Skylines: Visualizing Object-Oriented Software Systems Through Class Contours

Classes are the fundamental building blocks of object-oriented software systems, making their comprehension critical for effective software maintenance and evolution. Traditional source code views provide detailed information but often lack intuitive representations that reveal the structural and behavioral roles of a class at a glance. This is even harder for an overview of multiple classes in large and complex codebases. Moreover, identifying patterns and anomalies within classes remains challenging through conventional inspection.We propose Class Contours, a novel visualization metaphor that portrays individual classes as simple 2D architectural structures. Our approach visually encodes key class properties (e.g., lines of code, attributes, accessors) into customizable building features (e.g., windows, door frames, doors), supporting pattern recognition and task-specific visual exploration. With ZION, the tool we developed to exemplify our approach, we investigate how common class types correspond to recurring visual archetypes, allowing developers to swiftly recognize typical roles and structures within software systems.Our initial findings suggest that the simple but effective metaphor can enhance the understanding of class semantics in large codebases and support the identification of design issues and code smells.