leave generated .notdef glyph unmapped in cmap #428
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https://learn.microsoft.com/en-us/typography/opentype/spec/cmap#overview 'Regardless of the encoding scheme, character codes that do not correspond to any glyph in the font should be mapped to glyph index 0. The glyph at this location must be a special glyph representing a missing character, commonly known as .notdef.'
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FWIW, I verified with ttx_diff.py that Oswald's cmap is unchanged and matches fontmake even after this PR. |
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.notdef glyph represent the absence of a character, so it should not be explicitly mapped in the cmap. Currently we were adding a no-op map from 0x0000 (the NULL character) to glyph index 0 (.notdef) but this is unnecessary.
https://learn.microsoft.com/en-us/typography/opentype/spec/cmap#overview
NULL is for something else entirely. Basically all character codepoints that are not suppoted in a given font (including NULL in the particular case of the test font as well as most font nowadays) get implicitly mapped to glyph id 0, aka ".notdef" glyph.