# Notes #

This section 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](/notes/uniscribe-bug-compatibility.md):
    Information on preserving strict compatibility with Microsoft's
    Uniscribe shaping engine
  - [Ragel state-machine operators](/notes/ragel-machine-notation.md):
    Information on the syntax of the
    [Ragel](http://www.colm.net/open-source/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](/notes/emoji-implementation.md): Information
    on the image formats, codepoint visibility, and <abbr title="Glyph Substitution table">GSUB</abbr>/<abbr title="Glyph Positioning table">GPOS</abbr> features
    used in real-world Emoji fonts distributed by major vendors.