Add system font change listener for windows (flutter/engine#12276)

* Add windows font change logic

* update

* fix comment

engine/src/flutter/ci/licenses_golden/licenses_flutter

@@ -1036,6 +1036,7 @@ FILE: ../../../flutter/third_party/txt/src/txt/platform_android.cc
 FILE: ../../../flutter/third_party/txt/src/txt/platform_fuchsia.cc
 FILE: ../../../flutter/third_party/txt/src/txt/platform_linux.cc
 FILE: ../../../flutter/third_party/txt/src/txt/platform_mac.mm
+FILE: ../../../flutter/third_party/txt/src/txt/platform_windows.cc
 FILE: ../../../flutter/vulkan/vulkan_application.cc
 FILE: ../../../flutter/vulkan/vulkan_application.h
 FILE: ../../../flutter/vulkan/vulkan_backbuffer.cc

engine/src/flutter/shell/common/shell.cc

@@ -26,6 +26,8 @@
 #include "flutter/shell/common/skia_event_tracer_impl.h"
 #include "flutter/shell/common/switches.h"
 #include "flutter/shell/common/vsync_waiter.h"
+#include "rapidjson/stringbuffer.h"
+#include "rapidjson/writer.h"
 #include "third_party/dart/runtime/include/dart_tools_api.h"
 #include "third_party/skia/include/core/SkGraphics.h"
 #include "third_party/tonic/common/log.h"
@@ -33,6 +35,9 @@
 namespace flutter {
 
 constexpr char kSkiaChannel[] = "flutter/skia";
+constexpr char kSystemChannel[] = "flutter/system";
+constexpr char kTypeKey[] = "type";
+constexpr char kFontChange[] = "fontsChange";
 
 std::unique_ptr<Shell> Shell::CreateShellOnPlatformThread(
     DartVMRef vm,
@@ -1351,4 +1356,35 @@ fml::Status Shell::WaitForFirstFrame(fml::TimeDelta timeout) {
   }
 }
 
+bool Shell::ReloadSystemFonts() {
+  FML_DCHECK(is_setup_);
+  FML_DCHECK(task_runners_.GetPlatformTaskRunner()->RunsTasksOnCurrentThread());
+
+  if (!engine_) {
+    return false;
+  }
+  engine_->GetFontCollection().GetFontCollection()->SetupDefaultFontManager();
+  engine_->GetFontCollection().GetFontCollection()->ClearFontFamilyCache();
+  // After system fonts are reloaded, we send a system channel message
+  // to notify flutter framework.
+  rapidjson::Document document;
+  document.SetObject();
+  auto& allocator = document.GetAllocator();
+  rapidjson::Value message_value;
+  message_value.SetString(kFontChange, allocator);
+  document.AddMember(kTypeKey, message_value, allocator);
+
+  rapidjson::StringBuffer buffer;
+  rapidjson::Writer<rapidjson::StringBuffer> writer(buffer);
+  document.Accept(writer);
+  std::string message = buffer.GetString();
+  fml::RefPtr<PlatformMessage> fontsChangeMessage =
+      fml::MakeRefCounted<flutter::PlatformMessage>(
+          kSystemChannel, std::vector<uint8_t>(message.begin(), message.end()),
+          nullptr);
+
+  OnPlatformViewDispatchPlatformMessage(fontsChangeMessage);
+  return true;
+}
+
 }  // namespace flutter

engine/src/flutter/shell/common/shell.h

@@ -284,6 +284,16 @@ class Shell final : public PlatformView::Delegate,
   ///
   fml::Status WaitForFirstFrame(fml::TimeDelta timeout);
 
+  //----------------------------------------------------------------------------
+  /// @brief      Used by embedders to reload the system fonts in
+  /// FontCollection.
+  ///             It also clears the cached font families and send system
+  ///             channel message to framework to rebuild affected widgets.
+  ///
+  /// @return     Returns if shell reloads system fonts successfully.
+  ///
+  bool ReloadSystemFonts();
+
   //----------------------------------------------------------------------------
   /// @brief      Used by embedders to get the last error from the Dart UI
   ///             Isolate, if one exists.

engine/src/flutter/shell/common/shell_test.cc

@@ -144,6 +144,11 @@ bool ShellTest::GetNeedsReportTimings(Shell* shell) {
   return shell->needs_report_timings_;
 }
 
