Chinese smartphone makers Oppo and Xiaomi both teased under-screen selfie cameras earlier this month, but Oppo just beat Xiaomi to the punch in officially announcing and demonstrating it. Rather than use a notch cut out from the display for a camera, reducing the available screen real estate, Oppo’s new camera is found behind the display itself, allowing 100% of the front surface to be used for the screen. When the camera is activated, the top portion of the display goes…