Microsoft’s Shift uses call-outs to deal with the problem of fingers covering targets on touchscreen devices.
“Retrieving the stylus of a pen-based device takes time and requires a second hand. Especially for short, intermittent interactions many users therefore choose to use their bare fingers instead. Although convenient, this increases targeting times and error rates. We argue that the main reason is the occlusion of the target by the user’s finger. We propose a pointing technique we call Shift that is designed to address this issue. When the user touches the screen, Shift creates a callout showing a copy of the occluded screen area and places it in a non-occluded location. The callout also shows a pointer representing the hotspot of the finger. Using this visual feedback, users guide the pointer into the target by moving their finger on the screen surface and commit the target acquisition by lifting the finger. Over large targets, in contrast, no callout is created and users enjoy the full performance of an unaltered touch screen.”