The thumb rest on Quest Pro’s controllers is actually a secret touchpad.
The undocumented feature was discovered by a reverse engineering enthusiast going by the name Shiny Quagsire. He demonstrated the touchpad functionality in a short clip posted to Twitter. Valve’s Index Controllers also feature both a thumbstick and a touchpad.
Meta calls the curved section of the Touch Pro controller face the Thumb Rest. The company only described it as a pressure sensor, saying it can sense up to 6 newtons of force. When combined with input from the index trigger this enables a “precision pinch grip” interaction and the ability to squeeze objects held between your thumb and finger. But at no point did Meta reveal it was also a touchpad, and this input isn’t available in the publicly available APIs.
apparently the Quest Pro controllers have a touchpad, but I can't find literally any documentation on it for some reason aside from "oh, the thumb rest is pressure sensitive" pic.twitter.com/eZzWa7cMxX
— Shiny Quagsire (@ShinyQuagsire) November 8, 2022
This finding begs the question: why on earth would Meta hide this? At the very minimum, it could be useful for enhanced social expression – the Touch Pro controllers also have index finger curl & slide sensing. Beyond this, it could be used for scrolling menus or unique interactions in apps & games.
Perhaps the sensor isn’t reliable enough, or there was some yield issue so it isn’t functional on all manufactured units? Maybe Meta ultimately decided against diverging the input between its mainstream and high-end controllers. Alternatively, the firmware or software behind the feature may not have been ready for launch, so this could be a surprise post-launch new feature.