interface/wx/dcbuffer.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        dcbuffer.h
   3 // Purpose:     interface of wxBufferedDC
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows license
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /**
  10     @class wxBufferedDC
  11
  12     This class provides a simple way to avoid flicker: when drawing on it,
  13     everything is infact first drawn on an in-memory buffer (a wxBitmap) and
  14     then copied to the screen, using the associated wxDC, only once, when this
  15     object is destroyed. wxBufferedDC itself is typically associated with
  16     wxClientDC, if you want to use it in your @c EVT_PAINT handler, you should
  17     look at wxBufferedPaintDC instead.
  18
  19     When used like this, a valid @e DC must be specified in the constructor
  20     while the @e buffer bitmap doesn't have to be explicitly provided, by
  21     default this class will allocate the bitmap of required size itself.
  22     However using a dedicated bitmap can speed up the redrawing process by
  23     eliminating the repeated creation and destruction of a possibly big bitmap.
  24     Otherwise, wxBufferedDC can be used in the same way as any other device
  25     context.
  26
  27     There is another possible use for wxBufferedDC is to use it to maintain a
  28     backing store for the window contents. In this case, the associated @e DC
  29     may be @NULL but a valid backing store bitmap should be specified.
  30
  31     Finally, please note that GTK+ 2.0 as well as OS X provide double buffering
  32     themselves natively. You can either use wxWindow::IsDoubleBuffered() to
  33     determine whether you need to use buffering or not, or use
  34     wxAutoBufferedPaintDC to avoid needless double buffering on the systems
  35     which already do it automatically.
  36
  37     @library{wxcore}
  38     @category{dc}
  39
  40     @see wxDC, wxMemoryDC, wxBufferedPaintDC, wxAutoBufferedPaintDC
  41 */
  42 class wxBufferedDC : public wxMemoryDC
  43 {
  44 public:
  45     /**
  46         Default constructor. You must call one of the Init() methods later in
  47         order to use the device context.
  48     */
  49     wxBufferedDC();
  50
  51     /**
  52         Creates a buffer for the provided @a dc. Init() must not be called when
  53         using this constructor.
  54
  55         @param dc
  56             The underlying DC: everything drawn to this object will be flushed
  57             to this DC when this object is destroyed. You may pass @NULL in
  58             order to just initialize the buffer, and not flush it.
  59         @param area
  60             The size of the bitmap to be used for buffering (this bitmap is
  61             created internally when it is not given explicitly).
  62         @param style
  63             wxBUFFER_CLIENT_AREA to indicate that just the client area of the
  64             window is buffered, or wxBUFFER_VIRTUAL_AREA to indicate that the
  65             buffer bitmap covers the virtual area.
  66     */
  67     wxBufferedDC(wxDC* dc, const wxSize& area,
  68                  int style = wxBUFFER_CLIENT_AREA);
  69
  70     /**
  71         Creates a buffer for the provided dc. Init() must not be called when
  72         using this constructor.
  73
  74         @param dc
  75             The underlying DC: everything drawn to this object will be flushed
  76             to this DC when this object is destroyed. You may pass @NULL in
  77             order to just initialize the buffer, and not flush it.
  78         @param buffer
  79             Explicitly provided bitmap to be used for buffering: this is the
  80             most efficient solution as the bitmap doesn't have to be recreated
  81             each time but it also requires more memory as the bitmap is never
  82             freed. The bitmap should have appropriate size, anything drawn
  83             outside of its bounds is clipped.
  84         @param style
  85             wxBUFFER_CLIENT_AREA to indicate that just the client area of the
  86             window is buffered, or wxBUFFER_VIRTUAL_AREA to indicate that the
  87             buffer bitmap covers the virtual area.
  88     */
  89     wxBufferedDC(wxDC* dc, wxBitmap& buffer = wxNullBitmap,
  90                  int style = wxBUFFER_CLIENT_AREA);
  91
  92     /**
  93         Copies everything drawn on the DC so far to the underlying DC
  94         associated with this object, if any.
