ForceRay: Extending Thumb Reach via Force Input Stabilizes Device Grip for Mobile Touch Input

Abstract

Smartphones are used predominantly one-handed, using the thumb for input. Many smartphones, however, have grown beyond 5". Users cannot tap everywhere on these screens without destabilizing their grip. ForceRay (FR) lets users aim at an out-of-reach target by applying a force touch at a comfortable thumb location, casting a virtual ray towards the target. Varying pressure moves a cursor along the ray. When reaching the target, quickly lifting the thumb selects it. In a first study, FR was 195 ms slower and had a 3% higher selection error than the best existing technique, BezelCursor (BC), but FR caused significantly less device movement than all other techniques, letting users maintain a steady grip and removing their concerns about device drops. A second study showed that an hour of training speeds up both BC and FR, and that both are equally fast for targets at the screen border.