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