wxWidgets/docs/doxygen/overviews/dc.h

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// Name:        dc.h
// Purpose:     topic overview
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
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/*!

 @page overview_dc Device context overview

 Classes: wxBufferedDC, wxBufferedPaintDC, wxDC, wxPostScriptDC,
          wxMetafileDC, wxMemoryDC, wxPrinterDC, wxScreenDC, wxClientDC, 
          wxPaintDC, wxWindowDC.

 A wxDC is a @e device context onto which graphics and text can be drawn.
 The device context is intended to represent a number of output devices in a 
 generic way, with the same API being used throughout.

 Some device contexts are created temporarily in order to draw on a window.
 This is @true of wxScreenDC, wxClientDC, wxPaintDC, and wxWindowDC.
 The following describes the differences between these device contexts and 
 when you should use them.

 @li @b wxScreenDC. Use this to paint on the screen, as opposed to an individual window.
 @li @b wxClientDC. Use this to paint on the client area of window (the part without
     borders and other decorations), but do not use it from within an wxPaintEvent.
 @li @b wxPaintDC. Use this to paint on the client area of a window, but @e only from
     within a wxPaintEvent.
 @li @b wxWindowDC. Use this to paint on the whole area of a window, including decorations.
     This may not be available on non-Windows platforms.

 To use a client, paint or window device context, create an object on the stack with
 the window as argument, for example:

 @code
   void MyWindow::OnMyCmd(wxCommandEvent& event)
   {
     wxClientDC dc(window);
     DrawMyPicture(dc);
   }
 @endcode

 Try to write code so it is parameterised by wxDC - if you do this, the same piece of code may
 write to a number of different devices, by passing a different device context. This doesn't
 work for everything (for example not all device contexts support bitmap drawing) but
 will work most of the time.

*/