Evaluate FeatureVariations at the default location

src/opentype/OTProcessor.js

@@ -17,9 +17,19 @@ export default class OTProcessor {
     this.features = {};
     this.lookups = {};
 
-    // Setup variation substitutions
-    this.variationsIndex = font._variationProcessor
-      ? this.findVariationsIndex(font._variationProcessor.normalizedCoords)
+    // Setup variation substitutions. FeatureVariations apply at the font's
+    // current location, defaulting to the normalized origin (all-zero coords)
+    // when no variation is set — matching HarfBuzz, which always evaluates them.
+    // fontkit only builds a _variationProcessor once coords are applied (or for
+    // CFF2), so a plain variable font would otherwise skip FeatureVariations
+    // (e.g. default-location bracket-layer substitutions) entirely.
+    let variationCoords = font._variationProcessor
+      ? font._variationProcessor.normalizedCoords
+      : font.fvar
+        ? new Array(font.fvar.axis.length).fill(0)
+        : null;
+    this.variationsIndex = variationCoords
+      ? this.findVariationsIndex(variationCoords)
       : -1;
 
     // initialize to default script + language

test/data/fonttest/TestFeatureVariations.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+# Generates TestFeatureVariations.ttf: a minimal TTF variable font whose `rvrn`
+# FeatureVariations substitutes A -> A.alt under a condition set that covers the
+# default location (normalized wght in [0, 1], which includes the default 0).
+# Used to test that fontkit evaluates FeatureVariations at the default location.
+# Build: python3 TestFeatureVariations.py TestFeatureVariations.ttf
+import sys
+from fontTools.fontBuilder import FontBuilder
+from fontTools.varLib.featureVars import addFeatureVariations
+from fontTools.pens.ttGlyphPen import TTGlyphPen
+
+
+def box(x0, y0, x1, y1):
+    pen = TTGlyphPen(None)
+    pen.moveTo((x0, y0)); pen.lineTo((x0, y1))
+    pen.lineTo((x1, y1)); pen.lineTo((x1, y0)); pen.closePath()
+    return pen.glyph()
+
+
+glyphs = ['.notdef', 'A', 'A.alt']
+fb = FontBuilder(1000, isTTF=True)
+fb.setupGlyphOrder(glyphs)
+fb.setupCharacterMap({0x41: 'A'})
+fb.setupGlyf({'.notdef': box(0, 0, 0, 0), 'A': box(100, 0, 500, 700),
+              'A.alt': box(100, 0, 400, 700)})
+fb.setupHorizontalMetrics({g: (600, 100) for g in glyphs})
+fb.setupHorizontalHeader(ascent=800, descent=-200)
+fb.setupNameTable({'familyName': 'TestFeatureVariations', 'styleName': 'Regular'})
+fb.setupOS2(); fb.setupPost()
+fb.setupFvar(axes=[('wght', 0, 400, 1000, 'Weight')], instances=[])
+fb.setupGvar({})
+addFeatureVariations(fb.font, [([{'wght': (0, 1)}], {'A': 'A.alt'})], featureTag='rvrn')
+fb.save(sys.argv[1])

test/shaping.js

@@ -582,4 +582,15 @@ describe('shaping', function () {
       test('SHBALI-2/12', 'NotoSans/NotoSansBalinese-Regular.ttf', "ᬓ᭄ᭅᬸ", '23+2275|162+0|60@0,-1000+0');
     });
   });
+
+  describe('FeatureVariations', function () {
+    it('applies FeatureVariations at the default variation location', function () {
+      // TestFeatureVariations.ttf's rvrn feature substitutes A -> A.alt under a
+      // condition set covering the default location. HarfBuzz applies it; so
+      // must fontkit, even with no explicit variation instance selected.
+      let font = fontkit.openSync(new URL('data/fonttest/TestFeatureVariations.ttf', import.meta.url));
+      let { glyphs } = font.layout('A');
+      assert.deepEqual(glyphs.map(g => g.name), ['A.alt']);
+    });
+  });
 });