Comment by zerocrates

1 year ago

A new experimental feature of HarfBuzz allows the font to include WASM code for the shaper within the font itself. So the code shown in the post is inside the font and getting run "live," rather than being something that generated or modified the ligature tables in the font file in advance.

I wondered myself about just using "simple" ligatures, but I don't know whether or not it's feasible to statically store several thousand ligature definitions in a font that are each mostly runs of several thousand characters being substituted. But maybe? OpenType has mysterious depths.

4 comments

zerocrates

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jansan  1 year ago

Should be no problem. GSUB lookup type 4.1* uses a uint16 to store the number of ligatures, so 65000 ligatures should be feasible. To store the actual glyphs, 32bit offsets are used, so you theoretically have a 2GByte of memory available, which should be plenty (although I have never seen a font larger than 15MB).

Using Wasm for this animation really is an overkill IMHO.

*) https://learn.microsoft.com/en-us/typography/opentype/spec/g...

Edit: IIRC Ligatures are applied recursively, so you can have a ligature based on other ligatures. If I am right here, each ligature can consist only of two glyphs (the glyph of the previous animation frame followed by a dot). This would keep the GSUB table small.

  • erk__  1 year ago

    I used wasm because bad apple was the first thing I thought of when I saw the update that added wasm. I have thought about doing something where wasm fits better, but I have not gotten around to that yet.