Improving Target Acquisitions through Utilizing Pen Pressure

Target selection via pointing is a fundamental task in graphical user interfaces (GUIs). A large corpus of work has been proposed to improve mouse-based pointing performance by manipulating control display (CD) parameters (Blanch et al., 2004; Grossman & Balakrishnan, 2005; Guiard et al., 2004; Kabbash & Buxton, 1995; Worden et al., 1997) in desktop environments. Compared with mouse-based desktop GUIs, pen-based interfaces have a number of different characteristics. First, pen-based interfaces typically use absolute pointing via a direct input device (i.e., a pen), which is very different from indirect input, such as using a mouse. Second, in addition to the 2D position (x, y) values, many pen-based devices offer additional sensory properties (such as pen pressure values) that can be useful for interaction. Third, many pen-based interfaces have limited display space and input footprint. As the amount of information displayed on the screen increases, users have to select smaller targets. This is especially obvious in mobile products, such as personal digital assistants (PDAs), pen-based mobile phones, and other mobile pen-based applications. Compared with the extensive studies carried out for mouse-based pointing, more empirical studies are needed to determine how we can improve pen-input usage and efficiency. Although previous studies have intended to exploit novel pen-based selection techniques, such as Slide Touch (Ren & Moriya, 2000), Drag-and-pop (Baudisch et al., 2003), Bubble Radar (Aliakseyeu et al., 2006) and Beam Cursor (Yin & Ren, 2006), these techniques were mostly designed for situations where targets are sparsely distributed across a display space. When targets are smaller and densely packed, the benefit of these techniques tends to be diminished or become unavailable.