Fix Font Subsetting

+# 1.3.6
+* Fix TTF Font SubSetting
+
 # 1.3.5
 * Add some color functions
 * Remove color constants from PdfColor, use PdfColors

@@ -77,13 +77,16 @@ class TtfWriter {
 
     // Add compound glyphs
     for (int compound in compounds.keys) {
-      final int index = chars.indexOf(compound);
-      if (index >= 0) {
-        compounds[compound] = index;
+      final TtfGlyphInfo index = glyphsInfo.firstWhere(
+          (TtfGlyphInfo glyph) => glyph.index == compound,
+          orElse: () => null);
+      if (index != null) {
+        compounds[compound] = glyphsInfo.indexOf(index);
+        assert(compounds[compound] >= 0, 'Unable to find the glyph');
       } else {
         compounds[compound] = glyphsInfo.length;
         final TtfGlyphInfo glyph = ttf.readGlyph(compound);
-        assert(glyph.compounds.isEmpty); // This is a simple glyph
+        assert(glyph.compounds.isEmpty, 'This is not a simple glyph');
         glyphsInfo.add(glyph);
       }
     }

@@ -4,7 +4,7 @@ description: A pdf producer for Dart. It can create pdf files for both web or fl
 homepage: https://github.com/DavBfr/dart_pdf/tree/master/pdf
 repository: https://github.com/DavBfr/dart_pdf
 issue_tracker: https://github.com/DavBfr/dart_pdf/issues
-version: 1.3.5
+version: 1.3.6
 
 environment:
   sdk: ">=2.1.0 <3.0.0"

@@ -75,4 +75,22 @@ void main() {
     final File file = File('ttf.pdf');
     file.writeAsBytesSync(pdf.save());
   });
+
+  test('Font SubSetting', () {
+    final Uint8List fontData = File('open-sans.ttf').readAsBytesSync();
+    final TtfParser font = TtfParser(fontData.buffer.asByteData());
+    final TtfWriter ttfWriter = TtfWriter(font);
+    final Uint8List data = ttfWriter.withChars('hçHée'.runes.toList());
+    final File output = File('${font.fontName}.ttf');
+    output.writeAsBytesSync(data);
+  });
+
+  test('Font SubSetting CN', () {
+    final Uint8List fontData = File('genyomintw.ttf').readAsBytesSync();
+    final TtfParser font = TtfParser(fontData.buffer.asByteData());
+    final TtfWriter ttfWriter = TtfWriter(font);
+    final Uint8List data = ttfWriter.withChars('hçHée 你好 檯號 ☃'.runes.toList());
+    final File output = File('${font.fontName}.ttf');
+    output.writeAsBytesSync(data);
+  });
 }