+std::shared_ptr<txt::FontCollection> ShellTest::GetFontCollection(
+    Shell* shell) {
+  return shell->weak_engine_->GetFontCollection().GetFontCollection();
+}
+
 Settings ShellTest::CreateSettingsForFixture() {
   Settings settings;
   settings.leak_vm = false;

engine/src/flutter/shell/common/shell_test.h

@@ -51,6 +51,8 @@ class ShellTest : public ThreadTest {
   static bool GetNeedsReportTimings(Shell* shell);
   static void SetNeedsReportTimings(Shell* shell, bool value);
 
+  std::shared_ptr<txt::FontCollection> GetFontCollection(Shell* shell);
+
   // Do not assert |UnreportedTimingsCount| to be positive in any tests.
   // Otherwise those tests will be flaky as the clearing of unreported timings
   // is unpredictive.

engine/src/flutter/shell/common/shell_unittests.cc

@@ -519,6 +519,36 @@ TEST_F(ShellTest, ReportTimingsIsCalledImmediatelyAfterTheFirstFrame) {
   ASSERT_EQ(timestamps.size(), FrameTiming::kCount);
 }
 
+TEST_F(ShellTest, ReloadSystemFonts) {
+  auto settings = CreateSettingsForFixture();
+
+  fml::MessageLoop::EnsureInitializedForCurrentThread();
+  auto task_runner = fml::MessageLoop::GetCurrent().GetTaskRunner();
+  TaskRunners task_runners("test", task_runner, task_runner, task_runner,
+                           task_runner);
+  auto shell = CreateShell(std::move(settings), std::move(task_runners));
+
+  auto fontCollection = GetFontCollection(shell.get());
+  std::vector<std::string> families(1, "Robotofake");
+  auto font =
+      fontCollection->GetMinikinFontCollectionForFamilies(families, "en");
+  if (font == nullptr) {
+    // The system does not have default font. Aborts this test.
+    return;
+  }
+  unsigned int id = font->getId();
+  // The result should be cached.
+  font = fontCollection->GetMinikinFontCollectionForFamilies(families, "en");
+  ASSERT_EQ(font->getId(), id);
+  bool result = shell->ReloadSystemFonts();
+
+  // The cache is cleared, and FontCollection will be assigned a new id.
+  font = fontCollection->GetMinikinFontCollectionForFamilies(families, "en");
+  ASSERT_NE(font->getId(), id);
+  ASSERT_TRUE(result);
+  shell.reset();
+}
+
 TEST_F(ShellTest, WaitForFirstFrame) {
   auto settings = CreateSettingsForFixture();
   std::unique_ptr<Shell> shell = CreateShell(settings);

engine/src/flutter/shell/platform/embedder/embedder.cc

@@ -1279,6 +1279,22 @@ FlutterEngineResult FlutterEngineOnVsync(FLUTTER_API_SYMBOL(FlutterEngine)
   return kSuccess;
 }
 
+FlutterEngineResult FlutterEngineReloadSystemFonts(
+    FLUTTER_API_SYMBOL(FlutterEngine) engine) {
+  if (engine == nullptr) {
+    return LOG_EMBEDDER_ERROR(kInvalidArguments);
+  }
+
+  TRACE_EVENT0("flutter", "FlutterEngineReloadSystemFonts");
+
+  if (!reinterpret_cast<flutter::EmbedderEngine*>(engine)
+           ->ReloadSystemFonts()) {
+    return LOG_EMBEDDER_ERROR(kInternalInconsistency);
+  }
+
+  return kSuccess;
+}
+
 void FlutterEngineTraceEventDurationBegin(const char* name) {
   fml::tracing::TraceEvent0("flutter", name);
 }

engine/src/flutter/shell/platform/embedder/embedder.h

@@ -1200,6 +1200,17 @@ FlutterEngineResult FlutterEngineOnVsync(FLUTTER_API_SYMBOL(FlutterEngine)
                                          uint64_t frame_start_time_nanos,
                                          uint64_t frame_target_time_nanos);
 
+//------------------------------------------------------------------------------
+/// @brief      Reloads the system fonts in engine.
+///
+/// @param[in]  engine.                  A running engine instance.
+///
+/// @return     The result of the call.
+///
+FLUTTER_EXPORT
+FlutterEngineResult FlutterEngineReloadSystemFonts(
+    FLUTTER_API_SYMBOL(FlutterEngine) engine);
+
 //------------------------------------------------------------------------------
 /// @brief      A profiling utility. Logs a trace duration begin event to the
 ///             timeline. If the timeline is unavailable or disabled, this has

engine/src/flutter/shell/platform/embedder/embedder_engine.cc

@@ -186,6 +186,10 @@ bool EmbedderEngine::OnVsyncEvent(intptr_t baton,
                                               frame_target_time);
 }
 
