Efficient editing in a tree-oriented projectional editor

In contrast to text editors, using projectional editors typically requires users to learn a new editing metaphor. In text-oriented projectional editors, rules may be used to give users the impression of working in a regular text editor. As such, the editing metaphor appears clear to the user, but if the implemented rules do not suffice, users may be confused why certain actions do not work. Block-oriented projectional editors, where the editing metaphors are typically clearer, often present challenges in editing efficiency, as code takes up more space and editing is perceived to be slower. We present a block-oriented projectional editor that tries to address the issues of editing efficiency and space usage. Through a reusable set of commands for tree modifications, a space-efficient AST visualization, and context-aware input we allow users to edit as fast or faster than in a text editor. We provide a first evaluation by comparing the number of keystrokes required to carry out common edit operations.