Touch scrolling transfer functions

Abstract

Figure 1. Transfer functions transform touch scrolling gestures (top) into scrolling output. These gestures can be simulated mechanically by SCARA robots (bottom) to reverse engineer the transfer functions. ABSTRACTTouch scrolling systems use a transfer function to transform gestures on a touch sensitive surface into scrolling output. The design of these transfer functions is complex as they must facilitate precise direct manipulation of the underlying content as well as rapid scrolling through large datasets. However, researchers' ability to refine them is impaired by: (1) limited understanding of how users express scrolling intentions through touch gestures; (2) lack of knowledge on proprietary transfer functions, causing researchers to evaluate techniques that may misrepresent the state of the art; and (3) a lack of tools for examining existing transfer functions. To address these limitations, we examine how users express scrolling intentions in a human factors experiment; we describe methods to reverse engineer existing 'black box' transfer functions, including use of an accurate robotic arm; and we use the methods to expose the functions of Apple iOS and Google Android, releasing data tables and software to assist replication. We discuss how this new understanding can improve experimental rigour and assist iterative improvement of touch scrolling.

Control Theoretic Models of Pointing

“…This can include properties such as feedback delays, sensor noise (see e.g., [54]), or interaction effects like 'sticky mouse' dynamics, isometric joystick dynamics [2], magnification effects, inertia, fisheye lenses, speed-dependent zooming, all of which can be readily represented by dynamic models. The use of state space control methods was explored in document zooming context in [16][17][18][19]31] and [44] reviewed the challenge of optimising scrolling transfer functions and used a robot arm to identify the dynamics of commercial products. Examples of the use of dynamic models in interactive systems are now widespread in commercial systems, and there are also examples in the academic literature, including [8,59].…”

Adaptive Kinetic Scrolling: Kinetic Scrolling for Large Datasets on Mobile Devices

“…This clutch time indicates the time interval between scrolling actions. With a touch-based device, the clutch time is a reliable indicator of the intended scrolling velocity, with users increasing their gesture frequency to express a desire for faster scrolling [27]. In other words, a short clutch time implies that the user is repeatedly scrolling rapidly.…”

“…Kinetic scrolling speed exhibits an exponential regression curve based on the frictional effect. Scrolling velocity decelerated by friction is implemented in the form of an exponential decay factor [27]. The variable denotes the elapsed time, and the constants depend on the mobile device and Operating System.…”

Content-aware kinetic scrolling for supporting web page navigation

“…This technique has been implemented in most modern touchscreen devices. Flicking is a throwing-like gesture that invokes a transfer function [14], which turns kinetic scrolling into automatic scrolling with inertia. The inertial effect provides a natural and physical affordance for scrolling, and enables more precise scrolling control.…”