+bool EmbedderEngine::ReloadSystemFonts() {
+  return shell_->ReloadSystemFonts();
+}
+
 bool EmbedderEngine::PostRenderThreadTask(fml::closure task) {
   if (!IsValid()) {
     return false;

engine/src/flutter/shell/platform/embedder/embedder_engine.h

@@ -67,6 +67,8 @@ class EmbedderEngine {
                     fml::TimePoint frame_start_time,
                     fml::TimePoint frame_target_time);
 
+  bool ReloadSystemFonts();
+
   bool PostRenderThreadTask(fml::closure task);
 
   bool RunTask(const FlutterTask* task);

engine/src/flutter/shell/platform/embedder/tests/embedder_unittests.cc

@@ -235,6 +235,17 @@ TEST(EmbedderTestNoFixture, CanGetCurrentTimeInNanoseconds) {
   ASSERT_LT((point2 - point1), fml::TimeDelta::FromMilliseconds(1));
 }
 
+TEST_F(EmbedderTest, CanReloadSystemFonts) {
+  auto& context = GetEmbedderContext();
+  EmbedderConfigBuilder builder(context);
+  builder.SetSoftwareRendererConfig();
+  auto engine = builder.LaunchEngine();
+  ASSERT_TRUE(engine.is_valid());
+
+  auto result = FlutterEngineReloadSystemFonts(engine.get());
+  ASSERT_EQ(result, kSuccess);
+}
+
 TEST_F(EmbedderTest, CanCreateOpenGLRenderingEngine) {
   EmbedderConfigBuilder builder(GetEmbedderContext());
   builder.SetOpenGLRendererConfig(SkISize::Make(1, 1));

engine/src/flutter/shell/platform/windows/win32_flutter_window.cc

@@ -147,6 +147,13 @@ void Win32FlutterWindow::OnClose() {
   messageloop_running_ = false;
 }
 
+void Win32FlutterWindow::OnFontChange() {
+  if (engine_ == nullptr) {
+    return;
+  }
+  FlutterEngineReloadSystemFonts(engine_);
+}
+
 // Sends new size information to FlutterEngine.
 void Win32FlutterWindow::SendWindowMetrics() {
   if (engine_ == nullptr) {

engine/src/flutter/shell/platform/windows/win32_flutter_window.h

@@ -65,6 +65,9 @@ class Win32FlutterWindow : public Win32Window {
   // |Win32Window|
   void OnClose();
 
+  // |Win32Window|
+  void OnFontChange() override;
+
   // Configures the window instance with an instance of a running Flutter engine
   // returning a configured FlutterDesktopWindowControllerRef.
   void SetState(FLUTTER_API_SYMBOL(FlutterEngine) state);

engine/src/flutter/shell/platform/windows/win32_window.cc

@@ -129,7 +129,9 @@ Win32Window::MessageHandler(HWND hwnd,
         current_height_ = height;
         window->HandleResize(width, height);
         break;
-
+      case WM_FONTCHANGE:
+        window->OnFontChange();
+        break;
       case WM_MOUSEMOVE:
         xPos = GET_X_LPARAM(lparam);
         yPos = GET_Y_LPARAM(lparam);

engine/src/flutter/shell/platform/windows/win32_window.h

@@ -97,9 +97,12 @@ class Win32Window {
   // Called when mouse scrollwheel input occurs.
   virtual void OnScroll(double delta_x, double delta_y) = 0;
 
-  // Called when the user closes the Windows
+  // Called when the user closes the Windows.
   virtual void OnClose() = 0;
 
+  // Called when the system font change.
+  virtual void OnFontChange() = 0;
+
   UINT GetCurrentDPI();
 
   UINT GetCurrentWidth();

engine/src/flutter/third_party/txt/BUILD.gn

@@ -160,6 +160,8 @@ source_set("txt") {
     sources += [ "src/txt/platform_linux.cc" ]
   } else if (is_fuchsia) {
     sources += [ "src/txt/platform_fuchsia.cc" ]
+  } else if (is_win) {
+    sources += [ "src/txt/platform_windows.cc" ]
   } else {
     sources += [ "src/txt/platform.cc" ]
   }

engine/src/flutter/third_party/txt/src/txt/platform_windows.cc

@@ -0,0 +1,18 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "third_party/skia/include/ports/SkTypeface_win.h"
+#include "txt/platform.h"
+
+namespace txt {
+
+std::string GetDefaultFontFamily() {
+  return "Arial";
+}
+
+sk_sp<SkFontMgr> GetDefaultFontManager() {
+  return SkFontMgr_New_DirectWrite();
+}
+
+}  // namespace txt