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AutoCAD font and shape files (SHX) are compiled from shape definition files (SHP). You can create or modify shape definition files with a text editor or word processor that saves files in ASCII format.
The syntax of the shape description for each shape or character is the same regardless of the final use (shape or font) for that shape description. If a shape definition file is to be used as a font file, the first entry in the file describes the font itself rather than a shape within the file. If this initial entry describes a shape, the file is used as a shape file.
Being able to create your own shape definitions is a valuable skill. Keep in mind, however, that this is a very complex subject to learn and requires patience.
Each line in a shape definition file can contain up to 128 characters. Longer lines cannot be compiled. Because AutoCAD ignores blank lines and text to the right of a semicolon, you can embed comments in shape definition files.
Each shape description has a header line of the following form and is followed by one or more lines containing specification bytes, separated by commas and terminated by a 0.
*shapenumber,defbytes,shapename
specbyte1,specbyte2,specbyte3,...,0
The following list describes the fields of a shape description:
- shapenumber
-
A number, unique to the file, between 1 and 258 (and up to 32768 for Unicode fonts), and preceded by an asterisk (*). Non-Unicode font files use the shape numbers 256, 257, and 258 for the symbolic identifiers Degree_Sign, Plus_Or_Minus_Sign, and Diameter_Symbol. For Unicode fonts these glyphs appear at the U+00B0, U+00B1, and U+2205 shape numbers and are part of the “Latin Extended-A” subset.
Text fonts (files containing shape definitions for each character) require specific numbers corresponding to the value of each character in the ASCII code; other shapes can be assigned any numbers.
- defbytes
- shapename
- specbyte
-
A shape specification byte. Each specification byte is a code that defines either a vector length and direction or one of a number of special codes. A specification byte can be expressed in the shape definition file as either a decimal or hexadecimal value. This section uses both decimal and hexadecimal specification byte values for its examples (as do many of the shape definition files). If the first character of a specification byte is a 0 (zero), the two characters that follow are interpreted as hexadecimal values.