Visual design for a tree-oriented projectional editor

Abstract

Projectional editors show promise for a variety of use cases, for example in language composition and domain specific projections. To allow efficient interactions within a projectional editor, it is necessary for the editor to clearly communicate the structure of the program to the user, such that it is clear what editing operations are supported for a given element. Making the abstract syntax tree visible within the editor may provide this clarity, however, it generally also results in considerably increased space usage, potentially also impacting usability. We present an early prototype of a tree-oriented projectional editor for Squeak/Smalltalk that tries to minimize space usage while retaining a clear visualization of the tree structure, balancing the two problems. We describe and discuss our design prototype and do a preliminary evaluation through individual account of experience working with the editor on various projects.