First step in background erase optimization

[wxWidgets.git] / docs / latex / wx / bufferdc.tex

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%% Name:        bufferdc.tex
%% Purpose:     wxBufferedDC documentation
%% Author:      Vadim Zeitlin
%% Modified by:
%% Created:     07.02.04
%% RCS-ID:      $Id$
%% Copyright:   (c) 2004 Vadim Zeitlin
%% License:     wxWidgets license
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\section{\class{wxBufferedDC}}\label{wxbuffereddc}

This simple class provides a simple way to avoid flicker: when drawing on it,
everything is in fact first drawn on an in-memory buffer (a 
\helpref{wxBitmap}{wxbitmap}) and then copied to the screen only once, when this
object is destroyed.

It can be used in the same way as any other device context. wxBufferedDC itself
typically replaces \helpref{wxClientDC}{wxclientdc}, if you want to use it in
your \texttt{OnPaint()} handler, you should look at
\helpref{wxBufferedPaintDC}{wxbufferedpaintdc}.

\wxheading{Derived from}

\helpref{wxMemoryDC}{wxmemorydc}\\
\helpref{wxDC}{wxdc}\\
\helpref{wxObject}{wxobject}

\wxheading{Include files}

<wx/dcbuffer.h>

\wxheading{See also}

\helpref{wxDC}{wxdc}


\latexignore{\rtfignore{\wxheading{Members}}}

\membersection{wxBufferedDC::wxBufferedDC}\label{wxbuffereddcctor}

\func{}{wxBufferedDC}{\void}

\func{}{wxBufferedDC}{\param{wxDC *}{dc}, \param{const wxSize\& }{area}}

\func{}{wxBufferedDC}{\param{wxDC *}{dc}, \param{const wxBitmap\& }{buffer}}

If you use the first, default, constructor, you must call one of the 
\helpref{Init}{wxbuffereddcinit} methods later in order to use the object.

The other constructors initialize the object immediately and \texttt{Init()} 
must not be called after using them.

\wxheading{Parameters}

\docparam{dc}{The underlying DC: everything drawn to this object will be
flushed to this DC when this object is destroyed.  You may pass NULL
in order to just initialize the buffer, and not flush it.}

\docparam{area}{The size of the bitmap to be used for buffering (this bitmap is
created internally when it is not given explicitely).}

\docparam{buffer}{Explicitly provided bitmap to be used for buffering: this is
the most efficient solution as the bitmap doesn't have to be recreated each
time but it also requires more memory as the bitmap is never freed. The bitmap
should have appropriate size, anything drawn outside of its bounds is clipped.}


\membersection{wxBufferedDC::Init}\label{wxbuffereddcinit}

\func{void}{Init}{\param{wxDC *}{dc}, \param{const wxSize\& }{area}}

\func{void}{Init}{\param{wxDC *}{dc}, \param{const wxBitmap\& }{buffer}}

These functions initialize the object created using the default constructor.
Please see \helpref{constructors documentation}{wxbuffereddcctor} for details.


% VZ: UnMask() intentionally not documented, we might want to make it private


\membersection{wxBufferedDC::\destruct{wxBufferedDC}}\label{wxbuffereddcdtor}

Copies everything drawn on the DC so far to the underlying DC associated with
this object, if any.


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\section{\class{wxBufferedPaintDC}}\label{wxbufferedpaintdc}

This is a subclass of \helpref{wxBufferedDC}{wxbuffereddc} which can be used
inside of an \texttt{OnPaint()} event handler. Just create an object of this class instead
of \helpref{wxPaintDC}{wxpaintdc} and that's all you have to do to (mostly)
avoid flicker. The only thing to watch out for is that if you are using this
class together with \helpref{wxScrolledWindow}{wxscrolledwindow}, you probably
do \textbf{not} want to call \helpref{PrepareDC}{wxscrolledwindowpreparedc} on it as it
already does this internally for the real underlying wxPaintDC.

\wxheading{Derived from}

\helpref{wxMemoryDC}{wxmemorydc}\\
\helpref{wxDC}{wxdc}\\
\helpref{wxObject}{wxobject}

\wxheading{Include files}

<wx/dcbuffer.h>


\latexignore{\rtfignore{\wxheading{Members}}}

\membersection{wxBufferedPaintDC::wxBufferedPaintDC}\label{wxbufferedpaintdcctor}

\func{}{wxBufferedPaintDC}{\param{wxWindow *}{window}, \param{const wxBitmap\& }{buffer = wxNullBitmap}}

As with \helpref{wxBufferedDC}{wxbuffereddcctor}, you may either provide the
bitmap to be used for buffering or let this object create one internally (in
the latter case, the size of the client part of the window is used).


\membersection{wxBufferedPaintDC::\destruct{wxBufferedPaintDC}}\label{wxbufferedpaintdcdtor}

Copies everything drawn on the DC so far to the window associated with this
object, using a \helpref{wxPaintDC}{wxpaintdc}.