https://www.theverge.com/circuitbreaker/2019/1/17/18187776/xiaomi-bigger-in-display-fingerprint-sensor

Xiaomi has been slower to adopt in-display fingerprint sensors than some of its Chinese rivals, only including the feature on certain high-end variants of last year's Mi 8 flagship phone. But according to a Weibo post by president and co-founder Lin Bin, the company is working on a much more advanced implementation of the technology.

Lin's post includes a video demonstrating a prototype phone with a new fingerprint sensor that has an active area of 25 x 50mm, meaning users could unlock it by tapping anywhere within a much larger region than the thumbprint-sized scanners found on several phones released last year. It would represent a boon for usability, particularly since you wouldn’t have to look for the physical location of the scanner while picking up the phone. Lin also says the new sensor is able to wake and unlock the phone with a single tap.