A graphics typesetting language

Abstract

We present a new programming language, IDEAL, in which two-dimensional figures can be expressed. The language is intended to work with existing text-formatting systems so that text and figures can be typeset at the same time. The building block for IDEAL programs is called a “box” it shares some features with procedures and some with records in general-purpose programming languages. A box includes a system of constraints (in this incarnation, equations in complex variables) that declares the relative positions of its significant points and requests for actions to be performed at those points. A box is called by adding enough constraints to the system in its definition that its significant points can be solved for uniquely. A box call may also include additional actions to be performed during the call. The notions of drawing a line using a pattern and texturing a polygonal area follow directly from the mechanism for defining and calling boxes. Users may also ask for a box to be “opaque” so that it blots out pieces of picture that it covers. Finally, two commands embody the idea of sketching several pictures on different parallel planes, then merging them into a single picture. We use these when erasing to create one part of a picture would destroy another part that we want. We discuss good algorithms for implementing IDEAL when the constraints are expressed as a special kind of nonlinear system and the pictures are composed of straight lines and circular arcs. The language has been implemented, and was used to produce the paper.