Towards a Unified and Efficient Command Selection Mechanism for Touch-Based Devices Using Soft Keyboard Hotkeys

We advocate for the usage of hotkeys on touch-based devices by capitalising on soft keyboards through four studies. First, we evaluated visual designs and recommended icons with command names for novices while letters with command names for experts. Second, we investigated the discoverability by asking crowdworkers to use our prototype, with some tasks only doable upon successfully discovering the technique. Discovery rates were high regardless of conditions that vary the familiarity and saliency of modifier keys. However, familiarity with desktop hotkeys boosted discoverability. Our third study focused on how prior knowledge of hotkeys could be leveraged and resulted in a 5% selection time improvement and identified the role of spatial memory in retention. Finally, we compared our soft keyboard layout with a grid layout similar to FastTap. The latter offered a 12-16% gain on selection speed, but at a high cost in terms of screen estate and low spatial stability.