Display procedures

Although the use of structured display files is widespread in interactive computer graphics, these structures present a number of problems which tend to restrict their generality and usefulness. This paper discusses some of these problems, and suggests an alternative approach to display system design which avoids the use of structured display files. This technique employs display procedures to generate information for display. By including transformations within calls to these procedures it is possible both to simplify the specification of pictures and to speed up their generation. Display procedures permit picture elements to be defined conditionally and also facilitate the processing of inputs from pointing devices. The paper is illustrated by examples from a version of the EULER language in which display procedures were implemented.

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