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 in fact 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     /**
  53         Creates a buffer for the provided @dc. Init() must not be called when
  54         using this constructor.
  55
  56         @param dc
  57             The underlying DC: everything drawn to this object will be flushed
  58             to this DC when this object is destroyed. You may pass @NULL in
  59             order to just initialize the buffer, and not flush it.
  60         @param area
  61             The size of the bitmap to be used for buffering (this bitmap is
  62             created internally when it is not given explicitly).
  63         @param buffer
  64             Explicitly provided bitmap to be used for buffering: this is the
  65             most efficient solution as the bitmap doesn't have to be recreated
  66             each time but it also requires more memory as the bitmap is never
  67             freed. The bitmap should have appropriate size, anything drawn
  68             outside of its bounds is clipped.
  69         @param style
  70             wxBUFFER_CLIENT_AREA to indicate that just the client area of the
  71             window is buffered, or wxBUFFER_VIRTUAL_AREA to indicate that the
  72             buffer bitmap covers the virtual area.
  73     */
  74     wxBufferedDC(wxDC* dc, const wxSize& area,
  75                  int style = wxBUFFER_CLIENT_AREA);
  76     wxBufferedDC(wxDC* dc, wxBitmap& buffer,
  77                  int style = wxBUFFER_CLIENT_AREA);
  78     //@}
  79
  80     /**
  81         Copies everything drawn on the DC so far to the underlying DC
  82         associated with this object, if any.
  83     */
  84     ~wxBufferedDC();
  85
  86     //@{
  87     /**
  88         Initializes the object created using the default constructor. Please
  89         see the constructors for parameter details.
  90     */
  91     void Init(wxDC* dc, const wxSize& area,
  92               int style = wxBUFFER_CLIENT_AREA);
  93     void Init(wxDC* dc, wxBitmap& buffer,
  94               int style = wxBUFFER_CLIENT_AREA);
  95     //@}
  96 };
  97
  98
  99
 100 /**
 101     @class wxAutoBufferedPaintDC
 102
 103     This wxDC derivative can be used inside of an @c EVT_PAINT() event handler
 104     to achieve double-buffered drawing. Just use this class instead of
 105     wxPaintDC and make sure wxWindow::SetBackgroundStyle() is called with
 106     wxBG_STYLE_CUSTOM somewhere in the class initialization code, and that's
 107     all you have to do to (mostly) avoid flicker.
 108
 109     The difference between wxBufferedPaintDC and this class is that this class
 110     won't double-buffer on platforms which have native double-buffering
 111     already, avoiding any unneccessary buffering to avoid flicker.
 112
 113     wxAutoBufferedPaintDC is simply a typedef of wxPaintDC on platforms that
 114     have native double-buffering, otherwise, it is a typedef of
 115     wxBufferedPaintDC.
 116
 117     @library{wxbase}
 118     @category{dc}
 119
 120     @see wxDC, wxBufferedPaintDC, wxPaintDC
 121 */
 122 class wxAutoBufferedPaintDC : public wxBufferedPaintDC
 123 {
 124 public:
 125     /**
 126         Constructor. Pass a pointer to the window on which you wish to paint.
 127     */
 128     wxAutoBufferedPaintDC(wxWindow* window);
 129 };
 130
 131
 132
 133 /**
 134     @class wxBufferedPaintDC
 135
 136     This is a subclass of wxBufferedDC which can be used inside of an
 137     @c EVT_PAINT() event handler to achieve double-buffered drawing. Just use
 138     this class instead of wxPaintDC and make sure
 139     wxWindow::SetBackgroundStyle() is called with wxBG_STYLE_CUSTOM somewhere
 140     in the class initialization code, and that's all you have to do to (mostly)
 141     avoid flicker. The only thing to watch out for is that if you are using
 142     this class together with wxScrolled, you probably do @b not want to call
 143     wxScrolled::PrepareDC() on it as it already does this internally for the
 144     real underlying wxPaintDC.
 145
 146     @library{wxcore}
 147     @category{dc}
 148
 149     @see wxDC, wxBufferedDC, wxAutoBufferedPaintDC, wxPaintDC
 150 */
 151 class wxBufferedPaintDC : public wxBufferedDC
 152 {
 153 public:
 154     //@{
 155     /**
 156         As with wxBufferedDC, you may either provide the bitmap to be used for
 157         buffering or let this object create one internally (in the latter case,
 158         the size of the client part of the window is used).
 159
 160         Pass wxBUFFER_CLIENT_AREA for the @a style parameter to indicate that
 161         just the client area of the window is buffered, or
 162         wxBUFFER_VIRTUAL_AREA to indicate that the buffer bitmap covers the
 163         virtual area.
 164     */
 165     wxBufferedPaintDC(wxWindow* window, wxBitmap& buffer,
 166                       int style = wxBUFFER_CLIENT_AREA);
 167     wxBufferedPaintDC(wxWindow* window,
 168                       int style = wxBUFFER_CLIENT_AREA);
 169     //@}
 170
 171     /**
 172         Copies everything drawn on the DC so far to the window associated with
 173         this object, using a wxPaintDC.
 174     */
 175     ~wxBufferedPaintDC();
 176 };
 177