Add support for system text scale factor. (#4124)

Adds support for system text scale factor, including hooks for Android system settings changes.  iOS hooks will be added in another PR.

lib/ui/hooks.dart

@@ -32,6 +32,11 @@ void _updateLocale(String languageCode, String countryCode) {
   _invoke(window.onLocaleChanged, window._onLocaleChangedZone);
 }
 
+void _updateTextScaleFactor(double textScaleFactor) {
+  window._textScaleFactor = textScaleFactor;
+  _invoke(window.onTextScaleFactorChanged, window._onTextScaleFactorChangedZone);
+}
+
 void _updateSemanticsEnabled(bool enabled) {
   window._semanticsEnabled = enabled;
   _invoke(window.onSemanticsEnabledChanged, window._onSemanticsEnabledChangedZone);

lib/ui/window.dart

@@ -254,6 +254,38 @@ class Window {
     _onLocaleChangedZone = Zone.current;
   }
 
+  /// The system-reported text scale.
+  ///
+  /// This establishes the text scaling factor to use when rendering text,
+  /// according to the user's platform preferences.
+  ///
+  /// The [onTextScaleFactorChanged] callback is called whenever this value
+  /// changes.
+  ///
+  /// See also:
+  ///
+  ///  * [WidgetsBindingObserver], for a mechanism at the widgets layer to
+  ///    observe when this value changes.
+  double get textScaleFactor => _textScaleFactor;
+  double _textScaleFactor = 1.0;
+
+  /// A callback that is invoked whenever [textScaleFactor] changes value.
+  ///
+  /// The framework invokes this callback in the same zone in which the
+  /// callback was set.
+  ///
+  /// See also:
+  ///
+  ///  * [WidgetsBindingObserver], for a mechanism at the widgets layer to
+  ///    observe when this callback is invoked.
+  VoidCallback get onTextScaleFactorChanged => _onTextScaleFactorChanged;
+  VoidCallback _onTextScaleFactorChanged;
+  Zone _onTextScaleFactorChangedZone;
+  set onTextScaleFactorChanged(VoidCallback callback) {
+    _onTextScaleFactorChanged = callback;
+    _onTextScaleFactorChangedZone = Zone.current;
+  }
+
   /// A callback that is invoked to notify the application that it is an
   /// appropriate time to provide a scene using the [SceneBuilder] API and the
   /// [render] method. When possible, this is driven by the hardware VSync

lib/ui/window/window.cc

@@ -163,6 +163,18 @@ void Window::UpdateLocale(const std::string& language_code,
                   });
 }
 
+void Window::UpdateTextScaleFactor(double text_scale_factor) {
+  tonic::DartState* dart_state = library_.dart_state().get();
+  if (!dart_state)
+    return;
+  tonic::DartState::Scope scope(dart_state);
+
+  DartInvokeField(library_.value(), "_updateTextScaleFactor",
+                  {
+                      ToDart(static_cast<double>(text_scale_factor)),
+                  });
+}
+
 void Window::UpdateSemanticsEnabled(bool enabled) {
   tonic::DartState* dart_state = library_.dart_state().get();
   if (!dart_state)

lib/ui/window/window.h

@@ -45,6 +45,7 @@ class Window {
   void UpdateWindowMetrics(const ViewportMetrics& metrics);
   void UpdateLocale(const std::string& language_code,
                     const std::string& country_code);
+  void UpdateTextScaleFactor(double text_scale_factor);
   void UpdateSemanticsEnabled(bool enabled);
   void DispatchPlatformMessage(fxl::RefPtr<PlatformMessage> message);
   void DispatchPointerDataPacket(const PointerDataPacket& packet);

runtime/runtime_controller.cc

@@ -66,6 +66,13 @@ void RuntimeController::SetLocale(const std::string& language_code,
   GetWindow()->UpdateLocale(language_code_, country_code_);
 }
 
