The function takes three arguments. The second is the outline point number at the top of the base glyph. The third is the bottom outline point number of the diacritic. The contours are numbered starting at zero. Languages based on the Latin alphabet.
Examples are English, French, German, Spanish and Italian.
Glyphs are given numbers starting at zero. The numbers are used by tables and instructions to access the glyphs. TrueType fonts use a 2048 Unit Per EM measurement system. In comparison PostScript uses a 1000 unit system. A series of curves and straight lines that are filled with pixels to make an image.