If you have ever drawn something in the window by yourself then you know about flickering. The right solution to get rid of it is to use double-buffering by creating the off-screen bitmap, painting there and copying the bitmap to the window. This is pretty simple technique, but you can use this class to minimize your handwork.
The technique is really simple. Create memory DC using
CreateCompatibleDC() function, then create the bitmap of desired size and select it to the memory DC by using
SelectObject() function. Draw on the memory DC and copy the result to the window DC with
BitBlt(). The trick is to create right bitmap. I use
CreateBitmap() function to specify correct BPP value.
Using the Code
To start using
CakBufferedDC class just declare the object of it. Note that this class was designed to use only in
WM_PAINT message handler (
OnPaint method of
CWnd). It will automatically call
dc.DrawText(_T("Hello world"), &dc.ClientRect(), DT_VCENTER|DT_SINGLELINE);
When the object of
CakBufferedDC will be destroyed, it will automatically copy your painting to the window. Only region that needs an update will be copied.
CakBufferedDC is a
CDC descendant, you will be able to use all methods of
CDC class (with the exception of
Detach() for obvious reasons) and pass the object of
CakBufferedDC to API functions that expect variable of type
HDC. If you didn't use things like
MyPaintDC.m_hDC then your code won't feel the difference.
The class also provides you with
UpdateRect() methods which return client rectangle of the window, window's rectangle and rectangle that needs an update respectively.