Do not modify the TTF font streams

+# 1.3.13
+* Do not modify the TTF font streams
+
 # 1.3.12
 * Fix TextStyle constructor
 

@@ -16,19 +16,28 @@
 
 part of pdf;
 
+@immutable
 class TtfGlyphInfo {
-  TtfGlyphInfo(this.index, this.data, this.compounds);
+  const TtfGlyphInfo(this.index, this.data, this.compounds);
 
   final int index;
   final Uint8List data;
   final List<int> compounds;
 
+  TtfGlyphInfo copy() {
+    return TtfGlyphInfo(
+      index,
+      Uint8List.fromList(data),
+      List<int>.from(compounds),
+    );
+  }
+
   @override
   String toString() => 'Glyph $index $compounds';
 }
 
 class TtfParser {
-  TtfParser(this.bytes) {
+  TtfParser(ByteData bytes) : bytes = UnmodifiableByteDataView(bytes) {
     final int numTables = bytes.getUint16(4);
 
     for (int i = 0; i < numTables; i++) {
@@ -54,7 +63,7 @@ class TtfParser {
   static const String loca_table = 'loca';
   static const String glyf_table = 'glyf';
 
-  final ByteData bytes;
+  final UnmodifiableByteDataView bytes;
   final Map<String, int> tableOffsets = <String, int>{};
   final Map<String, int> tableSize = <String, int>{};
   String _fontName;
@@ -284,7 +293,7 @@ class TtfParser {
       return TtfGlyphInfo(
         glyph,
         Uint8List.view(bytes.buffer, start, offset - start),
-        <int>[],
+        const <int>[],
       );
     }
 
@@ -322,7 +331,7 @@ class TtfParser {
     return TtfGlyphInfo(
       glyph,
       Uint8List.view(bytes.buffer, start, offset - start),
-      <int>[],
+      const <int>[],
     );
   }
 

@@ -62,13 +62,14 @@ class TtfWriter {
 
     for (int index = 0; index < chars.length; index++) {
       if (chars[index] == 32) {
-        final TtfGlyphInfo glyph = TtfGlyphInfo(32, Uint8List(0), <int>[]);
+        final TtfGlyphInfo glyph =
+            TtfGlyphInfo(32, Uint8List(0), const <int>[]);
         glyphsInfo.add(glyph);
         continue;
       }
 
       final TtfGlyphInfo glyph =
-          ttf.readGlyph(ttf.charToGlyphIndexMap[chars[index]] ?? 0);
+          ttf.readGlyph(ttf.charToGlyphIndexMap[chars[index]] ?? 0).copy();
       for (int g in glyph.compounds) {
         compounds[g] = null;
       }
@@ -92,7 +93,7 @@ class TtfWriter {
     }
 
     // Add one last empty glyph
-    final TtfGlyphInfo glyph = TtfGlyphInfo(32, Uint8List(0), <int>[]);
+    final TtfGlyphInfo glyph = TtfGlyphInfo(32, Uint8List(0), const <int>[]);
     glyphsInfo.add(glyph);
 
     // update compound indices

@@ -131,6 +131,9 @@ class Font {
       _pdfFont = buildFont(pdfDocument);
     }
 
+    assert(_pdfFont.pdfDocument == context.document,
+        'Do not reuse a Font object across multiple documents');
+
     return _pdfFont;
   }
 

@@ -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: 1.3.12
+version: 1.3.13
 
 environment:
   sdk: ">=2.1.0 <3.0.0"