[lehni]

Problem

A variable font with no explicit variation set builds no _variationProcessor (the non-CFF2 path returns null when no coords are applied), so OTProcessor skips FeatureVariations entirely — unlike HarfBuzz, which always evaluates them at the current location. As a result, default-location substitutions (e.g. bracket-layer / rvrn alternates whose condition set covers the default) never apply unless you explicitly instance the font.

Fix

Evaluate FeatureVariations at the normalized origin (all-zero coords) for a variable font that has no _variationProcessor, so default-location substitutions apply — matching HarfBuzz.

Tests

Adds a small subset of Archivo (OFL) as a fixture: its rvrn swaps $/¢ for bracket-layer alternates from wght 500 up, which covers the default (600). Without the fix the test yields dollar/cent; with it, dollar.BRACKET.110/cent.BRACKET.110, matching HarfBuzz.

[blikblum]

Adds a minimal generated TTF variable-font fixture

This issue can be replicated with a non synthetic font?

[lehni]

Yes, it shows up in one of our not yet released commercial fonts, Unica77 LL Var (cousin of https://lineto.com/typefaces/unica77)

At the default location HarfBuzz substitutes 1 → one.BRACKET.varAlt01 through FeatureVariations, while fontkit kept one. We can't add that font to the repo, but it also reproduces with Archivo (OFL): its rvrn swaps $/¢ for bracket-layer alternates from wght 500 up, which covers the default (600). I'm going to replace the synthetic fixture with a small Archivo subset.