DLI Implementation and Reference Guide - Datalogics

Displaying Line Drawings 10.3.
Approaches to Line Drawing
There are two approaches to line drawing supported by DLI. The first uses a simple
interface to construct or fill and stroke a structure. The second permits the user to
construct an arbitrarily complex collection of markings, and then place that collection
within any number of content structures.
Directly-Drawn Methods
In general, the directly-drawn methods are the simplest to use, and the best choice for
operations like underlining, page rules and area borders. This collection of directlydrawn
structures is derived from the operators for PostScript graphics, and common
usage of those operators.
All of these operators have their first three parameters in common. These are:
• The container in which the structure will be drawn
• The current state in which all parameters are used
• The Painting operator, which defines how the path defined should be treated. It
must be one of the following, or a combination of these:
• kPDEStroke — stroke the lines of the structures
• kPDEFill — fill the areas defined by the lines
• kPDEEOFill — stroke the area contained an odd number of times by the
area.
In the case of these structures, there can be no multiple containment, and hence
EOFill and Fill will have the same results.
All of the methods have additional parameters, specifying the location and size of the
structure drawn. These will be different for each structure, but will always be
ASFixed values.
If the content area in which these structures are drawn is itself distorted (i.e. its
AreaMatrix is not the unity matrix; see the discussion of containers and matrix
manipulation beginning with “What are Containers?” on page 7.2), then the
structures drawn will be positioned and shaped to reflect that distortion.