| There exist several user interface widgets that grow or expand in response to the user's focus of attention. Some of these expand to facilitate their selection, allowing for a reduced initial size in an attempt to optimize screen space use. However, selection performance could plausibly suffer from a decreased initial widget size. We describe an experiment in which users select a single, isolated target button that expands just before it is selected. Our results suggest that users are able to take approximately full advantage of the expanded target size, even if the target only begins expanding after 90% of the movement towards the target has been completed. For interfaces with multiple expanding widgets, however, care must be taken to mitigate the collisions or overlap that may occur between adjacent widgets. We present a number of design strategies that attempt to optimize the performance of multiple, tiled expanding targets. |
