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{Library}
  50
  51 \helpref{wxCore}{librarieslist}
  52
  53 \wxheading{See also}
  54
  55 \helpref{wxDC}{wxdc},\rtfsp
  56 \helpref{wxMemoryDC}{wxmemorydc},\rtfsp
  57 \helpref{wxBufferedPaintDC}{wxbufferedpaintdc},\rtfsp
  58 \helpref{wxAutoBufferedPaintDC}{wxautobufferedpaintdc}
  59
  60
  61 \latexignore{\rtfignore{\wxheading{Members}}}
  62
  63 \membersection{wxBufferedDC::wxBufferedDC}\label{wxbuffereddcctor}
  64
  65 \func{}{wxBufferedDC}{\void}
  66
  67 \func{}{wxBufferedDC}{\param{wxDC *}{dc}, \param{const wxSize\& }{area}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
  68
  69 \func{}{wxBufferedDC}{\param{wxDC *}{dc}, \param{wxBitmap\& }{buffer}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
  70
  71 If you use the first, default, constructor, you must call one of the
  72 \helpref{Init}{wxbuffereddcinit} methods later in order to use the object.
  73
  74 The other constructors initialize the object immediately and \texttt{Init()}
  75 must not be called after using them.
  76
  77 \wxheading{Parameters}
  78
  79 \docparam{dc}{The underlying DC: everything drawn to this object will be
  80 flushed to this DC when this object is destroyed.  You may pass NULL
  81 in order to just initialize the buffer, and not flush it.}
  82
  83 \docparam{area}{The size of the bitmap to be used for buffering (this bitmap is
  84 created internally when it is not given explicitly).}
  85
  86 \docparam{buffer}{Explicitly provided bitmap to be used for buffering: this is
  87 the most efficient solution as the bitmap doesn't have to be recreated each
  88 time but it also requires more memory as the bitmap is never freed. The bitmap
  89 should have appropriate size, anything drawn outside of its bounds is clipped.}
  90
  91 \docparam{style}{wxBUFFER\_CLIENT\_AREA to indicate that just the client area of
  92 the window is buffered, or wxBUFFER\_VIRTUAL\_AREA to indicate that the buffer bitmap
  93 covers the virtual area (in which case PrepareDC is automatically called for the actual window
  94 device context).}
  95
  96 \membersection{wxBufferedDC::Init}\label{wxbuffereddcinit}
  97
  98 \func{void}{Init}{\param{wxDC *}{dc}, \param{const wxSize\& }{area}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
  99
 100 \func{void}{Init}{\param{wxDC *}{dc}, \param{wxBitmap\& }{buffer}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
 101
 102 These functions initialize the object created using the default constructor.
 103 Please see \helpref{constructors documentation}{wxbuffereddcctor} for details.
 104
 105
 106 % VZ: UnMask() intentionally not documented, we might want to make it private
 107
 108
 109 \membersection{wxBufferedDC::\destruct{wxBufferedDC}}\label{wxbuffereddcdtor}
 110
 111 Copies everything drawn on the DC so far to the underlying DC associated with
 112 this object, if any.
 113
 114
 115 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 116
 117 \section{\class{wxBufferedPaintDC}}\label{wxbufferedpaintdc}
 118
 119 This is a subclass of \helpref{wxBufferedDC}{wxbuffereddc} which can be used
 120 inside of an \texttt{OnPaint()} event handler. Just create an object of this class instead
 121 of \helpref{wxPaintDC}{wxpaintdc} and make sure \helpref{wxWindow::SetBackgroundStyle}{wxwindowgetbackgroundstyle}
 122 is called with wxBG\_STYLE\_CUSTOM somewhere in the class initialization code, and that's all
 123 you have to do to (mostly) avoid flicker. The only thing to watch out for is that if you are
 124 using this class together with \helpref{wxScrolledWindow}{wxscrolledwindow}, you probably
 125 do \textbf{not} want to call \helpref{PrepareDC}{wxscrolledwindowpreparedc} on it as it
 126 already does this internally for the real underlying wxPaintDC.
