BubbleBoard: A Zoom-Based Text Entry Method on Smartwatches

We present a novel text entry method for smartwatches named BubbleBoard. It is based on a soft keyboard with a QWERTY layout in which some characters are in a big font and can be entered with a single touch, while other characters are in a small font and a touch enlarges the pressed character and its neighbors, so that they can be entered with a second touch. Different variants of the method, regarding the use of a static or dynamic layout and the input of space/backspace with keys or gestures were evaluated through a user study, with the one with a dynamic layout and space/backspace keys resulting as the fastest. This variant was then compared to ZoomBoard, an existing text entry method for smartwatches based on key magnification. The experiment showed a 33% advantage in text entry speed in favor of BubbleBoard. In particular, participants typed at 10.7 wpm with BubbleBoard and at 8.0 wpm with ZoomBoard.