Gesture-enhanced single-touch, also known as "dual control", "gesture touch", and often "dual-touch", describes the ability of a
touchscreen
A touchscreen (or touch screen) is a type of electronic visual display, display that can detect touch input from a user. It consists of both an input device (a touch panel) and an output device (a visual display). The touch panel is typically l ...
to register certain two-finger
gestures
A gesture is a form of nonverbal communication or non-vocal communication in which visible bodily actions communicate particular messages, either in place of, or in conjunction with, speech. Gestures include movement of the hands, face, or othe ...
, despite lacking hardware that would allow it to fully register all two-finger movements. A very common application of gesture-enhanced single-touch technology is the
pinch-to-zoom gesture, which allows the user to zoom in or out by moving two fingers farther apart or closer together while touching the display.
Technical background
An important technical reason for the limitation to gesture-enhanced single-touch instead of allowing dual-touch or
multi-touch
In computing, multi-touch is technology that enables a surface (a touchpad or touchscreen) to recognize the presence of more than one somatosensory system, point of contact with the surface at the same time. The origins of multitouch began at CE ...
is the type of sensor hardware in the display. Many
touchscreen technologies obtain two independent measurements per touch to acquire a 2-dimensional position. Given two distinct touches, however, this returns two pairs of measurements, which can be combined in two ways, producing an ambiguous result. Thus, it is not possible to exactly determine the position of two distinct touches. Still, the average position can be approximated, as well as the distance between the touches, which suffices for some gesture applications.
See also
*
Multi-touch
In computing, multi-touch is technology that enables a surface (a touchpad or touchscreen) to recognize the presence of more than one somatosensory system, point of contact with the surface at the same time. The origins of multitouch began at CE ...
References
External links
Annotated Bibliography of References to Gestures, Touchscreens, and Pen Computingby Jean Renard Ward
Touchscreens
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