DownChord and UpChord: A New Style of Keyboard Shortcuts based on Simultaneous Key-down and Key-up Events

Typical typing, as well as many other keyboard operations including using modifier-based shortcuts, is dependent upon the order of key press and avoids simultaneous key pressing. This paper introduces DownChord and UpChord, novel keyboard shortcut techniques, which utilizes the simultaneous key pressing and releasing for defining new classes of shortcuts. Our technique can be used on ordinary unmodified physical keyboard seamlessly -- without interfering major functionality of computer keyboard such as typing and activation of existing modifier-based shortcuts. We conducted controlled experiments to determine the appropriate time thresholds for detecting shortcuts from the input keyboard event queue, which allows our shortcuts to be activated effortlessly with only average latency of 160 ms. Results of our user study show that DownChord and UpChord are promising shortcut techniques which gives competitive performance as existing modifier-base shortcuts.