+void RuntimeController::SetTextScaleFactor(double text_scale_factor) {
+  if (text_scale_factor_ == text_scale_factor)
+    return;
+  text_scale_factor_ = text_scale_factor;
+  GetWindow()->UpdateTextScaleFactor(text_scale_factor_);
+}
+
 void RuntimeController::SetSemanticsEnabled(bool enabled) {
   if (semantics_enabled_ == enabled)
     return;

runtime/runtime_controller.h

@@ -35,6 +35,7 @@ class RuntimeController : public WindowClient, public IsolateClient {
   void SetViewportMetrics(const ViewportMetrics& metrics);
   void SetLocale(const std::string& language_code,
                  const std::string& country_code);
+  void SetTextScaleFactor(double textScaleFactor);
   void SetSemanticsEnabled(bool enabled);
 
   void BeginFrame(fxl::TimePoint frame_time);
@@ -66,6 +67,7 @@ class RuntimeController : public WindowClient, public IsolateClient {
   RuntimeDelegate* client_;
   std::string language_code_;
   std::string country_code_;
+  double text_scale_factor_ = 1.0;
   bool semantics_enabled_ = false;
   std::unique_ptr<DartController> dart_controller_;
 

shell/common/engine.cc

@@ -44,6 +44,7 @@ constexpr char kAssetChannel[] = "flutter/assets";
 constexpr char kLifecycleChannel[] = "flutter/lifecycle";
 constexpr char kNavigationChannel[] = "flutter/navigation";
 constexpr char kLocalizationChannel[] = "flutter/localization";
+constexpr char kSystemChannel[] = "flutter/system";
 
 bool PathExists(const std::string& path) {
   return access(path.c_str(), R_OK) == 0;
@@ -74,6 +75,7 @@ Engine::Engine(PlatformView* platform_view)
           platform_view->GetVsyncWaiter(),
           this)),
       load_script_error_(tonic::kNoError),
+      text_scale_factor_(1.0),
       activity_running_(false),
       have_surface_(false),
       weak_factory_(this) {}
@@ -312,7 +314,12 @@ void Engine::DispatchPlatformMessage(
     if (HandleLifecyclePlatformMessage(message.get()))
       return;
   } else if (message->channel() == kLocalizationChannel) {
-    if (HandleLocalizationPlatformMessage(std::move(message)))
+    if (HandleLocalizationPlatformMessage(message.get()))
+      return;
+  } else if (message->channel() == kSystemChannel) {
+    // This only handles textScaleFactor changes: other system messages are
+    // handled by DispatchPlatformMessage below.
+    if (HandleSystemPlatformMessage(message.get()))
       return;
   }
 
@@ -367,7 +374,7 @@ bool Engine::HandleNavigationPlatformMessage(
 }
 
 bool Engine::HandleLocalizationPlatformMessage(
-    fxl::RefPtr<blink::PlatformMessage> message) {
+    blink::PlatformMessage* message) {
   const auto& data = message->data();
 
   rapidjson::Document document;
@@ -396,6 +403,37 @@ bool Engine::HandleLocalizationPlatformMessage(
   return true;
 }
 
+bool Engine::HandleSystemPlatformMessage(blink::PlatformMessage* message) {
+  const auto& data = message->data();
+  rapidjson::Document document;
+  document.Parse(reinterpret_cast<const char*>(data.data()), data.size());
+
+  if (document.HasParseError() || !document.IsObject())
+    return false;
+
+  auto root = document.GetObject();
+  auto type = root.FindMember("type");
+  if (type == root.MemberEnd() || type->value != "systemSettings")
+    return false;
+
+  // This only handles textScaleFactor changes: other system messages
+  // are handled by DispatchPlatformMessage.
+  auto text_scale_factor = root.FindMember("textScaleFactor");
+  if (text_scale_factor == root.MemberEnd() ||
+      !text_scale_factor->value.IsDouble()) {
+    return false;
+  }
+  text_scale_factor_ = text_scale_factor->value.GetDouble();
+  if (runtime_) {
+    runtime_->SetTextScaleFactor(text_scale_factor_);
+    if (have_surface_)
+      ScheduleFrame();
+  }
+  // If the only members were "type" and "textScaleFactor", then we're done.
+  // If there are more members, then we need to send it on to other handlers.
+  return root.MemberCount() == 2;
+}
+
 void Engine::DispatchPointerDataPacket(const PointerDataPacket& packet) {
   if (runtime_)
     runtime_->DispatchPointerDataPacket(packet);
@@ -445,6 +483,7 @@ void Engine::ConfigureRuntime(const std::string& script_uri,
       default_isolate_snapshot_instr, platform_kernel);
   runtime_->SetViewportMetrics(viewport_metrics_);
   runtime_->SetLocale(language_code_, country_code_);
+  runtime_->SetTextScaleFactor(text_scale_factor_);
   runtime_->SetSemanticsEnabled(semantics_enabled_);
 }
 

