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GSUB lookup table type 7 subtable format 1 #486

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merged 3 commits into from
Feb 26, 2023
Merged

GSUB lookup table type 7 subtable format 1 #486

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4b70c83
Support lookup table type 7 format 1 (Extension substitution subtable…
st0nerhat Aug 12, 2021
4ad01dc
Run lookup after translating extension subtable
st0nerhat Aug 12, 2021
18699e6
added test for lookup7 subtable format 1 parsing (#2)
Connum Feb 13, 2023
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34 changes: 28 additions & 6 deletions src/features/featureQuery.js
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Original file line number Diff line number Diff line change
Expand Up @@ -149,15 +149,27 @@ function chainingSubstitutionFormat3(contextParams, subtable) {
const lookupListIndex = lookupRecord.lookupListIndex;
const lookupTable = this.getLookupByIndex(lookupListIndex);
for (let s = 0; s < lookupTable.subtables.length; s++) {
const subtable = lookupTable.subtables[s];
const lookup = this.getLookupMethod(lookupTable, subtable);
const substitutionType = this.getSubstitutionType(lookupTable, subtable);
let subtable = lookupTable.subtables[s];
let lookup;
let substitutionType = this.getSubstitutionType(lookupTable, subtable);

if (substitutionType === '71') {
// This is an extension subtable, so lookup the target subtable
substitutionType = this.getSubstitutionType(subtable, subtable.extension);
lookup = this.getLookupMethod(subtable, subtable.extension);
subtable = subtable.extension;
} else {
lookup = this.getLookupMethod(lookupTable, subtable);
}

if (substitutionType === '12') {
for (let n = 0; n < inputLookups.length; n++) {
const glyphIndex = contextParams.get(n);
const substitution = lookup(glyphIndex);
if (substitution) substitutions.push(substitution);
}
} else {
throw new Error(`Substitution type ${substitutionType} is not supported in chaining substitution`);
}
}
}
Expand Down Expand Up @@ -367,9 +379,19 @@ FeatureQuery.prototype.lookupFeature = function (query) {
const lookupTable = lookups[l];
const subtables = this.getLookupSubtables(lookupTable);
for (let s = 0; s < subtables.length; s++) {
const subtable = subtables[s];
const substType = this.getSubstitutionType(lookupTable, subtable);
const lookup = this.getLookupMethod(lookupTable, subtable);
let subtable = subtables[s];
let substType = this.getSubstitutionType(lookupTable, subtable);
let lookup;

if (substType === '71') {
// This is an extension subtable, so lookup the target subtable
substType = this.getSubstitutionType(subtable, subtable.extension);
lookup = this.getLookupMethod(subtable, subtable.extension);
subtable = subtable.extension;
} else {
lookup = this.getLookupMethod(lookupTable, subtable);
}

let substitution;
switch (substType) {
case '11':
Expand Down