问题
How to grab a screenshot of a DirectX window that is not in foreground and doesn't have focus. I want to monitor what happens with application in the background, but without switching to it.
The standard way with PrintWindow doesn't work. You can test that on Unity apps, for example.
来源：https://stackoverflow.com/questions/30694056/make-screenshot-of-directx-window-that-is-hidden-and-doesnt-have-focus