Making structured graphics and constraints practical for large-scale applications

Providing a structured graphics model and a constraint system makes the programming of graphical applications significantly easier. In a structured graphics model, each graphic element on the screen is represented by a real object in the object system, while a constraint system automatically maintains relationships among the objects. Although many research systems and a few commercial environments provide structured graphics and constraints, none scale up to large interfaces with thousands of objects and thousands of constraints. This paper presents four techniques to overcome this problem: automatic elimination of constraints that depend only on values that do not change, layout hints to help with refresh and hit detection, "virtual aggregates " that only pretend to allocate objects for their components, and compiling composite aggregates into a single object with a complex draw method. These have been implemented as part of the Garnet environment, and we have demonstrated that together they allow structured graphics and constraints to scale up to applications with tens of thousands of objects and constraints without compromising the ease-of-use