  95     */
  96     virtual ~wxBufferedDC();
  97
  98     //@{
  99     /**
 100         Initializes the object created using the default constructor. Please
 101         see the constructors for parameter details.
 102     */
 103     void Init(wxDC* dc, const wxSize& area,
 104               int style = wxBUFFER_CLIENT_AREA);
 105     void Init(wxDC* dc, wxBitmap& buffer = wxNullBitmap,
 106               int style = wxBUFFER_CLIENT_AREA);
 107     //@}
 108 };
 109
 110
 111
 112 /**
 113     @class wxAutoBufferedPaintDC
 114
 115     This wxDC derivative can be used inside of an @c EVT_PAINT() event handler
 116     to achieve double-buffered drawing. Just use this class instead of
 117     wxPaintDC and make sure wxWindow::SetBackgroundStyle() is called with
 118     wxBG_STYLE_CUSTOM somewhere in the class initialization code, and that's
 119     all you have to do to (mostly) avoid flicker.
 120
 121     The difference between wxBufferedPaintDC and this class is that this class
 122     won't double-buffer on platforms which have native double-buffering
 123     already, avoiding any unneccessary buffering to avoid flicker.
 124
 125     wxAutoBufferedPaintDC is simply a typedef of wxPaintDC on platforms that
 126     have native double-buffering, otherwise, it is a typedef of
 127     wxBufferedPaintDC.
 128
 129     @library{wxbase}
 130     @category{dc}
 131
 132     @see wxDC, wxBufferedPaintDC, wxPaintDC
 133 */
 134 class wxAutoBufferedPaintDC : public wxBufferedPaintDC
 135 {
 136 public:
 137     /**
 138         Constructor. Pass a pointer to the window on which you wish to paint.
 139     */
 140     wxAutoBufferedPaintDC(wxWindow* window);
 141 };
 142
 143
 144
 145 /**
 146     @class wxBufferedPaintDC
 147
 148     This is a subclass of wxBufferedDC which can be used inside of an
 149     @c EVT_PAINT() event handler to achieve double-buffered drawing. Just use
 150     this class instead of wxPaintDC and make sure
 151     wxWindow::SetBackgroundStyle() is called with wxBG_STYLE_CUSTOM somewhere
 152     in the class initialization code, and that's all you have to do to (mostly)
 153     avoid flicker. The only thing to watch out for is that if you are using
 154     this class together with wxScrolled, you probably do @b not want to call
 155     wxScrolled::PrepareDC() on it as it already does this internally for the
 156     real underlying wxPaintDC.
 157
 158     @library{wxcore}
 159     @category{dc}
 160
 161     @see wxDC, wxBufferedDC, wxAutoBufferedPaintDC, wxPaintDC
 162 */
 163 class wxBufferedPaintDC : public wxBufferedDC
 164 {
 165 public:
 166     //@{
 167     /**
 168         As with wxBufferedDC, you may either provide the bitmap to be used for
 169         buffering or let this object create one internally (in the latter case,
 170         the size of the client part of the window is used).
 171
 172         Pass wxBUFFER_CLIENT_AREA for the @a style parameter to indicate that
 173         just the client area of the window is buffered, or
 174         wxBUFFER_VIRTUAL_AREA to indicate that the buffer bitmap covers the
 175         virtual area.
 176     */
 177     wxBufferedPaintDC(wxWindow* window, wxBitmap& buffer,
 178                       int style = wxBUFFER_CLIENT_AREA);
 179     wxBufferedPaintDC(wxWindow* window,
 180                       int style = wxBUFFER_CLIENT_AREA);
 181     //@}
 182
 183     /**
 184         Copies everything drawn on the DC so far to the window associated with
 185         this object, using a wxPaintDC.
 186     */
 187     virtual ~wxBufferedPaintDC();
 188 };
 189