Shadow Buttons: Exposing WIMP Functionality While Preserving the Inking Surface in Sketch-Based Interfaces

Abstract

We present Shadow Buttons, an approach to placing WIMP interface elements into gestural and sketch-based interfaces. Utilizing the hover state, supported by pen-based devices such as Tablet PCs, we provide users with important WIMP-based functionality by invoking widgets only when the stylus hovers over "shadow" regions. In this way, every pixel of the display, including the shadows, can be drawn on. By interacting with a shadow region while in the hover state, users can temporarily display and interact with familiar WIMP elements. We explore the Shadow Button design space as it relates to handwritten mathematical expressions and also present an informal evaluation of our technique, examining various Shadow Button parameters including button size, placement, and method of invocation. Preliminary results indicate that users prefer utilizing the hover state over tapping on the Shadow Button and in general, prefer interface elements to be as close to the ink as possible. In addition, the distance between the shadow region and the menu was found to be the most important factor in Shadow Button usability.