shell/common/engine.h

@@ -92,8 +92,8 @@ class Engine : public blink::RuntimeDelegate {
   bool HandleLifecyclePlatformMessage(blink::PlatformMessage* message);
   bool HandleNavigationPlatformMessage(
       fxl::RefPtr<blink::PlatformMessage> message);
-  bool HandleLocalizationPlatformMessage(
-      fxl::RefPtr<blink::PlatformMessage> message);
+  bool HandleLocalizationPlatformMessage(blink::PlatformMessage* message);
+  bool HandleSystemPlatformMessage(blink::PlatformMessage* message);
 
   void HandleAssetPlatformMessage(fxl::RefPtr<blink::PlatformMessage> message);
   bool GetAssetAsBuffer(const std::string& name, std::vector<uint8_t>* data);
@@ -106,6 +106,7 @@ class Engine : public blink::RuntimeDelegate {
   blink::ViewportMetrics viewport_metrics_;
   std::string language_code_;
   std::string country_code_;
+  double text_scale_factor_;
   bool semantics_enabled_ = false;
   // TODO(abarth): Unify these two behind a common interface.
   fxl::RefPtr<blink::ZipAssetStore> asset_store_;

shell/platform/android/AndroidManifest.xml

@@ -11,7 +11,7 @@
     <uses-feature android:name="android.hardware.sensor.accelerometer" android:required="true" />
 
     <application android:label="Flutter Shell" android:name="FlutterApplication" android:debuggable="true">
-        <activity android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection"
+        <activity android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale"
                   android:hardwareAccelerated="true"
                   android:launchMode="standard"
                   android:name="FlutterActivity"

shell/platform/android/io/flutter/view/FlutterView.java

@@ -181,6 +181,7 @@ public class FlutterView extends SurfaceView
         mTextInputPlugin = new TextInputPlugin(this);
 
         setLocale(getResources().getConfiguration().locale);
+        setTextScaleFactor(getResources().getConfiguration().fontScale);
 
         if ((context.getApplicationInfo().flags & ApplicationInfo.FLAG_DEBUGGABLE) != 0) {
             mDiscoveryReceiver = new DiscoveryReceiver();
@@ -278,6 +279,13 @@ public class FlutterView extends SurfaceView
         mFlutterNavigationChannel.invokeMethod("popRoute", null);
     }
 
+    private void setTextScaleFactor(float textScaleFactor) {
+      Map<String, Object> message = new HashMap<>();
+      message.put("type", "systemSettings");
+      message.put("textScaleFactor", textScaleFactor);
+      mFlutterSystemChannel.send(message);
+    }
+    
     private void setLocale(Locale locale) {
         mFlutterLocalizationChannel.invokeMethod("setLocale",
             Arrays.asList(locale.getLanguage(), locale.getCountry()));
@@ -287,6 +295,7 @@ public class FlutterView extends SurfaceView
     protected void onConfigurationChanged(Configuration newConfig) {
         super.onConfigurationChanged(newConfig);
         setLocale(newConfig.locale);
+        setTextScaleFactor(newConfig.fontScale);
     }
 
     float getDevicePixelRatio() {

testing/dart/window_hooks_integration_test.dart

@@ -34,6 +34,7 @@ void main() {
     VoidCallback originalOnSemanticsEnabledChanged;
     SemanticsActionCallback originalOnSemanticsAction;
     PlatformMessageCallback originalOnPlatformMessage;
+    VoidCallback originalOnTextScaleFactorChanged;
 
     setUp(() {
       originalOnMetricsChanged = window.onMetricsChanged;
@@ -44,6 +45,7 @@ void main() {
       originalOnSemanticsEnabledChanged = window.onSemanticsEnabledChanged;
       originalOnSemanticsAction = window.onSemanticsAction;
       originalOnPlatformMessage = window.onPlatformMessage;
+      originalOnTextScaleFactorChanged = window.onTextScaleFactorChanged;
     });
 
     tearDown(() {
@@ -55,55 +57,65 @@ void main() {
       window.onSemanticsEnabledChanged = originalOnSemanticsEnabledChanged;
       window.onSemanticsAction = originalOnSemanticsAction;
       window.onPlatformMessage = originalOnPlatformMessage;
+      window.onTextScaleFactorChanged = originalOnTextScaleFactorChanged;
     });
 
     test('onMetricsChanged preserves callback zone', () {
       Zone innerZone;
       Zone runZone;
+      double devicePixelRatio;
 
       runZoned(() {
         innerZone = Zone.current;
         window.onMetricsChanged = () {
           runZone = Zone.current;
+          devicePixelRatio = window.devicePixelRatio;
         };
       });
 
       window.onMetricsChanged();
-      _updateWindowMetrics(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
+      _updateWindowMetrics(0.1234, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
       expect(runZone, isNotNull);
       expect(runZone, same(innerZone));
+      expect(devicePixelRatio, equals(0.1234));
     });
 
     test('onLocaleChanged preserves callback zone', () {
       Zone innerZone;
       Zone runZone;
+      Locale locale;
 
       runZoned(() {
         innerZone = Zone.current;
         window.onLocaleChanged = () {
           runZone = Zone.current;
+          locale = window.locale;
         };
       });
 