 127
 128 \wxheading{Derived from}
 129
 130 \helpref{wxBufferedDC}{wxbuffereddc}\\
 131 \helpref{wxMemoryDC}{wxmemorydc}\\
 132 \helpref{wxDC}{wxdc}\\
 133 \helpref{wxObject}{wxobject}
 134
 135 \wxheading{Include files}
 136
 137 <wx/dcbuffer.h>
 138
 139 \wxheading{Library}
 140
 141 \helpref{wxCore}{librarieslist}
 142
 143 \wxheading{See also}
 144
 145 \helpref{wxDC}{wxdc},\rtfsp
 146 \helpref{wxBufferedDC}{wxbuffereddc},\rtfsp
 147 \helpref{wxAutoBufferedPaintDC}{wxautobufferedpaintdc}
 148
 149
 150 \latexignore{\rtfignore{\wxheading{Members}}}
 151
 152 \membersection{wxBufferedPaintDC::wxBufferedPaintDC}\label{wxbufferedpaintdcctor}
 153
 154 \func{}{wxBufferedPaintDC}{\param{wxWindow *}{window}, \param{wxBitmap\& }{buffer}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
 155
 156 \func{}{wxBufferedPaintDC}{\param{wxWindow *}{window}, \param{int }{style = wxBUFFER\_CLIENT\_AREA}}
 157
 158 As with \helpref{wxBufferedDC}{wxbuffereddcctor}, you may either provide the
 159 bitmap to be used for buffering or let this object create one internally (in
 160 the latter case, the size of the client part of the window is used).
 161
 162 Pass wxBUFFER\_CLIENT\_AREA for the {\it style} parameter to indicate that just the client area of
 163 the window is buffered, or wxBUFFER\_VIRTUAL\_AREA to indicate that the buffer bitmap
 164 covers the virtual area (in which case PrepareDC is automatically called for the actual window
 165 device context).
 166
 167 \membersection{wxBufferedPaintDC::\destruct{wxBufferedPaintDC}}\label{wxbufferedpaintdcdtor}
 168
 169 Copies everything drawn on the DC so far to the window associated with this
 170 object, using a \helpref{wxPaintDC}{wxpaintdc}.
 171
 172
 173 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 174
 175 \section{\class{wxAutoBufferedPaintDC}}\label{wxautobufferedpaintdc}
 176
 177 This wxDC derivative can be used inside of an \texttt{OnPaint()} event handler to achieve
 178 double-buffered drawing. Just create an object of this class instead of \helpref{wxPaintDC}{wxpaintdc}
 179 and make sure \helpref{wxWindow::SetBackgroundStyle}{wxwindowgetbackgroundstyle} is called
 180 with wxBG\_STYLE\_CUSTOM somewhere in the class initialization code, and that's all you have
 181 to do to (mostly) avoid flicker.
 182
 183 The difference between \helpref{wxBufferedPaintDC}{wxbufferedpaintdc} and this class,
 184 is the lightweigthness - on platforms which have native double-buffering, wxAutoBufferedPaintDC is simply
 185 a typedef of wxPaintDC. Otherwise, it is a typedef of wxBufferedPaintDC.
 186
 187
 188 \wxheading{Derived from}
 189
 190 \helpref{wxBufferedPaintDC}{wxbufferedpaintdc}\\
 191 \helpref{wxBufferedDC}{wxbuffereddc}\\
 192 \helpref{wxMemoryDC}{wxmemorydc}\\
 193 \helpref{wxDC}{wxdc}\\
 194 \helpref{wxObject}{wxobject}
 195
 196 \wxheading{Include files}
 197
 198 <wx/dcbuffer.h>
 199
 200 \wxheading{See also}
 201
 202 \helpref{wxDC}{wxdc},\rtfsp
 203 \helpref{wxBufferedPaintDC}{wxbufferedpaintdc}
 204
 205
 206 \latexignore{\rtfignore{\wxheading{Members}}}
 207
 208 \membersection{wxAutoBufferedPaintDC::wxAutoBufferedPaintDC}\label{wxautobufferedpaintdcctor}
 209
 210 \func{}{wxAutoBufferedPaintDC}{\param{wxWindow *}{window}}
 211
 212 Constructor. Pass a pointer to the window on which you wish to paint.
 213