This directory includes auxiliary information that is either tangential to the main shaping-behavior documentation or is excessively long enough that trying to include it inline would disrupt the flow of the text for readers.
Notes included cover:
- Uniscribe compatibility: Information on preserving strict compatibility with Microsoft's Uniscribe shaping engine
- Ragel state-machine operators: Information on the syntax of the Ragel state-machine compiler, which is the reference regular-expression syntax used when listing regular expressions in the shaping-behavior documentation, but which itself is not mandatory.
- Emoji implementation: Information on the image formats, codepoint visibility, and GSUB/GPOS features used in real-world Emoji fonts distributed by major vendors.