docs/latex/wx/bufferdc.tex

   1 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   2 %% Name:        bufferdc.tex
   3 %% Purpose:     wxBufferedDC documentation
   4 %% Author:      Vadim Zeitlin
   5 %% Modified by:
   6 %% Created:     07.02.04
   7 %% RCS-ID:      $Id$
   8 %% Copyright:   (c) 2004 Vadim Zeitlin
   9 %% License:     wxWindows license
  10 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  11
  12 \section{\class{wxBufferedDC}}\label{wxbuffereddc}
  13
  14 This class provides a simple way to avoid flicker: when drawing on it,
  15 everything is in fact first drawn on an in-memory buffer (a
  16 \helpref{wxBitmap}{wxbitmap}) and then copied to the screen, using the
  17 associated wxDC, only once, when this object is destroyed. wxBufferedDC itself
  18 is typically associated with \helpref{wxClientDC}{wxclientdc}, if you want to
  19 use it in your \texttt{EVT\_PAINT} handler, you should look at
  20 \helpref{wxBufferedPaintDC}{wxbufferedpaintdc} instead.
  21
  22 When used like this, a valid \arg{dc} must be specified in the constructor
  23 while the \arg{buffer} bitmap doesn't have to be explicitly provided, by
  24 default this class will allocate the bitmap of required size itself. However
  25 using a dedicated bitmap can speed up the redrawing process by eliminating the
  26 repeated creation and destruction of a possibly big bitmap. Otherwise,
  27 wxBufferedDC can be used in the same way as any other device context.
  28
  29 There is another possible use for wxBufferedDC is to use it to maintain a
  30 backing store for the window contents. In this case, the associated \arg{dc}
  31 may be \NULL but a valid backing store bitmap should be specified.
  32
  33 Finally, please note that GTK+ 2.0 as well as OS X provide double buffering
  34 themselves natively. You can either use \helpref{wxWindow::IsDoubleBuffered}{wxwindowisdoublebuffered}
  35 to determine whether you need to use buffering or not, or use
  36 \helpref{wxAutoBufferedPaintDC}{wxautobufferedpaintdc} to avoid needless double
  37 buffering on the systems which already do it automatically.
  38
  39 \wxheading{Derived from}
  40
  41 \helpref{wxMemoryDC}{wxmemorydc}\\
  42 \helpref{wxDC}{wxdc}\\
  43 \helpref{wxObject}{wxobject}
  44
  45 \wxheading{Include files}
  46
  47 <wx/dcbuffer.h>
  48
  49 \wxheading{See also}
  50
  51 \helpref{wxDC}{wxdc},\rtfsp
  52 \helpref{wxMemoryDC}{wxmemorydc},\rtfsp
  53 \helpref{wxBufferedPaintDC}{wxbufferedpaintdc},\rtfsp
  54 \helpref{wxAutoBufferedPaintDC}{wxautobufferedpaintdc}
  55
  56
  57 \latexignore{\rtfignore{\wxheading{Members}}}
  58
  59 \membersection{wxBufferedDC::wxBufferedDC}\label{wxbuffereddcctor}
  60
  61 \func{}{wxBufferedDC}{\void}
  62
  63 \func{}{wxBufferedDC}{\param{wxDC *}{dc}, \param{const wxSize\& }{area}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
  64
  65 \func{}{wxBufferedDC}{\param{wxDC *}{dc}, \param{const wxBitmap\& }{buffer}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
  66
  67 If you use the first, default, constructor, you must call one of the
  68 \helpref{Init}{wxbuffereddcinit} methods later in order to use the object.
  69
  70 The other constructors initialize the object immediately and \texttt{Init()}
  71 must not be called after using them.
  72
  73 \wxheading{Parameters}
  74
  75 \docparam{dc}{The underlying DC: everything drawn to this object will be
  76 flushed to this DC when this object is destroyed.  You may pass NULL
  77 in order to just initialize the buffer, and not flush it.}
  78
  79 \docparam{area}{The size of the bitmap to be used for buffering (this bitmap is
  80 created internally when it is not given explicitly).}
  81
  82 \docparam{buffer}{Explicitly provided bitmap to be used for buffering: this is
  83 the most efficient solution as the bitmap doesn't have to be recreated each
  84 time but it also requires more memory as the bitmap is never freed. The bitmap
  85 should have appropriate size, anything drawn outside of its bounds is clipped.}
  86
  87 \docparam{style}{wxBUFFER\_CLIENT\_AREA to indicate that just the client area of
  88 the window is buffered, or wxBUFFER\_VIRTUAL\_AREA to indicate that the buffer bitmap
  89 covers the virtual area (in which case PrepareDC is automatically called for the actual window
  90 device context).}
  91
  92 \membersection{wxBufferedDC::Init}\label{wxbuffereddcinit}
  93
  94 \func{void}{Init}{\param{wxDC *}{dc}, \param{const wxSize\& }{area}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
  95
  96 \func{void}{Init}{\param{wxDC *}{dc}, \param{const wxBitmap\& }{buffer}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
  97
  98 These functions initialize the object created using the default constructor.
  99 Please see \helpref{constructors documentation}{wxbuffereddcctor} for details.
 100
 101
 102 % VZ: UnMask() intentionally not documented, we might want to make it private
 103
 104
 105 \membersection{wxBufferedDC::\destruct{wxBufferedDC}}\label{wxbuffereddcdtor}
 106
 107 Copies everything drawn on the DC so far to the underlying DC associated with
 108 this object, if any.
