  89         and optional cursor.
  90
  91         @param treeCtrl
  92             Tree control for constructing a tree drag image.
  93         @param id
  94             Tree control item id.
  95
  96         @beginWxPythonOnly
  97         This constructor is called wxDragTreeItem in wxPython.
  98         @endWxPythonOnly
  99     */
 100     wxDragImage(const wxTreeCtrl& treeCtrl, wxTreeItemId& id);
 101     /**
 102         Constructs a drag image from the text in the given list control item,
 103         and optional cursor.
 104
 105         @param listCtrl
 106             List control for constructing a list drag image.
 107         @param id
 108             List control item id.
 109
 110         @beginWxPythonOnly
 111         This constructor is called wxDragListItem in wxPython.
 112         @endWxPythonOnly
 113     */
 114     wxDragImage(const wxListCtrl& listCtrl, long id);
 115     /**
 116         Start dragging the image, in a window or full screen.
 117
 118         You need to then call Show() and Move() to show the image on the
 119         screen. Call EndDrag() when the drag has finished.
 120
 121         Note that this call automatically calls CaptureMouse().
 122
 123         @param hotspot
 124             The location of the drag position relative to the upper-left corner
 125             of the image.
 126         @param window
 127             The window that captures the mouse, and within which the dragging
 128             is limited unless fullScreen is @true.
 129         @param fullScreen
 130             If @true, specifies that the drag will be visible over the full
 131             screen, or over as much of the screen as is specified by rect. Note
 132             that the mouse will still be captured in window.
 133         @param rect
 134             If non-@NULL, specifies the rectangle (in screen coordinates) that
 135             bounds the dragging operation. Specifying this can make the
 136             operation more efficient by cutting down on the area under
 137             consideration, and it can also make a visual difference since the
 138             drag is clipped to this area.
 139     */
 140     bool BeginDrag(const wxPoint& hotspot, wxWindow* window,
 141                    bool fullScreen = false, wxRect* rect = NULL);
 142     /**
 143         Start dragging the image, using the first window to capture the mouse
 144         and the second to specify the bounding area. This form is equivalent to
 145         using the first form, but more convenient than working out the bounding
 146         rectangle explicitly.
 147
 148         You need to then call Show() and Move() to show the image on the
 149         screen. Call EndDrag() when the drag has finished.
 150
 151         Note that this call automatically calls CaptureMouse().
 152
 153         @param hotspot
 154             The location of the drag position relative to the upper-left corner
 155             of the image.
 156         @param window
 157             The window that captures the mouse, and within which the dragging
 158             is limited.
 159         @param boundingWindow
 160             Specifies the area within which the drag occurs.
 161     */
 162     bool BeginDrag(const wxPoint& hotspot, wxWindow* window,
 163                    wxWindow* boundingWindow);
 164
 165     /**
 166         Draws the image on the device context with top-left corner at the given
 167         position.
 168
 169         This function is only available with wxGenericDragImage, to allow
 170         applications to draw their own image instead of using an actual bitmap.
 171         If you override this function, you must also override GetImageRect().
 172     */
 173     virtual bool DoDrawImage(wxDC& dc, const wxPoint& pos) const;
 174
 175     /**
 176         Call this when the drag has finished.
 177
 178         @note This function automatically releases mouse capture.
 179     */
 180     bool EndDrag();
 181
 182     /**
 183         Returns the rectangle enclosing the image, assuming that the image is
 184         drawn with its top-left corner at the given point.
 185
 186         This function is available in wxGenericDragImage only, and may be
 187         overridden (together with DoDrawImage()) to provide a virtual drawing
 188         capability.
 189     */
 190     virtual wxRect GetImageRect(const wxPoint& pos) const;
 191
 192     /**
 193         Hides the image. You may wish to call this before updating the window
 194         contents (perhaps highlighting an item). Then call Move() and Show().
 195     */
 196     bool Hide();
 197
 198     /**
 199         Call this to move the image to a new position. The image will only be
 200         shown if Show() has been called previously (for example at the start of
 201         the drag).
 202
 203         @param pt
 204             The position in client coordinates (relative to the window
 205             specified in BeginDrag()).
 206
 207         You can move the image either when the image is hidden or shown, but in
 208         general dragging will be smoother if you move the image when it is
 209         shown.
 210     */
 211     bool Move(const wxPoint& pt);
 212
 213     /**
 214         Shows the image. Call this at least once when dragging.
 215     */
 216     bool Show();
 217
 218     /**
 219         Override this if you wish to draw the window contents to the backing
 220         bitmap yourself. This can be desirable if you wish to avoid flicker by
 221         not having to redraw the updated window itself just before dragging,
 222         which can cause a flicker just as the drag starts. Instead, paint the
 223         drag image's backing bitmap to show the appropriate graphic @e minus
 224         the objects to be dragged, and leave the window itself to be updated by
 225         the drag image. This can provide eerily smooth, flicker-free drag
 226         behaviour.
 227
 228         The default implementation copies the window contents to the backing
 229         bitmap. A new implementation will normally copy information from
 230         another source, such as from its own backing bitmap if it has one, or
 231         directly from internal data structures.
 232
 233         This function is available in wxGenericDragImage only.
 234     */
 235     virtual bool UpdateBackingFromWindow(wxDC& windowDC, wxMemoryDC& destDC,
 236                                          const wxRect& sourceRect,
 237                                          const wxRect& destRect) const;
 238 };
 239