Use runes to get code units in CanvasKit.

lib/web_ui/dev/goldens_lock.yaml

@@ -1,2 +1,2 @@
 repository: https://github.com/flutter/goldens.git
-revision: d70eca62b254302b293973573d3b16ffd05b19db
+revision: 44f00682eee2afd7042c02ce802199c1c4ff223e

lib/web_ui/dev/test_runner.dart

@@ -92,8 +92,7 @@ class TestCommand extends Command<bool> with ArgUtils {
         'fetch-goldens-repo',
         defaultsTo: true,
         negatable: true,
-        help:
-            'Whether to fetch the goldens repo. Set this to false to iterate '
+        help: 'Whether to fetch the goldens repo. Set this to false to iterate '
             'on golden tests without fearing that the fetcher will overwrite '
             'your local changes.',
       )
@@ -174,39 +173,41 @@ class TestCommand extends Command<bool> with ArgUtils {
       final FilePath dir = FilePath.fromWebUi('');
       print('');
       print('Initial test run is done!');
-      print('Watching ${dir.relativeToCwd}/lib and ${dir.relativeToCwd}/test to re-run tests');
+      print(
+          'Watching ${dir.relativeToCwd}/lib and ${dir.relativeToCwd}/test to re-run tests');
       print('');
       PipelineWatcher(
-        dir: dir.absolute,
-        pipeline: testPipeline,
-        ignore: (event) {
-          // Ignore font files that are copied whenever tests run.
-          if (event.path.endsWith('.ttf')) {
-            return true;
-          }
+          dir: dir.absolute,
+          pipeline: testPipeline,
+          ignore: (event) {
+            // Ignore font files that are copied whenever tests run.
+            if (event.path.endsWith('.ttf')) {
+              return true;
+            }
 
-          // Ignore auto-generated JS files.
-          // The reason we are using `.contains()` instead of `.endsWith()` is
-          // because the auto-generated files could end with any of the
-          // following:
-          //
-          // - browser_test.dart.js
-          // - browser_test.dart.js.map
-          // - browser_test.dart.js.deps
-          if (event.path.contains('browser_test.dart.js')) {
-            return true;
-          }
+            // Ignore auto-generated JS files.
+            // The reason we are using `.contains()` instead of `.endsWith()` is
+            // because the auto-generated files could end with any of the
+            // following:
+            //
+            // - browser_test.dart.js
+            // - browser_test.dart.js.map
+            // - browser_test.dart.js.deps
+            if (event.path.contains('browser_test.dart.js')) {
+              return true;
+            }
 
-          // React to changes in lib/ and test/ folders.
-          final String relativePath = path.relative(event.path, from: dir.absolute);
-          if (relativePath.startsWith('lib/') || relativePath.startsWith('test/')) {
-            return false;
-          }
+            // React to changes in lib/ and test/ folders.
+            final String relativePath =
+                path.relative(event.path, from: dir.absolute);
+            if (relativePath.startsWith('lib/') ||
+                relativePath.startsWith('test/')) {
+              return false;
+            }
 
-          // Ignore anything else.
-          return true;
-        }
-      ).start();
+            // Ignore anything else.
+            return true;
+          }).start();
       // Return a never-ending future.
       return Completer<bool>().future;
     } else {
@@ -226,15 +227,17 @@ class TestCommand extends Command<bool> with ArgUtils {
             bool unitTestResult = await runUnitTests();
             bool integrationTestResult = await runIntegrationTests();
             if (integrationTestResult != unitTestResult) {
-              print('Tests run. Integration tests passed: $integrationTestResult '
+              print(
+                  'Tests run. Integration tests passed: $integrationTestResult '
                   'unit tests passed: $unitTestResult');
             }
             return integrationTestResult && unitTestResult;
           } else {
             return await runUnitTests();
           }
       }
-      throw UnimplementedError('Unknown test type requested: $testTypesRequested');
+      throw UnimplementedError(
+          'Unknown test type requested: $testTypesRequested');
     } on TestFailureException {
       return true;
     }
@@ -786,6 +789,7 @@ const List<String> _kTestFonts = <String>[
   'ahem.ttf',
   'Roboto-Regular.ttf',
   'NotoNaskhArabic-Regular.ttf',
+  'NotoColorEmoji.ttf',
 ];
 
