Fix ttf loading problem with Roboto Mono

@@ -17,11 +17,14 @@
  DART_SRC=$(shell find . -name '*.dart')
  CLNG_SRC=$(shell find . -name '*.java' -o -name '*.m' -o -name '*.h')
 
-all: pdf/open-sans.ttf format
+all: pdf/open-sans.ttf pdf/roboto.ttf format
 
 pdf/open-sans.ttf:
 	curl -L "https://github.com/google/fonts/raw/master/apache/opensans/OpenSans-Regular.ttf" > $@
 
+pdf/roboto.ttf:
+	curl -L "https://github.com/google/fonts/raw/master/apache/robotomono/RobotoMono-Regular.ttf" > $@
+
 format: format-dart format-clang
 
 format-dart: $(DART_SRC)

@@ -58,7 +58,8 @@ class PDFTTFFont extends PDFFont {
       return super.glyphAdvance(charCode);
     }
 
-    return (font.advanceWidth[g]) ?? super.glyphAdvance(charCode);
+    return (g < font.advanceWidth.length ? font.advanceWidth[g] : null) ??
+        super.glyphAdvance(charCode);
   }
 
   @override

@@ -30,6 +30,20 @@ void main() {
     g.setColor(new PDFColor(0.3, 0.3, 0.3));
     g.drawString(ttf, FS, s, 50.0, 30.0);
 
+    var roboto = new PDFTTFFont(
+        pdf,
+        (new File("roboto.ttf").readAsBytesSync() as Uint8List)
+            .buffer
+            .asByteData());
+
+    r = roboto.stringBounds(s);
+    print(r);
+    g.setColor(new PDFColor(0.0, 1.0, 1.0));
+    g.drawRect(50.0 + r.x * FS, 130.0 + r.y * FS, r.w * FS, r.h * FS);
+    g.fillPath();
+    g.setColor(new PDFColor(0.3, 0.3, 0.3));
+    g.drawString(roboto, FS, s, 50.0, 130.0);
+
     var file = new File('file2.pdf');
     file.writeAsBytesSync(pdf.save());
   });