implement support and tests for cmap format 13

src/tables/cmap.js

@@ -24,7 +24,7 @@ function parseCmapTableFormat0(cmap, p, platformID, encodingID) {
     cmap.glyphIndexMap = glyphIndexMap;
 }
 
-function parseCmapTableFormat12(cmap, p) {
+function parseCmapTableFormat12or13(cmap, p, format) {
     //Skip reserved.
     p.parseUShort();
 
@@ -43,7 +43,9 @@ function parseCmapTableFormat12(cmap, p) {
 
         for (let c = startCharCode; c <= endCharCode; c += 1) {
             cmap.glyphIndexMap[c] = startGlyphId;
-            startGlyphId++;
+            if (format === 12) {
+                startGlyphId++;
+            }
         }
     }
 }
@@ -171,11 +173,13 @@ function parseCmapTable(data, start) {
     let offset = -1;
     let platformId = null;
     let encodingId = null;
+    const platform0Encodings = [0,1,2,3,4,6];
+    const platform3Encodings = [0,1,10];
     for (let i = cmap.numTables - 1; i >= 0; i -= 1) {
         platformId = parse.getUShort(data, start + 4 + (i * 8));
         encodingId = parse.getUShort(data, start + 4 + (i * 8) + 2);
-        if ((platformId === 3 && (encodingId === 0 || encodingId === 1 || encodingId === 10)) ||
-            (platformId === 0 && (encodingId === 0 || encodingId === 1 || encodingId === 2 || encodingId === 3 || encodingId === 4)) ||
+        if ((platformId === 3 && platform3Encodings.includes(encodingId)) ||
+            (platformId === 0 && platform0Encodings.includes(encodingId)) ||
             (platformId === 1 && encodingId === 0) // MacOS <= 9
         ) {
             offset = parse.getULong(data, start + 4 + (i * 8) + 4);
@@ -203,8 +207,8 @@ function parseCmapTable(data, start) {
 
     if (cmap.format === 0) {
         parseCmapTableFormat0(cmap, p, platformId, encodingId);
-    } else if (cmap.format === 12) {
-        parseCmapTableFormat12(cmap, p);
+    } else if (cmap.format === 12 || cmap.format === 13) {
+        parseCmapTableFormat12or13(cmap, p, cmap.format);
     } else if (cmap.format === 4) {
         parseCmapTableFormat4(cmap, p, data, start, offset);
     } else {

test/fonts/LICENSE

@@ -36,11 +36,15 @@ SourceSansPro-Regular.otf
     SIL Open Font License, Version 1.1
     https://www.fontsquirrel.com/license/source-sans-pro
 
+TestCMAP13.otf
+    Copyright 2023 Unicode Inc. All rights reserved.
+    SIL Open Font License version 1.1 (OFL-1.1)
+    https://opensource.org/licenses/OFL-1.1
+
 TestCMAP14.otf
     Copyright 2016 Unicode Inc. All rights reserved.
-    Apache License, Version 2.0
-    http://www.apache.org/licenses/LICENSE-2.0
-    https://github.com/unicode-org/text-rendering-tests/blob/main/LICENSE.md
+    SIL Open Font License
+    http://scripts.sil.org/OFL
 
 TestCMAPMacTurkish.ttf
     Copyright © 2016 by Unicode Inc.

test/tables/cmap.js

@@ -71,4 +71,15 @@ describe('tables/cmap.js', function() {
         }
         assert.deepEqual(glyphIds, expectedGlyphIds);
     });
+
+    it('can parse CMAP table format 13', function() {
+        let font;
+        assert.doesNotThrow(function() {
+            font = loadSync('./test/fonts/TestCMAP13.ttf');
+        });
+        const testString = 'U\u13EF\u{1203C}\u{1FA00}';
+        const glyphIds = font.stringToGlyphIndexes(testString);
+        const expectedGlyphIds = [1,2,3,4];
+        assert.deepEqual(glyphIds, expectedGlyphIds);
+    });
 });