A patent filed by Xiaomi for a full-screen smartphone utilizing an under-display camera has been unearthed. The patent application was made with the State Intellectual Property Office of China in November 2018, and it briefly describes Xiaomi's solution for the feature, which appears to involve the smartphone using two screens.
https://www.notebookcheck.net/Xiaomi-could-beat-Samsung-in-producing-a-full-screen-smartphone-with-an-under-display-camera.422924.0.html
Shooting through the displace panel is a dumb idea. The light loss is likely to be several stops at least, which will only make the (generally) poor quality selfie images look even worse in low-light indoor shots.
Then again, I'm not a selfie cam whore. Just a photog who knows his stuff.