Philip I.S. Lei and Angus K.Y. Wong, Macau Polytechnic Institute Because of their intuitive interaction styles, multiple-touch devices could trigger a revolution in user interfaces. But how can designers advance this technology? T he window, icon, menu, and pointer (WIMP) interface built for single-touch pointing devices has long been estab- lished as the standard GUI in desktop operating systems and is also prevalent in mobile devices, such as personal digital assistants and smartphones. However, this approach offers limited actions for GUI designers, a fact that becomes more ob- vious when using an application with a sophis- ticated interface, such as Adobe Photoshop. To accommodate complex operations with single- touch pointing devices, we must use widgets (such as a scroll bar or popup menu), modifier keys (such as control + click or double-click), or mouse actions (such as drag and drop). Although they’re usable, such traditional interfaces are less intuitive and impose a heavier cognitive load on the user. In contrast, multiple-touch technology has at- tracted much attention in recent years for its ease of use. A multiple-touch device can track more than one touch simultaneously, providing more sophis- ticated and intuitive interaction in user interface design. For example, to zoom into a photo using a multiple-touch interface, a user can first touch the photo with two fingers and then spread the fingers apart, as Figure 1a shows. The interface reacts as if the two fingers were stretching a printout on a rub- ber sheet. This pinching gesture is more intuitive and direct than using a slider widget for resizing in the traditional interface, as Figure 1b shows. Advances in multiple-touch hardware and user interface design have resulted in recent high-profile The Multiple-Touch User Interface Revolution 42 IT Pro January/February 2009 Published by the IEEE Computer Society 1520-9202/09/$25.00 © 2009 IEEE MULTIPLE-TOUCH TECHNOLOGY Authorized licensed use limited to: IEEE Xplore. Downloaded on February 3, 2009 at 04:42 from IEEE Xplore. Restrictions apply.