2D-Dragger: Unified Touch-based Target Acquisition with Constant Effective Width

18th International Conference on Human-Computer Interaction with Mobile Devices and Services

 (MobileHCI 2016)

Qingkun Su1      Oscar Kin-Chung Au2      Pengfei Xu3,1∗      Hongbo Fu2      Chiew-Lan Tai1

1Hong Kong University of Science and Technology      2City University of Hong Kong     3Shenzhen University

Figure 1. Overview of 2D-Dragger. Our technique uses a simple touch-and-drag operation to achieve efficient target acquisition. (a) When the user places a finger on the screen, a selectable target (if any) near the contact point within a small region of interest (gray circle) becomes the first captured target (solid black element 0). (b) Meanwhile a circular effective area (the left lighter green circle; slightly bigger for the firstly captured element) is defined at the captured element 0. The user can then capture a nearby target (element 1) by dragging the contact finger out from the effective area in the direction towards the new target. The right green circle is the effective area of element 1. (c) When a new target (element 2) is captured, a new circular effective area (the rightmost green circle) is placed at the current finger location. The user can then continuously capture the next nearby target by keep dragging the contact finger in the user’s intended direction. (d) Once the desired target is captured, the user can lift the contact finger to confirm the selection. The rightmost green circle represents the effective area of the current selection. Note that the green circles here are invisible to users.



In this work we introduce 2D-Dragger, a unified touch-based target acquisition technique that enables easy access to small targets in dense regions or distant targets on screens of various sizes. The effective width of a target is constant with our tool, allowing a fixed scale of finger movement for capturing a new target. Our tool is thus insensitive to the distribution and size of the selectable targets, and consistently works well for screens of different sizes, from mobile to wall-sized screens. Our user studies show that overall 2D-Dragger performs the best compared to the state-of-the-art techniques for selecting both near and distant targets of various sizes in different densities.



We thank all the reviewers of this paper for the insightful comments and constructive suggestions. This work was supported in parts by grants from Research Grants Council of HKSAR (16209514), City University of Hong Kong (7004298,7004498), NSFC (61232011), 973 Program (2015CB352501), Guangdong Science and Technology Program (2015A030312015, 2014B050502009) and Shenzhen Innovation Program (JCYJ20151015151249564).