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