Selections and actions in GUI's are often separated ? i.e. an action or command typically follows a selection. This sequence imposes a lower bound on the interaction time that is equal to or greater than the sum of its parts. In this paper, we introduce pressure marks ? pen strokes where the variations in pressure make it possible to indicate both a selection and an action simultaneously. We propose a series of design guidelines from which we develop a set of four basic types of pressure marks. We first assess the viability of this set through an exploratory study that looks at the way users draw straight and lasso pressure marks of different sizes and orientations. We then present the results of a quantitative experiment that shows that users perform faster selection-action interactions with pressure marks than with a combination of lassos and pigtails. Based on these results, we present and discuss a number of interaction designs that incorporate pressure marks. ACM Classificat...
Gonzalo A. Ramos, Ravin Balakrishnan