> The next thing I'm doing for the adjustment database is making > combining characters work. Currently, only precomposed characters > will be adjusted. If my understanding is correct, this would mean > finding any lookups that map a character + combining character onto > a glyph, then apply the appropriate adjustments to that glyph.
Yes. I suggest that you use the `ttx` decompiler from fonttools and analyse the contents of a GSUB table of your favourite font. https://pypi.org/project/fonttools/ At the same time, use the `ftview` FreeType demo program with an appropriate `FT2_DEBUG` setting so that you can see what the current HarfBuzz code does for the given font. Examples: ``` ttx -t GSUB arial.ttf FT2_DEBUG="afshaper:7 afglobal:7 -v" \ ftview -l 2 -kq arial.ttf &> arial.log ``` Option `-l 2` selects 'light' hinting (i.e., auto-hinting), `-kq` emulates the 'q' keypress (i.e., quitting immediately). See appended files for `arial.ttf` version 7.00. In `arial.log`, the information coming from the 'afshaper' component tells you the affected GSUB lookups; this helps poking around in the XML data as produced by `ttx`. The 'afglobal' information tells you the glyph indices covering a given script and feature (start with 'latn_dflt'). You might also try a font editor of your choice (for example, FontForge, menu entry 'View->Show ATT') to further analyze how the GSUB data is constructed, and to get some visual feeling on what's going on. > Right now, I'm trying to figure out what features I need to look > inside to find these lookups. Should I just search all features? Yes, I think so. Since the auto-hinter is agnostic to the script and the used language, you have to have all information in advance. > After that, I'm going to tackle the tilde-flattening issue, and any > other similar marks that are getting flattened. Note that in most fonts you won't find any GSUB data for common combinations like 'a' + 'acute' -> 'aacute'. Usually, such stuff gets handled by the GPOS table, i.e., instead of mapping two glyphs to a another single one, the accent gets moved to a better position. In this case, the glyphs are rendered separately, *outside of FreeType's scope*. This means that we can't do anything on the auto-hinter side to optimize the distance between the base and the accent glyph (see also the comment in file `afshaper.c` starting at line 308, and this nice article https://learn.microsoft.com/en-us/typography/develop/processing-part1). It thus probably makes sense to do the tilde stuff first. Werner
arial-7.00.ttx.xz
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arial-7.00.log.xz
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