BezelCursor: Bezel-Initiated Cursor for One-Handed Target Acquisition on Mobile Touch Screens

Introduction

It is reported that a user generally prefers one-handed interaction with a mobile touch device whenever possible (A.K. Karlson, Bederson, & Contreras-Vidal, 2007). That is, only a single hand is used to both hold and interact with the device (Figure 1 (left)). Unimanual interaction allows the user to operate the mobile device in a distracted, multitasking scenario and frees the other hand for tasks like carrying a bag, writing a relevant note etc. In such scenarios, the thumb of the hand holding the device is normally the only available finger for touch input (Boring et al., 2012; Hirotaka, 2003). However, mainly due to biomechanical limitations of the thumb, only a subregion of the touch screen is comfortable to access by the thumb (A. Karlson & Bederson, 2007) causing awkward hand postures to reach the rest of the screen (Figure 1 (right)). This problem of limited screen accessibility by the thumb deteriorates with screens of increasingly bigger sizes, which, however, are getting more and more popular (FINGAS, 2012).

Figure 1.

One-handed mobile interaction makes the thumb be the only finger for input and only a subregion of the screen, shown as the region with dashed line, is easily accessible with a comfortable grip of the device (left). Awkward hand postures to access the rest of the screen cause more fatigue, less precision, and unstable grip of the device (right).

Redesigning UIs tailored for one-handed interaction is certainly a possible solution but suffers from a few problems, e.g., causing additional constraints on interface design, sacrificing naturalness of direct manipulation. In contrast, designing new thumb interaction techniques which can be directly applied to existing UIs is more practical. Several one-handed target acquisition techniques such as ThumbSpace (A. Karlson & Bederson, 2007) and MagStick (Roudaut, Huot, & Lecolinet, 2008) have been proposed and allow the thumb to virtually access anywhere on a screen of moderate size. However, they are not compatible with commonly used interaction styles such as direct touch and dragging, forcing users to switch between input modes explicitly (Amy K. Karlson & Bederson, 2008), e.g., via selecting modes via buttons.

To address the above problems, we present BezelCursor, a new technique for one-handed target acquisition technique on mobile touch screens. Our solution is inspired by bezel-initiated interaction and pointing gesture. BezelCursor allows the user to select any object on the screen using a single fluid action, which is a seamless integration of bezel swiping for tool invocation and virtual pointing for target acquisition. More specifically, as illustrated in Figure 2, the user swipes with the thumb of the holding hand, from the outside of the physical bezel of the touch screen to the on-screen target in order to activate the BezelCursor. A visible cursor will be shown and pushed towards the target by the thumb's movement, similar to the use of the touch screen as a trackpad. The cursor will select the underneath element and disappear (deactivated) when the controlling thumb is lifted up.

Figure 2.

BezelCursor allows a user to easily access a target located anywhere on the screen, by combining bezel swipe for invocation (left) and pointing gesture for acquisition (right) into a single fluid action