 void _copyTestFontsIntoWebUi() {

lib/web_ui/lib/src/engine/canvaskit/font_fallbacks.dart

@@ -211,15 +211,19 @@ Future<void> _registerSymbolsAndEmoji() async {
   String? symbolsFontUrl = extractUrlFromCss(symbolsCss);
   String? emojiFontUrl = extractUrlFromCss(emojiCss);
 
-  if (symbolsFontUrl == null || emojiFontUrl == null) {
-    html.window.console
-        .warn('Error parsing CSS for Noto Emoji and Symbols font.');
+  if (symbolsFontUrl != null) {
+    notoDownloadQueue.add(_ResolvedNotoSubset(
+        symbolsFontUrl, 'Noto Sans Symbols', const <CodeunitRange>[]));
+  } else {
+    html.window.console.warn('Error parsing CSS for Noto Symbols font.');
   }
 
-  notoDownloadQueue.add(_ResolvedNotoSubset(
-      symbolsFontUrl!, 'Noto Sans Symbols', const <CodeunitRange>[]));
-  notoDownloadQueue.add(_ResolvedNotoSubset(
-      emojiFontUrl!, 'Noto Color Emoji Compat', const <CodeunitRange>[]));
+  if (emojiFontUrl != null) {
+    notoDownloadQueue.add(_ResolvedNotoSubset(
+        emojiFontUrl, 'Noto Color Emoji Compat', const <CodeunitRange>[]));
+  } else {
+    html.window.console.warn('Error parsing CSS for Noto Emoji font.');
+  }
 }
 
 /// Finds the minimum set of fonts which covers all of the [codeunits].
@@ -695,9 +699,10 @@ class NotoDownloader {
     if (assertionsEnabled) {
       _debugActiveDownloadCount += 1;
     }
-    final Future<ByteBuffer> result = html.window.fetch(url).then((dynamic fetchResult) => fetchResult
-        .arrayBuffer()
-        .then<ByteBuffer>((dynamic x) => x as ByteBuffer));
+    final Future<ByteBuffer> result = html.window.fetch(url).then(
+        (dynamic fetchResult) => fetchResult
+            .arrayBuffer()
+            .then<ByteBuffer>((dynamic x) => x as ByteBuffer));
     if (assertionsEnabled) {
       result.whenComplete(() {
         _debugActiveDownloadCount -= 1;
@@ -713,8 +718,9 @@ class NotoDownloader {
     if (assertionsEnabled) {
       _debugActiveDownloadCount += 1;
     }
-    final Future<String> result = html.window.fetch(url).then((dynamic response) =>
-        response.text().then<String>((dynamic x) => x as String));
+    final Future<String> result = html.window.fetch(url).then(
+        (dynamic response) =>
+            response.text().then<String>((dynamic x) => x as String));
     if (assertionsEnabled) {
       result.whenComplete(() {
         _debugActiveDownloadCount -= 1;

lib/web_ui/lib/src/engine/canvaskit/text.dart

@@ -20,7 +20,7 @@ class CkParagraphStyle implements ui.ParagraphStyle {
     ui.StrutStyle? strutStyle,
     String? ellipsis,
     ui.Locale? locale,
-  }) : skParagraphStyle = toSkParagraphStyle(
+  })  : skParagraphStyle = toSkParagraphStyle(
           textAlign,
           textDirection,
           maxLines,
@@ -34,11 +34,11 @@ class CkParagraphStyle implements ui.ParagraphStyle {
           ellipsis,
           locale,
         ),
-      _textDirection = textDirection ?? ui.TextDirection.ltr,
-      _fontFamily = fontFamily,
-      _fontSize = fontSize,
-      _fontWeight = fontWeight,
-      _fontStyle = fontStyle;
+        _textDirection = textDirection ?? ui.TextDirection.ltr,
+        _fontFamily = fontFamily,
+        _fontSize = fontSize,
+        _fontWeight = fontWeight,
+        _fontStyle = fontStyle;
 
   final SkParagraphStyle skParagraphStyle;
   final ui.TextDirection? _textDirection;
@@ -276,13 +276,14 @@ class CkTextStyle implements ui.TextStyle {
   }
 
