Add a default theme initializer

@@ -8,6 +8,7 @@
 - Fix TTF font parser for NewsCycle-Regular.ttf
 - Fix AssetManifest
 - Update Google Fonts
+- Add a default theme initializer
 
 ## 5.6.6
 

@@ -14,6 +14,10 @@
  * limitations under the License.
  */
 
+import 'package:pdf/widgets.dart';
+
+import 'src/fonts/gfonts.dart';
+
 export 'src/asset_utils.dart';
 export 'src/cache.dart';
 export 'src/callback.dart';
@@ -25,3 +29,27 @@ export 'src/printing.dart';
 export 'src/printing_info.dart';
 export 'src/raster.dart';
 export 'src/widget_wrapper.dart';
+
+Future<void> pdfDefaultTheme() async {
+  if (ThemeData.buildThemeData != null) {
+    return;
+  }
+
+  final base = await PdfGoogleFonts.openSansRegular();
+  final bold = await PdfGoogleFonts.openSansBold();
+  final italic = await PdfGoogleFonts.openSansItalic();
+  final boldItalic = await PdfGoogleFonts.openSansBoldItalic();
+  final emoji = await PdfGoogleFonts.notoColorEmoji();
+  final icons = await PdfGoogleFonts.materialIcons();
+
+  ThemeData.buildThemeData = () {
+    return ThemeData.withFont(
+      base: base,
+      bold: bold,
+      italic: italic,
+      boldItalic: boldItalic,
+      icons: icons,
+      fontFallback: [emoji, base],
+    );
+  };
+}