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 @a 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 style
  64             wxBUFFER_CLIENT_AREA to indicate that just the client area of the
  65             window is buffered, or wxBUFFER_VIRTUAL_AREA to indicate that the
  66             buffer bitmap covers the virtual area.
  67     */
  68     wxBufferedDC(wxDC* dc, const wxSize& area,
  69                  int style = wxBUFFER_CLIENT_AREA);
  70
  71     /**
  72         Creates a buffer for the provided dc. Init() must not be called when
  73         using this constructor.
  74
  75         @param dc
  76             The underlying DC: everything drawn to this object will be flushed
  77             to this DC when this object is destroyed. You may pass @NULL in
  78             order to just initialize the buffer, and not flush it.
  79         @param buffer
  80             Explicitly provided bitmap to be used for buffering: this is the
  81             most efficient solution as the bitmap doesn't have to be recreated
  82             each time but it also requires more memory as the bitmap is never
  83             freed. The bitmap should have appropriate size, anything drawn
  84             outside of its bounds is clipped.
  85         @param style
  86             wxBUFFER_CLIENT_AREA to indicate that just the client area of the
  87             window is buffered, or wxBUFFER_VIRTUAL_AREA to indicate that the
  88             buffer bitmap covers the virtual area.
  89     */
  90     wxBufferedDC(wxDC* dc, wxBitmap& buffer = wxNullBitmap,
  91                  int style = wxBUFFER_CLIENT_AREA);
  92     //@}
  93
  94     /**
  95         Copies everything drawn on the DC so far to the underlying DC
  96         associated with this object, if any.
  97     */
  98     virtual ~wxBufferedDC();
  99
 100     //@{
 101     /**
 102         Initializes the object created using the default constructor. Please
 103         see the constructors for parameter details.
 104     */
 105     void Init(wxDC* dc, const wxSize& area,
 106               int style = wxBUFFER_CLIENT_AREA);
 107     void Init(wxDC* dc, wxBitmap& buffer = wxNullBitmap,
 108               int style = wxBUFFER_CLIENT_AREA);
 109     //@}
 110 };
 111
 112
 113
 114 /**
 115     @class wxAutoBufferedPaintDC
 116
 117     This wxDC derivative can be used inside of an @c EVT_PAINT() event handler
 118     to achieve double-buffered drawing. Just use this class instead of
 119     wxPaintDC and make sure wxWindow::SetBackgroundStyle() is called with
 120     wxBG_STYLE_CUSTOM somewhere in the class initialization code, and that's
 121     all you have to do to (mostly) avoid flicker.
 122
 123     The difference between wxBufferedPaintDC and this class is that this class
 124     won't double-buffer on platforms which have native double-buffering
 125     already, avoiding any unneccessary buffering to avoid flicker.
 126
 127     wxAutoBufferedPaintDC is simply a typedef of wxPaintDC on platforms that
 128     have native double-buffering, otherwise, it is a typedef of
 129     wxBufferedPaintDC.
 130
 131     @library{wxbase}
 132     @category{dc}
 133
 134     @see wxDC, wxBufferedPaintDC, wxPaintDC
 135 */
 136 class wxAutoBufferedPaintDC : public wxBufferedPaintDC
 137 {
 138 public:
 139     /**
 140         Constructor. Pass a pointer to the window on which you wish to paint.
 141     */
 142     wxAutoBufferedPaintDC(wxWindow* window);
 143 };
 144
 145
 146
 147 /**
 148     @class wxBufferedPaintDC
 149
 150     This is a subclass of wxBufferedDC which can be used inside of an
 151     @c EVT_PAINT() event handler to achieve double-buffered drawing. Just use
 152     this class instead of wxPaintDC and make sure
 153     wxWindow::SetBackgroundStyle() is called with wxBG_STYLE_CUSTOM somewhere
 154     in the class initialization code, and that's all you have to do to (mostly)
 155     avoid flicker. The only thing to watch out for is that if you are using
 156     this class together with wxScrolled, you probably do @b not want to call
 157     wxScrolled::PrepareDC() on it as it already does this internally for the
 158     real underlying wxPaintDC.
 159
 160     @library{wxcore}
 161     @category{dc}
 162
 163     @see wxDC, wxBufferedDC, wxAutoBufferedPaintDC, wxPaintDC
 164 */
 165 class wxBufferedPaintDC : public wxBufferedDC
 166 {
 167 public:
 168     //@{
 169     /**
 170         As with wxBufferedDC, you may either provide the bitmap to be used for
 171         buffering or let this object create one internally (in the latter case,
 172         the size of the client part of the window is used).
 173
 174         Pass wxBUFFER_CLIENT_AREA for the @a style parameter to indicate that
 175         just the client area of the window is buffered, or
 176         wxBUFFER_VIRTUAL_AREA to indicate that the buffer bitmap covers the
 177         virtual area.
 178     */
 179     wxBufferedPaintDC(wxWindow* window, wxBitmap& buffer,
 180                       int style = wxBUFFER_CLIENT_AREA);
 181     wxBufferedPaintDC(wxWindow* window,
 182                       int style = wxBUFFER_CLIENT_AREA);
 183     //@}
 184
 185     /**
 186         Copies everything drawn on the DC so far to the window associated with
 187         this object, using a wxPaintDC.
 188     */
 189     virtual ~wxBufferedPaintDC();
 190 };
 191