如何打印所有WKWebView On和Offscreen内容OSX和iOS

This question is about printing ALL content (including off screen content) of WKWebView. Currently (still, as of iOS 10.2 or OSX 10.12) there is NO working solution and none of the supposed solutions on Stackoverflow work. Only provide an answer here if you have verified for yourself that you can print OFF SCREEN CONTENT, and if you did then provide the working example code.This question is about printing ALL content (in