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at encodings/README.md to match the recent folder rename by @graphicore
159 lines
5.6 KiB
Markdown
159 lines
5.6 KiB
Markdown
This directory contains "Namelist" files, that list Unicode characters followed by glyph names or glyph descriptions.
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Typically all the Unicodes in each file are in each font.
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If the fonts go beyond that list, those additional characters will not be available to Fonts API end users.
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The Google Fonts API uses these files in combination with [pyftsubset](https://github.com/behdad/fonttools/blob/master/Lib/fontTools/subset.py) to generate script subsets from the full `.ttf` files in this repository.
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There are "legacy" encodings, the files directly in this directory, and "novel" encodings contained in the `GF Glyph Sets` subdirectory.
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The latter directory contains itself a [`README.md`]('GF Glyph Sets/README.md').
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# The "Namelist" file format
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The extension of a Namelist file is "`.nam`".
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Namelist files are encoded in UTF-8.
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### *legacy* subsetting
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* all encodings with the exception of `khmer` include `latin_unique-glyphs.nam`
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* all *extended* encodings with filenames like`{lang}-ext_unique-glyphs.nam` also include `{lang}_unique-glyphs.nam`
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This is implemented in the `CodepointFiles` function of [google_fonts.py](../util/google_fonts.py)
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*NOTE: the legacy files have also been adapted to the novel header `#$ include` style.*
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### *novel* subsetting
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The [`README.md`]('GF Glyph Sets/README.md') describes mostly how each of the Namelist files depend on each other,
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to implement this [header includes](#header) were created.
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## Codepoint format
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A line that starts with `0x` and then have 4 or 5 **uppercase** hex digits; what follows is an arbitrary description to the end of the line.
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Example:
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```
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0x0061 a LATIN SMALL LETTER A
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0x0062 b LATIN SMALL LETTER B
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0x0063 c LATIN SMALL LETTER C
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0x03E4 Ϥ COPTIC CAPITAL LETTER FEI
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0x10142 𐅂 GREEK ACROPHONIC ATTIC ONE DRACHMA
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```
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## Comments
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Comments are lines starting with `#`.
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Example:
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```
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# Created by Alexei Vanyashin 2016-27-06
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#$ include ../GF-latin-plus_unique-glyphs.nam
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```
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## glyphs without Unicode (since the "novel" encodings)
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A line that starts with at least six spaces describes a glyph that has no Unicode and will usually be accessible via OpenType GSUB. These glyphs are used to ensure the fonts contain certain OpenType features.
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The description is a human readable glyph name that can be used in the authoring application (targeted at Glyphs) to create and process the glyph properly.
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Example:
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```
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aacute.sc
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abreve.sc
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abreveacute.sc
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abrevedotbelow.sc
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```
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For legacy reasons, we also accept lines in the form of:
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```
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Д uni0414.loclBGR
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И uni0418.loclBGR
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Й uni0419.loclBGR
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```
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Using this sample python implementation to obtain the glyph name:
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```py
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line.strip().rsplit(' ')[-1]
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```
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## <a name="header"></a> Header
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The header was created to make the Namelist format more self contained.
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The Namelist header is made of all consecutive comment lines at the beginning of the file. The first non-comment line ends the header.
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Specially crafted comment lines, "header data", define the meta data of the file. Other comments are just that, comments.
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A header data line begins with `#$` then is followed by a keyword and then followed by the arguments for the keyword.
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The keyword is separated from its arguments by one or more space characters.
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The keywords, the semantics of a keyword and the syntax of its arguments should be documented here.
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Format for header data:
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```
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#$ {keyword} {arguments}
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```
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### Keyword `#$ include {namfile}`
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The `include` keyword can be used zero or more times. Order of appearance should have no effect on the resulting set and thus be not important.
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It specifies the namfiles on which the current namfile depends. The file plus all of its includes together define the complete char-set.
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Includes are loaded recursively, meaning that the includes of an included files must also be loaded.
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E.g. a novel a "pro" encoding would include its "plus" encoding and the latter would include its "base" encoding. The Pro charset then is the union of pro, plus and base.
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Loops in the includes are not followed; the final result as a `set` wouldn't have a different value whether the same file is included once or many times.
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`{namfile}` is a file path to a namfile relative to the path of the file that contains the include statement.
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Example from `GF-latin-expert_unique-glyphs.nam`
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```
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#$ include GF-latin-pro_unique-glyphs.nam
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0x2153 ⅓ onethird
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0x2154 ⅔ twothirds
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0x215B ⅛ oneeighth
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```
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### Possible Keywords
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* `author {name}` (zero or more) since we can already find `# Created by` comments in the novel nam-files we could as well just institutionalize it.
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* `label {name}` A human readable name for the file, to be used in user interfaces. Could also have a further `{locale}` argument for internationalization.
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# Scripts
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A python script, `tools/namelist.py` can generate these files:
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namelist.py Font.ttf > NameList.nam
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The `[wgl-latin.enc]` file can be used by [Fontlab Studio 5](http://www.fontlab.com), and represented Microsoft's [Windows Glyph List 4](https://en.wikipedia.org/wiki/Windows_Glyph_List_4) glyph set.
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A python script, `tools/unicode_names.py` can reformat these files:
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python unicode_names.py --nam_file=encodings/latin_unique-glyphs.nam;
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0x0020 SPACE
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0x0021 ! EXCLAMATION MARK
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0x0022 " QUOTATION MARK
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0x0023 # NUMBER SIGN
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...
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Namelist parsing is implemented in:
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Python: `tools/util/google_fonts.py` use the function `CodepointsInSubset` for legacy Namelist files and `codepointsInNamelist` for novel Namelist files.
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JavaScript: [analyzeCharSets.js](https://github.com/graphicore/specimenTools/blob/languages/build/analyzeCharSets.js) implements novel style Namefile parsing.
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