US Patent 7783969 Rule-based text layout

The invention features systems, methods, and computer program products for typesetting a sequence of character glyphs. In on implementation, the invention provides a spacing classification file for a character set, the classification file being a text file, containing text form definitions of multiple character classes, each character class definition being structured to define a character class as having one or more arbitrary characters, the classification file further containing, in text form, multiple inter-class spacing definitions, each inter-class spacing definition defining, for an order pair of character classes, one or more spacing parameters for the ordered pair and an associated priority for each defined spacing parameter. A line of text can be compressed or expanded according to the inter-class spacing definitions for each sequential pairs of characters in the sequence of characters defined in the classification file according to their respective priorities.