Fix logic in handling of an empty private points list in gvar

README.md

@@ -206,7 +206,7 @@ Options is an optional _{GlyphRenderOptions}_ object containing:
 * `language`: language system used to determine which features to apply (default: `"dflt"`)
 * `kerning`: if true takes kerning information into account (default: `true`)
 * `features`: an object with [OpenType feature tags](https://docs.microsoft.com/en-us/typography/opentype/spec/featuretags) as keys, and a boolean value to enable each feature.
-Currently only ligature features `"liga"` and `"rlig"` are supported (default: `true`).
+Currently only ligature features `"liga"`, `"rlig"` and `"calt"`  are supported (default: `true`).
 * `hinting`: if true uses TrueType font hinting if available (default: `false`).
 * `colorFormat`: the format colors are converted to for rendering (default: `"hexa"`). Can be `"rgb"`/`"rgba"` for `rgb()`/`rgba()` output, `"hex"`/`"hexa"` for 6/8 digit hex colors, or `"hsl"`/`"hsla"` for `hsl()`/`hsla()` output. `"bgra"` outputs an object with r, g, b, a keys (r/g/b from 0-255, a from 0-1). `"raw"` outputs an integer as used in the CPAL table.
 * `fill`: font color, the color used to render each glyph (default: `"black"`)

docs/index.html

@@ -36,6 +36,7 @@ <h1><a href="./">opentype.js</a></h1>
     <label><input type="checkbox" name="drawMetrics">Draw Metrics</label>
     <label><input type="checkbox" name="kerning" checked="checked">Kerning</label>
     <label><input type="checkbox" name="ligatures" checked="checked">Ligatures</label>
+    <label><input type="checkbox" name="contextualAlternates" checked="checked">Contextual Alternates</label>
     <label class="disabled"><input name="hinting" type="checkbox" disabled="true">Hinting</label>
 
     <div id="variation-options"></div>
@@ -145,7 +146,8 @@ <h1>Free Software</h1>
         hinting: form.hinting.checked,
         features: {
             liga: form.ligatures.checked,
-            rlig: form.ligatures.checked
+            rlig: form.ligatures.checked,
+            calt: form.contextualAlternates.checked
         }
     };
     window.fontOptions = Object.assign({}, window.font.defaultRenderOptions, window.fontOptions, options);

src/bidi.mjs

@@ -13,6 +13,7 @@ import ccmpReplacementCheck from './features/ccmp/contextCheck/ccmpReplacement.m
 import ccmpReplacement from './features/ccmp/ccmpReplacementLigatures.mjs';
 import latinWordCheck from './features/latn/contextCheck/latinWord.mjs';
 import latinLigature from './features/latn/latinLigatures.mjs';
+import latinContextualAlternates from './features/latn/latinContextualAlternates.mjs';
 import thaiWordCheck from './features/thai/contextCheck/thaiWord.mjs';
 import thaiGlyphComposition from './features/thai/thaiGlyphComposition.mjs';
 import thaiLigatures from './features/thai/thaiLigatures.mjs';
@@ -202,6 +203,16 @@ function applyLatinLigatures() {
     }
 }
 
+function applyLatinContextualAlternates() {
+    if (!this.hasFeatureEnabled('latn', 'calt')) return;
+    checkGlyphIndexStatus.call(this);
+    const ranges = this.tokenizer.getContextRanges('latinWord');
+    for (let i = 0; i < ranges.length; i++) {
+        const range = ranges[i];
+        latinContextualAlternates.call(this, range);
+    }
+}
+
 function applyUnicodeVariationSequences() {
     const ranges = this.tokenizer.getContextRanges('unicodeVariationSequence');
     for(let i = 0; i < ranges.length; i++) {
@@ -248,6 +259,7 @@ Bidi.prototype.applyFeaturesToContexts = function () {
     }
     if (this.checkContextReady('latinWord')) {
         applyLatinLigatures.call(this);
+        applyLatinContextualAlternates.call(this);
     }
     if (this.checkContextReady('arabicSentence')) {
         reverseArabicSentences.call(this);
@@ -303,7 +315,11 @@ Bidi.prototype.getTextGlyphs = function (text) {
         const token = this.tokenizer.tokens[i];
         if (token.state.deleted) continue;
         const index = token.activeState.value;
-        indexes.push(Array.isArray(index) ? index[0] : index);
+        if (Array.isArray(index)) {
+            for (const g of index) indexes.push(g);
+        } else {
+            indexes.push(index);
+        }
     }
     return indexes;
 };

src/features/applySubstitution.mjs

@@ -20,6 +20,16 @@ function singleSubstitutionFormat2(action, tokens, index) {
     tokens[index].setState(action.tag, action.substitution);
 }
 
+/**
+ * Apply multiple substitution format 1 (one glyph → sequence of glyphs).
+ * The full sequence is stored on the token; getTextGlyphs expands it into
+ * separate glyph indices, and latinContextualAlternates uses only the first
+ * element for context matching in subsequent lookups.
+ */
+function multipleSubstitutionFormat1(action, tokens, index) {
+    tokens[index].setState(action.tag, action.substitution);
+}
+
 /**
  * Apply chaining context substitution format 3
  * @param {Array} substitutions substitutions
@@ -32,8 +42,9 @@ function chainingSubstitutionFormat3(action, tokens, index) {
         const token = tokens[index + i];
         if (Array.isArray(subst)) {
             if (subst.length){
-                // TODO: replace one glyph with multiple glyphs
-                token.setState(action.tag, subst[0]);
+                // Store the full multi-glyph sequence on the token so all
+                // fragment glyphs reach the output stream via getTextGlyphs.
+                token.setState(action.tag, subst);
             } else {
                 token.setState('deleted', true);
             }
@@ -65,9 +76,13 @@ function ligatureSubstitutionFormat1(action, tokens, index) {
 const SUBSTITUTIONS = {
     11: singleSubstitutionFormat1,
     12: singleSubstitutionFormat2,
+    21: multipleSubstitutionFormat1,
+    61: chainingSubstitutionFormat3,
+    62: chainingSubstitutionFormat3,
     63: chainingSubstitutionFormat3,
     41: ligatureSubstitutionFormat1,
     51: chainingSubstitutionFormat3,
+    52: chainingSubstitutionFormat3,
     53: chainingSubstitutionFormat3
 };