GetBoundsRect The GetBoundsRect function obtains the current accumulated bounding rectangle for a specified device context. The system maintains an accumulated bounding rectangle for each application. An application can retrieve and set this rectangle.
然后根据RECT就可以得到长宽
的gdi函数操作范围是不一样的！
DC的一些参数都在这里了
The GetBoundsRect function obtains the current accumulated bounding rectangle for a specified device context. The system maintains an accumulated bounding rectangle for each application. An application can retrieve and set this rectangle.