Projection Boxes: On-the-fly Reconfigurable Visualization for Live Programming

Live programming is a regime in which the programming environment provides continual feedback, most often in the form of runtime values. In this paper, we present Projection Boxes, a novel visualization technique for displaying runtime values of programs. The key idea behind projection boxes is to start with a full semantics of the program, and then use projections to pick a subset of the semantics to display. By varying the projection used, projection boxes can encode both previously known visualization techniques, and also new ones. As such, projection boxes provide an expressive and configurable framework for displaying runtime information. Through a user study we demonstrate that (1) users find projection boxes and their configurability useful (2) users are not distracted by the always-on visualization (3) a key driving force behind the need for a configurable visualization for live programming lies with the wide variation in programmer preferences.