///////////////////////////////////////////////////////////////////////////// // Name: dcbuffer.h // Purpose: interface of wxBufferedDC // Author: wxWidgets team // RCS-ID: $Id$ // Licence: wxWindows license ///////////////////////////////////////////////////////////////////////////// /** @class wxBufferedDC @wxheader{dcbuffer.h} 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 @c EVT_PAINT handler, you should look at wxBufferedPaintDC instead. When used like this, a valid @e dc must be specified in the constructor while the @e 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 @e 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. @library{wxcore} @category{dc} @see wxDC, wxMemoryDC, wxBufferedPaintDC, wxAutoBufferedPaintDC */ class wxBufferedDC : public wxMemoryDC { public: //@{ /** 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 @c Init() must not be called after using them. @param 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. @param area The size of the bitmap to be used for buffering (this bitmap is created internally when it is not given explicitly). @param 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. @param style wxBUFFER_CLIENT_AREA to indicate that just the client area of the window is buffered, or wxBUFFER_VIRTUAL_AREA to indicate that the buffer bitmap covers the virtual area (in which case PrepareDC is automatically called for the actual window device context). */ wxBufferedDC(); wxBufferedDC(wxDC* dc, const wxSize& area, int style = wxBUFFER_CLIENT_AREA); wxBufferedDC(wxDC* dc, wxBitmap& buffer, int style = wxBUFFER_CLIENT_AREA); //@} /** Copies everything drawn on the DC so far to the underlying DC associated with this object, if any. */ //@{ /** These functions initialize the object created using the default constructor. Please see @ref ctor() "constructors documentation" for details. */ void Init(wxDC* dc, const wxSize& area, int style = wxBUFFER_CLIENT_AREA); void Init(wxDC* dc, wxBitmap& buffer, int style = wxBUFFER_CLIENT_AREA); //@} }; /** @class wxAutoBufferedPaintDC @wxheader{dcbuffer.h} This wxDC derivative can be used inside of an @c OnPaint() event handler to achieve double-buffered drawing. Just create an object of this class instead of wxPaintDC and make sure wxWindow::SetBackgroundStyle is called with wxBG_STYLE_CUSTOM somewhere in the class initialization code, and that's all you have to do to (mostly) avoid flicker. The difference between wxBufferedPaintDC and this class, is the lightweigthness - on platforms which have native double-buffering, wxAutoBufferedPaintDC is simply a typedef of wxPaintDC. Otherwise, it is a typedef of wxBufferedPaintDC. @library{wxbase} @category{dc} @see wxDC, wxBufferedPaintDC */ class wxAutoBufferedPaintDC : public wxBufferedPaintDC { public: /** Constructor. Pass a pointer to the window on which you wish to paint. */ wxAutoBufferedPaintDC(wxWindow* window); }; /** @class wxBufferedPaintDC @wxheader{dcbuffer.h} This is a subclass of wxBufferedDC which can be used inside of an @c OnPaint() event handler. Just create an object of this class instead of wxPaintDC and make sure wxWindow::SetBackgroundStyle is called with wxBG_STYLE_CUSTOM somewhere in the class initialization code, 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 wxScrolledWindow, you probably do @b not want to call wxScrolledWindow::PrepareDC on it as it already does this internally for the real underlying wxPaintDC. @library{wxcore} @category{dc} @see wxDC, wxBufferedDC, wxAutoBufferedPaintDC */ class wxBufferedPaintDC : public wxBufferedDC { public: //@{ /** As with @ref wxBufferedDC::ctor wxBufferedDC, 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). Pass wxBUFFER_CLIENT_AREA for the @a style parameter to indicate that just the client area of the window is buffered, or wxBUFFER_VIRTUAL_AREA to indicate that the buffer bitmap covers the virtual area (in which case PrepareDC is automatically called for the actual window device context). */ wxBufferedPaintDC(wxWindow* window, wxBitmap& buffer, int style = wxBUFFER_CLIENT_AREA); wxBufferedPaintDC(wxWindow* window, int style = wxBUFFER_CLIENT_AREA); //@} /** Copies everything drawn on the DC so far to the window associated with this object, using a wxPaintDC. */ };