如何让CDC上输出的文字、图形具有保持功能，集合类CPtrArray的使用，CPaintDC与CClientDC的区别与应用，OnPaint与OnDraw在CView中的关系及实现内幕，滚动窗口的实现，坐标空间，映射方式，设备坐标与逻辑坐标的转换。-CDC on how to output text, graphics have to maintain function, CPtrArray the use of collections, CPaintDC with CClientDC and application of the distinction, OnPaint and OnDraw in CView relations and the realization of the insider, the realization of a rolling window, the coordinates of space, mapping the way device coordinates and logical coordinates conversion.