Liblouis User's and Programmer's Manual

2.15 Miscellaneous Opcodes ¶

include filename

Read the file indicated by filename and incorporate or include its entries into the table. Included files can include other files, which can include other files, etc. For an example, see what files are included by the entry include en-us-g1.ctb in the table en-us-g2.ctb. If the included file is not in the same directory as the main table, use a full path name for filename.

undefined dots

If this opcode is used in a table any characters which have not been handled in the table but are encountered in the text will be replaced by the dot pattern. If this opcode is not used, any undefined characters are replaced by '\xhhhh', where the h’s are hexadecimal digits.

display character dots

Associates dot patterns with the characters which will be sent to a braille embosser, display or screen font. The character must be in the range 0-255 and the dots must specify a single cell. Here are some examples:

# When the character a is sent to the embosser or display,
# it will produce a dot 1.
display a 1

# When the character L is sent to the display or embosser
# it will produce dots 1-2-3.
display L 123

The display opcode is optional. It is used when the embosser or display has a different mapping of characters to dot patterns than that given in Character-Definition Opcodes. If used, display entries must proceed character-definition entries.

A possible use case would be to define display opcodes so that the result is Unicode braille for use on a display and a second set of display opcodes (in a different file) to produce plain ASCII braille for use with an embosser.

multind dots opcode opcode ...

The multind opcode tells the back-translator that a sequence of braille cells represents more than one braille indicator. For example, in en-us-g2.ctb we have multind 56-6 letsign capsletter. The back-translator can generally handle single braille indicators, but it cannot apply them when they immediately follow each other. It recognizes the letter sign if it is followed by a letter and takes appropriate action. It also recognizes the capital sign if it is followed by a letter. But when there is a letter sign followed by a capital sign it fails to recognize the letter sign unless the sequence has been defined with multind. A multind entry may not contain a comment because liblouis would attempt to interpret it as an opcode.