Wavelet menus on handheld devices: Stacking metaphor for novice mode and eyes-free selection for expert mode

This paper presents the design and evaluation of the Wavelet menu and its implementation on the iPhone. The Wavelet menu consists of a concentric hierarchical Marking menu using simple gestures. The novice mode, i.e. when the menu is displayed, is well adapted to the limited screen space of handheld devices because the representation of the menu hierarchy is inverted, the deeper submenu being always displayed at the center of the screen. The visual design is based on a stacking metaphor to reinforce the perception of the hierarchy and to help users to quickly understand how the technique works. The menu also supports submenu previsualization, a key property to navigate efficiently in a hierarchy of commands. The quantitative evaluation shows that the Wavelet menu provides an intuitive way for supporting efficient gesture-based navigation. The expert mode, i.e. gesture without waiting for the menu to pop-up, is another key property of the Wavelet menu: By providing stroke shortcuts, the Wavelet favors the selection of frequent commands in expert mode and makes eyes-free selection possible. A user experiment shows that participants are able to select commands, eyes-free, while walking.