Add preliminary support for Mac kern table.

This is to support fonts like "Anton" which only have a Mac kern table.
jssuttles · Jan 5, 2017 · a3652cc · a3652cc
1 parent a798444
commit a3652cc
Showing 1 changed file with 45 additions and 9 deletions.
diff --git a/src/tables/kern.js b/src/tables/kern.js
@@ -7,17 +7,13 @@
 var check = require('../check');
 var parse = require('../parse');
 
-// Parse the `kern` table which contains kerning pairs.
-function parseKernTable(data, start) {
+function parseWindowsKernTable(p) {
     var pairs = {};
-    var p = new parse.Parser(data, start);
-    var tableVersion = p.parseUShort();
-    check.argument(tableVersion === 0, 'Unsupported kern table version.');
     // Skip nTables.
-    p.skip('uShort', 1);
-    var subTableVersion = p.parseUShort();
-    check.argument(subTableVersion === 0, 'Unsupported kern sub-table version.');
-    // Skip subTableLength, subTableCoverage
+    p.skip('uShort');
+    var subtableVersion = p.parseUShort();
+    check.argument(subtableVersion === 0, 'Unsupported kern sub-table version.');
+    // Skip subtableLength, subtableCoverage
     p.skip('uShort', 2);
     var nPairs = p.parseUShort();
     // Skip searchRange, entrySelector, rangeShift.
@@ -28,8 +24,48 @@ function parseKernTable(data, start) {
         var value = p.parseShort();
         pairs[leftIndex + ',' + rightIndex] = value;
     }
+    return pairs;
+}
 
+function parseMacKernTable(p) {
+    var pairs = {};
+    // The Mac kern table stores the version as a fixed (32 bits) but we only loaded the first 16 bits.
+    // Skip the rest.
+    p.skip('uShort');
+    var nTables = p.parseULong();
+    //check.argument(nTables === 1, 'Only 1 subtable is supported (got ' + nTables + ').');
+    if (nTables > 1) {
+        console.warn('Only the first kern subtable is supported.');
+    }
+    p.skip('uLong');
+    var coverage = p.parseUShort();
+    var subtableVersion = coverage & 0xFF;
+    p.skip('uShort');
+    if (subtableVersion === 0) {
+        var nPairs = p.parseUShort();
+        // Skip searchRange, entrySelector, rangeShift.
+        p.skip('uShort', 3);
+        for (var i = 0; i < nPairs; i += 1) {
+            var leftIndex = p.parseUShort();
+            var rightIndex = p.parseUShort();
+            var value = p.parseShort();
+            pairs[leftIndex + ',' + rightIndex] = value;
+        }
+    }
     return pairs;
 }
 
+// Parse the `kern` table which contains kerning pairs.
+function parseKernTable(data, start) {
+    var p = new parse.Parser(data, start);
+    var tableVersion = p.parseUShort();
+    if (tableVersion === 0) {
+        return parseWindowsKernTable(p);
+    } else if (tableVersion === 1) {
+        return parseMacKernTable(p);
+    } else {
+        throw new Error('Unsupported kern table version (' + tableVersion + ').');
+    }
+}
+
 exports.parse = parseKernTable;