解决改变窗口的大小时，窗口内容会闪烁的问题。这个类库使用不擦除背景而在内存中作图，然后拷贝到窗口的原理。-Solve the changing size of the window, the window contents will flicker problem. This library does not erase the background while using the mapping in memory and then copied to the principles of the window.