 109
 110
 111 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 112
 113 \section{\class{wxBufferedPaintDC}}\label{wxbufferedpaintdc}
 114
 115 This is a subclass of \helpref{wxBufferedDC}{wxbuffereddc} which can be used
 116 inside of an \texttt{OnPaint()} event handler. Just create an object of this class instead
 117 of \helpref{wxPaintDC}{wxpaintdc} and make sure \helpref{wxWindow::SetBackgroundStyle}{wxwindowgetbackgroundstyle}
 118 is called with wxBG\_STYLE\_CUSTOM somewhere in the class initialization code, and that's all
 119 you have to do to (mostly) avoid flicker. The only thing to watch out for is that if you are
 120 using this class together with \helpref{wxScrolledWindow}{wxscrolledwindow}, you probably
 121 do \textbf{not} want to call \helpref{PrepareDC}{wxscrolledwindowpreparedc} on it as it
 122 already does this internally for the real underlying wxPaintDC.
 123
 124 \wxheading{Derived from}
 125
 126 \helpref{wxBufferedDC}{wxbuffereddc}\\
 127 \helpref{wxMemoryDC}{wxmemorydc}\\
 128 \helpref{wxDC}{wxdc}\\
 129 \helpref{wxObject}{wxobject}
 130
 131 \wxheading{Include files}
 132
 133 <wx/dcbuffer.h>
 134
 135 \wxheading{See also}
 136
 137 \helpref{wxDC}{wxdc},\rtfsp
 138 \helpref{wxBufferedDC}{wxbuffereddc},\rtfsp
 139 \helpref{wxAutoBufferedPaintDC}{wxautobufferedpaintdc}
 140
 141
 142 \latexignore{\rtfignore{\wxheading{Members}}}
 143
 144 \membersection{wxBufferedPaintDC::wxBufferedPaintDC}\label{wxbufferedpaintdcctor}
 145
 146 \func{}{wxBufferedPaintDC}{\param{wxWindow *}{window}, \param{const wxBitmap\& }{buffer}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
 147
 148 \func{}{wxBufferedPaintDC}{\param{wxWindow *}{window}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
 149
 150 As with \helpref{wxBufferedDC}{wxbuffereddcctor}, you may either provide the
 151 bitmap to be used for buffering or let this object create one internally (in
 152 the latter case, the size of the client part of the window is used).
 153
 154 Pass wxBUFFER\_CLIENT\_AREA for the {\it style} parameter to indicate that just the client area of
 155 the window is buffered, or wxBUFFER\_VIRTUAL\_AREA to indicate that the buffer bitmap
 156 covers the virtual area (in which case PrepareDC is automatically called for the actual window
 157 device context).
 158
 159 \membersection{wxBufferedPaintDC::\destruct{wxBufferedPaintDC}}\label{wxbufferedpaintdcdtor}
 160
 161 Copies everything drawn on the DC so far to the window associated with this
 162 object, using a \helpref{wxPaintDC}{wxpaintdc}.
 163
 164
 165 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 166
 167 \section{\class{wxAutoBufferedPaintDC}}\label{wxautobufferedpaintdc}
 168
 169 This wxDC derivative can be used inside of an \texttt{OnPaint()} event handler to achieve
 170 double-buffered drawing. Just create an object of this class instead of \helpref{wxPaintDC}{wxpaintdc}
 171 and make sure \helpref{wxWindow::SetBackgroundStyle}{wxwindowgetbackgroundstyle} is called
 172 with wxBG\_STYLE\_CUSTOM somewhere in the class initialization code, and that's all you have
 173 to do to (mostly) avoid flicker.
 174
 175 The difference between \helpref{wxBufferedPaintDC}{wxbufferedpaintdc} and this class,
 176 is the lightweigthness - on platforms which have native double-buffering, wxAutoBufferedPaintDC is simply
 177 a typedef of wxPaintDC. Otherwise, it is a typedef of wxBufferedPaintDC.
 178
 179
 180 \wxheading{Derived from}
 181
 182 \helpref{wxBufferedPaintDC}{wxbufferedpaintdc}\\
 183 \helpref{wxPaintDC}{wxpaintdc}\\
 184 \helpref{wxDC}{wxdc}\\
 185 \helpref{wxObject}{wxobject}
 186
 187 \wxheading{Include files}
 188
 189 <wx/dcbuffer.h>
 190
 191 \wxheading{See also}
 192
 193 \helpref{wxDC}{wxdc},\rtfsp
 194 \helpref{wxBufferedPaintDC}{wxbufferedpaintdc}
 195
 196
 197 \latexignore{\rtfignore{\wxheading{Members}}}
 198
 199 \membersection{wxAutoBufferedPaintDC::wxAutoBufferedPaintDC}\label{wxautobufferedpaintdcctor}
 200
 201 \func{}{wxAutoBufferedPaintDC}{\param{wxWindow *}{window}}
 202
 203 Constructor. Pass a pointer to the window on which you wish to paint.
 204