这是一个在做浏览器的时候必备功能，但窗口的大小不能固定时，通常我们都会使用计算公式去判断更变，属于自己去创作函数，但该源码是调用windows自带的API，无需繁杂的数学计算，不用到每个组件都加上时间，只需提供一个宽高值即可自适应变动，不至于界面十分混乱。-This is a necessary when doing the browser capabilities, but the size of the window can not be fixed, we usually use calculation formula to determine more change, to create their own functions, but the source is the API calls the Windows, without complex mathematical calculation, not to each component plus time, only need to provide a wide high value adaptive changes, not interface of chaos.