An evaluation of integrated zooming and scrolling on small screens

Steve Jones, Matt Jones, Gary Marsden, Dynal Patel, Andy Cockburn
2005 International Journal of Human-Computer Studies  
Speed-dependent automatic zooming (SDAZ) has been proposed for standard desktop displays as a means of overcoming problems associated with the navigation of large information spaces. SDAZ combines zooming and panning facilities into a single operation, with the magnitude of both factors dependent on simple user interaction. Previous research indicated dramatic user performance improvements when using the technique for document and map tasks. In this paper we propose algorithmic extensions to
more » ... technique for application on small-screen devices and present a comparative experimental evaluation of user performance with the system and a normative scroll-zoom-pan interface. Users responded positively to the system, particularly in relation to reduced physical navigational workload. However, the reduced screen space reduced the impact of SDAZ in comparison to that reported in previous studies. In fact, for one-dimensional navigation (vertical document navigation) the normative interface out-performed SDAZ. For navigation in two dimensions (map browsing) SDAZ supports more accurate target location, but also produces longer task completion times. Some SDAZ users became lost within the information space and were unable to recover navigational context. We discuss the reasons for these observations and suggest ways in which limitations of SDAZ in the small-screen context may be overcome. Page 2 of 26 displayed. The subset shown within the viewport can be controlled by the user, who conceptually moves either the viewport around on top of the space, or the space around under the viewport. Scrollbars are a common control mechanism for this interaction, supporting both continuous and discrete (often in terms of pages) navigation actions, with one scrollbar providing vertical viewport control and another providing horizontal control. A further mechanism allows the user to drag the space within the viewport (often termed panning), manipulating its location directly in any direction without constraint to either horizontal or vertical movements. Another approach increases or decreases the size of the information space subset visible in the viewport via a zoom function. Although many systems provide all three of these scrolling, panning and zooming operations, there are numerous limitations to the navigation support that they provide. Igarashi and Hinckley (2000) note the attentional overhead incurred in changing focus between document content and scrollbars. Users must initially focus attention on a scrollbar to situate the cursor within the appropriate control item-usually one of two directional arrows, a scroll handle or either side of the scroll handle. During a scroll operation the user must then consider both the effect of the operation on the document and further possible actions in the scrollbar. Igarashi and Hinckley (2000) suggest that this can increase operational time. They also observe that small scrollbar movements can result in large movements of the viewport for long documents, causing disorientation and confusion for the user. Cockburn and Savage (2003) note that because zooming changes the visible proportion of the information space, more scrolling is required when zoomed in, and less when zoomed out to achieve the same transformation of the viewport. Given that scrolling operations are dependent upon the current zoom-level, scrollbars can have varying effects in response to the small set of available user actions. To predict, or interpret scrollbar interactions, users must therefore understand the relationship between scroll-distance and zoom-level, adding further overhead to scrolling operations.
doi:10.1016/j.ijhcs.2005.03.005 fatcat:lqq55ooxobaydddag3cls434oe