How to get 'CTRL + LEFT_DOWN' on ScreenSpaceEventHandler

1. A concise explanation of the problem you’re experiencing.

I should get the the ‘camera.heading’ and the ‘camera.pitch’ every time it’s changed, with ‘CTRL + LEFT mouse button’

How can I get it from “ScreenSpaceEventHandler”?

4. The Cesium version you’re using, your operating system and browser.

1.62