Hidden Messages: Evaluating the Effectiveness of Code Elision in Program Navigation

Text elision is a user interface technique that aims to improve the efficiency of navigating through information by allowing regions of text to be ‘folded’ into and out of the display. Several researchers have argued that elision interfaces are particularly suited to source code editing because they allow programmers to focus on relevant code regions while suppressing the display of irrelevant information. Elision features are now appearing in commercial systems for software development. There is, however, a lack of empirical evidence of the technique’s effectiveness. This paper presents an empirical evaluation of source code elision using a Java program editor. The evaluation compared a normal ‘flat text’ editor with two versions that diminished elided text to levels that were ‘just legible’ and ‘illegible’. Subject performance was recorded in four tasks involving navigation through programs. Results show that programmers were able to complete their tasks more rapidly when using the elision interfaces, particularly in larger program files. Although the subjects indicated a preference for the ‘just legible’ elision interface, their performance was best with illegible elision.