   /// Lazy-initialized list of font families sent to Skia.
-  late final List<String> effectiveFontFamilies = _getEffectiveFontFamilies(fontFamily, fontFamilyFallback);
+  late final List<String> effectiveFontFamilies =
+      _getEffectiveFontFamilies(fontFamily, fontFamilyFallback);
 
   /// Lazy-initialized Skia style used to pass the style to Skia.
   ///
   /// This is lazy because not every style ends up being passed to Skia, so the
   /// conversion would be wasteful.
-  late final SkTextStyle  skTextStyle = () {
+  late final SkTextStyle skTextStyle = () {
     // Write field values to locals so null checks promote types to non-null.
     final ui.Color? color = this.color;
     final ui.TextDecoration? decoration = this.decoration;
@@ -695,22 +696,22 @@ class CkParagraphBuilder implements ui.ParagraphBuilder {
         typefaces.addAll(typefacesForFamily);
       }
     }
-    List<bool> codeUnitsSupported = List<bool>.filled(text.length, false);
+    List<int> codeUnits = text.runes.toList();
+    List<bool> codeUnitsSupported = List<bool>.filled(codeUnits.length, false);
     for (SkTypeface typeface in typefaces) {
       SkFont font = SkFont(typeface);
       Uint8List glyphs = font.getGlyphIDs(text);
       assert(glyphs.length == codeUnitsSupported.length);
       for (int i = 0; i < glyphs.length; i++) {
-        codeUnitsSupported[i] |=
-            glyphs[i] != 0 || _isControlCode(text.codeUnitAt(i));
+        codeUnitsSupported[i] |= glyphs[i] != 0 || _isControlCode(codeUnits[i]);
       }
     }
 
     if (codeUnitsSupported.any((x) => !x)) {
       List<int> missingCodeUnits = <int>[];
       for (int i = 0; i < codeUnitsSupported.length; i++) {
         if (!codeUnitsSupported[i]) {
-          missingCodeUnits.add(text.codeUnitAt(i));
+          missingCodeUnits.add(codeUnits[i]);
         }
       }
       _findFontsForMissingCodeunits(missingCodeUnits);
@@ -778,7 +779,8 @@ class CkParagraphBuilder implements ui.ParagraphBuilder {
   // This object is never deleted. It is effectively a static global constant.
   // Therefore it doesn't need to be wrapped in CkPaint.
   static final SkPaint _defaultTextForeground = SkPaint();
-  static final SkPaint _defaultTextBackground = SkPaint()..setColorInt(0x00000000);
+  static final SkPaint _defaultTextBackground = SkPaint()
+    ..setColorInt(0x00000000);
 
   @override
   void pushStyle(ui.TextStyle style) {
@@ -796,7 +798,8 @@ class CkParagraphBuilder implements ui.ParagraphBuilder {
         foreground = _defaultTextForeground;
       }
 
-      final SkPaint background = skStyle.background?.skiaObject ?? _defaultTextBackground;
+      final SkPaint background =
+          skStyle.background?.skiaObject ?? _defaultTextBackground;
       _paragraphBuilder.pushPaintStyle(
           skStyle.skTextStyle, foreground, background);
     } else {

lib/web_ui/test/canvaskit/fallback_fonts_golden_test.dart

@@ -19,7 +19,7 @@ void main() {
   internalBootstrapBrowserTest(() => testMain);
 }
 
