This class provides a simple way to avoid flicker: when drawing on it, everything is in fact first drawn on an in-memory buffer (a wxBitmap) and then copied to the screen, using the associated wxDC, only once, when this object is destroyed. wxBufferedDC itself is typically associated with wxClientDC, if you want to use it in your EVT_PAINT handler, you should look at wxBufferedPaintDC instead.
When used like this, a valid dc must be specified in the constructor while the buffer bitmap doesn't have to be explicitly provided, by default this class will allocate the bitmap of required size itself. However using a dedicated bitmap can speed up the redrawing process by eliminating the repeated creation and destruction of a possibly big bitmap. Otherwise, wxBufferedDC can be used in the same way as any other device context.
There is another possible use for wxBufferedDC is to use it to maintain a backing store for the window contents. In this case, the associated dc may be NULL but a valid backing store bitmap should be specified.
Finally, please note that GTK+ 2.0 as well as OS X provide double buffering themselves natively. You can either use wxWindow::IsDoubleBuffered to determine whether you need to use buffering or not, or use wxAutoBufferedPaintDC to avoid needless double buffering on the systems which already do it automatically.
wxDC, wxMemoryDC, wxBufferedPaintDC, wxAutoBufferedPaintDC
wxBufferedDC(wxDC *dc, const wxSize& area, int style = wxBUFFER_CLIENT_AREA)
wxBufferedDC(wxDC *dc, wxBitmap& buffer, int style = wxBUFFER_CLIENT_AREA)
If you use the first, default, constructor, you must call one of the Init methods later in order to use the object.
The other constructors initialize the object immediately and Init() must not be called after using them.
void Init(wxDC *dc, const wxSize& area, int style = wxBUFFER_CLIENT_AREA)
void Init(wxDC *dc, wxBitmap& buffer, int style = wxBUFFER_CLIENT_AREA)
These functions initialize the object created using the default constructor. Please see constructors documentation for details.
Copies everything drawn on the DC so far to the underlying DC associated with this object, if any.