samsa-core need to set substituteGlyphId when there is glyph change along the axis

[Typogram]

Samsa-core requires substitute glyph to be set manually when there is a glyph changes along the axis:

if (font.featureVariations) {
  let substituteGlyphId = glyph.featureVariationsGlyphId(
    preset.tuple
  );
  if (substituteGlyphId !== undefined) {
    tempGlyph = font.glyphs[substituteGlyphId];
  }
}
let pathData = tempGlyph.decompose(preset.tuple).svgPath();

Gif: fontkit and harfbuzz have the correct rendering

[Lorp]

That’s a good point. Feature variations are not yet implemented in Samsa Core 2, although they do work in Samsa GUI tool. I’ll get to it. It’s curious that this glyph does not work at all in the system rendering. Do you know why that might be?

[Typogram]

Wow, cool! you are working on Samsa Core 2, what is it? Is it the Typescript port of the original Samsa-core? Will it have new functionalities and api?

I don't know why it doesn't work on system, maybe there is some kind of name conflict or font face issue? I assume it is not a font issue because it renders on https://wakamaifondue.com/

[Lorp]

RenderStack already uses Samsa Core 2. It’s not complete yet, as you’ve demostrated, but it’s pretty much a rewrite from scratch of the Samsa Core over on the Samsa GUI repo. The decision to switch to Typescript is basically taken, but that won’t be ready for some time.

If you can send me the font, I may be able to check it out when I have some time.

[Typogram]

I am not too worried about the system not working. So no need to check it! Thanks for offering!