interface/wx/dragimag.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        dragimag.h
   3 // Purpose:     interface of wxDragImage
   4 // Author:      wxWidgets team
   5 // Licence:     wxWindows licence
   6 /////////////////////////////////////////////////////////////////////////////
   7
   8 /**
   9     @class wxDragImage
  10
  11     This class is used when you wish to drag an object on the screen, and a
  12     simple cursor is not enough.
  13
  14     On Windows, the Win32 API is used to achieve smooth dragging. On other
  15     platforms, wxGenericDragImage is used. Applications may also prefer to use
  16     wxGenericDragImage on Windows, too.
  17
  18     To use this class, when you wish to start dragging an image, create a
  19     wxDragImage object and store it somewhere you can access it as the drag
  20     progresses. Call BeginDrag() to start, and EndDrag() to stop the drag. To
  21     move the image, initially call Show() and then Move(). If you wish to
  22     update the screen contents during the drag (for example, highlight an item
  23     as in the dragimag sample), first call Hide(), update the screen, call
  24     Move(), and then call Show().
  25
  26     You can drag within one window, or you can use full-screen dragging either
  27     across the whole screen, or just restricted to one area of the screen to
  28     save resources. If you want the user to drag between two windows, then you
  29     will need to use full-screen dragging.
  30
  31     If you wish to draw the image yourself, use wxGenericDragImage and override
  32     DoDrawImage() and GetImageRect().
  33
  34     @library{wxcore}
  35     @category{dnd}
  36
  37     @see @ref page_samples_dragimag
  38 */
  39 class wxDragImage : public wxObject
  40 {
  41 public:
  42     /**
  43         Default constructor.
  44     */
  45     wxDragImage();
  46     /**
  47         Constructs a drag image from a bitmap and optional cursor.
  48
  49         @param image
  50             Bitmap to be used as the drag image. The bitmap can have a mask.
  51         @param cursor
  52             Optional cursor to combine with the image.
  53     */
  54     wxDragImage(const wxBitmap& image, const wxCursor& cursor = wxNullCursor);
  55     /**
  56         Constructs a drag image from an icon and optional cursor.
  57
  58         @param image
  59             Icon to be used as the drag image.
  60         @param cursor
  61             Optional cursor to combine with the image.
  62     */
  63     wxDragImage(const wxIcon& image, const wxCursor& cursor = wxNullCursor);
  64     /**
  65         Constructs a drag image from a text string and optional cursor.
  66
  67         @param text
  68             Text used to construct a drag image.
  69         @param cursor
  70             Optional cursor to combine with the image.
  71     */
  72     wxDragImage(const wxString& text, const wxCursor& cursor = wxNullCursor);
  73     /**
  74         Constructs a drag image from the text in the given tree control item,
  75         and optional cursor.
  76
  77         @param treeCtrl
  78             Tree control for constructing a tree drag image.
  79         @param id
  80             Tree control item id.
  81     */
  82     wxDragImage(const wxTreeCtrl& treeCtrl, wxTreeItemId& id);
  83     /**
  84         Constructs a drag image from the text in the given list control item,
  85         and optional cursor.
  86
  87         @param listCtrl
  88             List control for constructing a list drag image.
  89         @param id
  90             List control item id.
  91     */
  92     wxDragImage(const wxListCtrl& listCtrl, long id);
  93     /**
  94         Start dragging the image, in a window or full screen.
  95
  96         You need to then call Show() and Move() to show the image on the
  97         screen. Call EndDrag() when the drag has finished.
  98
  99         Note that this call automatically calls CaptureMouse().
 100
 101         @param hotspot
 102             The location of the drag position relative to the upper-left corner
 103             of the image.
 104         @param window
 105             The window that captures the mouse, and within which the dragging
 106             is limited unless fullScreen is @true.
 107         @param fullScreen
 108             If @true, specifies that the drag will be visible over the full
 109             screen, or over as much of the screen as is specified by rect. Note
 110             that the mouse will still be captured in window.
 111         @param rect
 112             If non-@NULL, specifies the rectangle (in screen coordinates) that
 113             bounds the dragging operation. Specifying this can make the
 114             operation more efficient by cutting down on the area under
 115             consideration, and it can also make a visual difference since the
 116             drag is clipped to this area.
 117     */
 118     bool BeginDrag(const wxPoint& hotspot, wxWindow* window,
 119                    bool fullScreen = false, wxRect* rect = NULL);
 120     /**
 121         Start dragging the image, using the first window to capture the mouse
 122         and the second to specify the bounding area. This form is equivalent to
 123         using the first form, but more convenient than working out the bounding
 124         rectangle explicitly.
 125
 126         You need to then call Show() and Move() to show the image on the
 127         screen. Call EndDrag() when the drag has finished.
 128
 129         Note that this call automatically calls CaptureMouse().
 130
 131         @param hotspot
 132             The location of the drag position relative to the upper-left corner
 133             of the image.
 134         @param window
 135             The window that captures the mouse, and within which the dragging
 136             is limited.
 137         @param boundingWindow
 138             Specifies the area within which the drag occurs.
 139     */
 140     bool BeginDrag(const wxPoint& hotspot, wxWindow* window,
 141                    wxWindow* boundingWindow);
 142
 143     /**
 144         Draws the image on the device context with top-left corner at the given
 145         position.
 146
 147         This function is only available with wxGenericDragImage, to allow
 148         applications to draw their own image instead of using an actual bitmap.
 149         If you override this function, you must also override GetImageRect().
 150     */
 151     virtual bool DoDrawImage(wxDC& dc, const wxPoint& pos) const;
 152
 153     /**
 154         Call this when the drag has finished.
 155
 156         @note This function automatically releases mouse capture.
 157     */
 158     bool EndDrag();
 159
 160     /**
 161         Returns the rectangle enclosing the image, assuming that the image is
 162         drawn with its top-left corner at the given point.
 163
 164         This function is available in wxGenericDragImage only, and may be
 165         overridden (together with DoDrawImage()) to provide a virtual drawing
 166         capability.
 167     */
 168     virtual wxRect GetImageRect(const wxPoint& pos) const;
 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() and Show().
 173     */
 174     bool Hide();
 175
 176     /**
 177         Call this to move the image to a new position. The image will only be
 178         shown if Show() has been called previously (for example at the start of
 179         the drag).
 180
 181         @param pt
 182             The position in client coordinates (relative to the window
 183             specified in BeginDrag()).
 184
 185         You can move the image either when the image is hidden or shown, but in
 186         general dragging will be smoother if you move the image when it is
 187         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
 198         bitmap yourself. This can be desirable if you wish to avoid flicker by
 199         not having to redraw the updated window itself just before dragging,
 200         which can cause a flicker just as the drag starts. Instead, paint the
 201         drag image's backing bitmap to show the appropriate graphic @e minus
 202         the objects to be dragged, and leave the window itself to be updated by
 203         the drag image. This can provide eerily smooth, flicker-free drag
 204         behaviour.
 205
 206         The default implementation copies the window contents to the backing
 207         bitmap. A new implementation will normally copy information from
 208         another source, such as from its own backing bitmap if it has one, or
 209         directly from internal data structures.
 210
 211         This function is available in wxGenericDragImage only.
 212     */
 213     virtual bool UpdateBackingFromWindow(wxDC& windowDC, wxMemoryDC& destDC,
 214                                          const wxRect& sourceRect,
 215                                          const wxRect& destRect) const;
 216 };
 217