-const ui.Rect kDefaultRegion = const ui.Rect.fromLTRB(0, 0, 500, 250);
+const ui.Rect kDefaultRegion = const ui.Rect.fromLTRB(0, 0, 100, 50);
 
 Future<void> matchPictureGolden(String goldenFile, CkPicture picture,
     {ui.Rect region = kDefaultRegion, bool write = false}) async {
@@ -105,22 +105,86 @@ void testMain() {
       final CkCanvas canvas = recorder.beginRecording(kDefaultRegion);
 
       pb = CkParagraphBuilder(
-        CkParagraphStyle(
-          fontSize: 32,
-        ),
+        CkParagraphStyle(),
       );
+      pb.pushStyle(ui.TextStyle(fontSize: 32));
       pb.addText('مرحبا');
+      pb.pop();
       final CkParagraph paragraph = pb.build();
       paragraph.layout(ui.ParagraphConstraints(width: 1000));
 
-      canvas.drawParagraph(paragraph, ui.Offset(200, 120));
+      canvas.drawParagraph(paragraph, ui.Offset(0, 0));
 
       await matchPictureGolden(
           'canvaskit_font_fallback_arabic.png', recorder.endRecording());
       // TODO: https://github.com/flutter/flutter/issues/60040
       // TODO: https://github.com/flutter/flutter/issues/71520
     }, skip: isIosSafari || isFirefox);
 
+    test('will download Noto Emojis and Noto Symbols if no matching Noto Font',
+        () async {
+      final Completer<void> fontChangeCompleter = Completer<void>();
+      // Intercept the system font change message.
+      ui.window.onPlatformMessage = (String name, ByteData? data,
+          ui.PlatformMessageResponseCallback? callback) {
+        if (name == 'flutter/system') {
+          const JSONMessageCodec codec = JSONMessageCodec();
+          final dynamic message = codec.decodeMessage(data);
+          if (message is Map) {
+            if (message['type'] == 'fontsChange') {
+              fontChangeCompleter.complete();
+            }
+          }
+        }
+        if (savedCallback != null) {
+          savedCallback!(name, data, callback);
+        }
+      };
+
+      TestDownloader.mockDownloads[
+              'https://fonts.googleapis.com/css2?family=Noto+Color+Emoji+Compat'] =
+          '''
+/* arabic */
+@font-face {
+  font-family: 'Noto Color Emoji';
+  src: url(packages/ui/assets/NotoColorEmoji.ttf) format('ttf');
+}
+''';
+
+      expect(skiaFontCollection.globalFontFallbacks, ['Roboto']);
+
+      // Creating this paragraph should cause us to start to download the
+      // fallback font.
+      CkParagraphBuilder pb = CkParagraphBuilder(
+        CkParagraphStyle(),
+      );
+      pb.addText('Hello 😊');
+
+      await fontChangeCompleter.future;
+
+      expect(skiaFontCollection.globalFontFallbacks,
+          contains('Noto Color Emoji Compat 0'));
+
+      final CkPictureRecorder recorder = CkPictureRecorder();
+      final CkCanvas canvas = recorder.beginRecording(kDefaultRegion);
+
+      pb = CkParagraphBuilder(
+        CkParagraphStyle(),
+      );
+      pb.pushStyle(ui.TextStyle(fontSize: 26));
+      pb.addText('Hello 😊');
+      pb.pop();
+      final CkParagraph paragraph = pb.build();
+      paragraph.layout(ui.ParagraphConstraints(width: 1000));
+
+      canvas.drawParagraph(paragraph, ui.Offset(0, 0));
+
+      await matchPictureGolden(
+          'canvaskit_font_fallback_emoji.png', recorder.endRecording());
+      // TODO: https://github.com/flutter/flutter/issues/60040
+      // TODO: https://github.com/flutter/flutter/issues/71520
+    }, skip: isIosSafari || isFirefox);
+
     test('will gracefully fail if we cannot parse the Google Fonts CSS',
         () async {
       TestDownloader.mockDownloads[