Pointing on large displays with an indirect, relative pointing device such as a touchpad often requires clutching. This article introduces gliding, where the cursor continues to move during the clutching gestures. The effect is that of controlling the cursor as a detached object that can be pushed, with inertia and friction similar to a puck being pushed on a table. We analyze gliding from a practical and a theoretical perspective and report on two studies. The first controlled experiment establishes that gliding reduces clutching and can improve pointing performance for large distances. We introduce cursor efficiency to capture the effects of gliding on clutching. The second experiment demonstrates that participants use gliding even when an efficient acceleration function lets them perform the task without it, without degrading performance.

Touchscreen interaction currently relies on a limited set of multi-touch gestures and a wide range of graphical widgets that are often difficult to manipulate and consume much screen real-estate. Many tasks remain tedious to perform on touchscreens: selecting text over multiple views, manipulating different degrees of freedom of a graphical object, invoking a command and setting its parameter values in a row. We propose a design space of simple multi-touch gestures that designers of user interfaces can systematically explore to propose more gestures to users. We further consider a set of 32 gestures for tablet-sized devices, by proposing an incremental recognition engine that works with current hardware technology, and empirically testing the usability of those gestures. In our experiment, individual gestures are recognized with an average accuracy of ~90%, and users successfully achieve some of the transitions between gestures without the use of explicit delimiters. The goal of our contribution is to assist designers in optimizing the use of the rich multi-touch input channel for the activation of discrete and continuous controls, and enable fluid transitions between controls.

Substantial amount of research in Psychology has studied how people manipulate objects in the physical world. This work has unveiled that people show strong signs of prospective motor planning, i.e., they choose initial grasps that avoid uncomfortable end postures and facilitate object manipulation. Interactive tabletops allow their users great flexibility in the manipulation of virtual objects but to our knowledge previous work has never examined whether prospective motor control takes place in this context. To test this, we ran three experiments. We systematically studied how users adapt their grasp when asked to translate and rotate virtual objects on a multitouch tabletop. Our results demonstrate that target position and orientation significantly affect the orientation of finger placement on the object. We analyze our results in the light of the most recent model of planning for manipulating physical objects and identify their implications for the design of tabletop interfaces. \

The widely-held view that Fitts' law expresses a speed/accuracy trade-off is presumably correct, but it is vague. We outline a simple resource-allocation theory of Fitts' law in which movement time and error trade for each other. The theory accounts quite accurately for the data of Fitts' (1954) seminal study, as well as some fresh data of our own. In both data sets we found the time/error trade-off to obey a power law. Our data, which we could analyze more thoroughly than Fitts', are consistent with a square-root function with a single adjustable constant. We suggest that the resource-allocation framework should help combine information and energy considerations to allow a more complete account of Fitts' law.