       _updateLocale('en', 'US');
       expect(runZone, isNotNull);
       expect(runZone, same(innerZone));
+      expect(locale, equals(const Locale('en', 'US')));
     });
 
     test('onBeginFrame preserves callback zone', () {
       Zone innerZone;
       Zone runZone;
+      Duration start;
 
       runZoned(() {
         innerZone = Zone.current;
-        window.onBeginFrame = (_) {
+        window.onBeginFrame = (Duration value) {
           runZone = Zone.current;
+          start = value;
         };
       });
 
-      _beginFrame(0);
+      _beginFrame(1234);
       expect(runZone, isNotNull);
       expect(runZone, same(innerZone));
+      expect(start, equals(const Duration(microseconds: 1234)));
     });
 
     test('onDrawFrame preserves callback zone', () {
@@ -125,65 +137,99 @@ void main() {
     test('onPointerDataPacket preserves callback zone', () {
       Zone innerZone;
       Zone runZone;
+      PointerDataPacket data;
 
       runZoned(() {
         innerZone = Zone.current;
-        window.onPointerDataPacket = (_) {
+        window.onPointerDataPacket = (PointerDataPacket value) {
           runZone = Zone.current;
+          data = value;
         };
       });
 
-      _dispatchPointerDataPacket(new ByteData.view(new Uint8List(0).buffer));
+      final ByteData testData = new ByteData.view(new Uint8List(0).buffer);
+      _dispatchPointerDataPacket(testData);
       expect(runZone, isNotNull);
       expect(runZone, same(innerZone));
+      expect(data.data, equals(_unpackPointerDataPacket(testData).data));
     });
 
     test('onSemanticsEnabledChanged preserves callback zone', () {
       Zone innerZone;
       Zone runZone;
+      bool enabled;
 
       runZoned(() {
         innerZone = Zone.current;
         window.onSemanticsEnabledChanged = () {
           runZone = Zone.current;
+          enabled = window.semanticsEnabled;
         };
       });
 
       _updateSemanticsEnabled(window._semanticsEnabled);
       expect(runZone, isNotNull);
       expect(runZone, same(innerZone));
+      expect(enabled, isNotNull);
+      expect(enabled, equals(window._semanticsEnabled));
     });
 
     test('onSemanticsAction preserves callback zone', () {
       Zone innerZone;
       Zone runZone;
+      int action;
 
       runZoned(() {
         innerZone = Zone.current;
-        window.onSemanticsAction = (_, __) {
+        window.onSemanticsAction = (int value, _) {
           runZone = Zone.current;
+          action = value;
         };
       });
 
-      _dispatchSemanticsAction(0, 0);
+      _dispatchSemanticsAction(1234, 0);
       expect(runZone, isNotNull);
       expect(runZone, same(innerZone));
+      expect(action, equals(1234));
     });
 
     test('onPlatformMessage preserves callback zone', () {
       Zone innerZone;
       Zone runZone;
+      String name;
 
       runZoned(() {
         innerZone = Zone.current;
-        window.onPlatformMessage = (_, __, ___) {
+        window.onPlatformMessage = (String value, _, __) {
           runZone = Zone.current;
+          name = value;
         };
       });
 
-      _dispatchPlatformMessage(null, null, null);
+      _dispatchPlatformMessage('testName', null, null);
       expect(runZone, isNotNull);
       expect(runZone, same(innerZone));
+      expect(name, equals('testName'));
+    });
+
+    test('onTextScaleFactorChanged preserves callback zone', () {
+      Zone innerZone;
+      Zone runZone;
+      double textScaleFactor;
+
+      runZoned(() {
+        innerZone = Zone.current;
+        window.onTextScaleFactorChanged = () {
+          runZone = Zone.current;
+          textScaleFactor = window.textScaleFactor;
+        };
+      });
+
+      window.onTextScaleFactorChanged();
+      _updateTextScaleFactor(0.5);
+      expect(runZone, isNotNull);
+      expect(runZone, same(innerZone));
+      expect(textScaleFactor, equals(0.5));
     });
   });
 }