Setup default font manager after engine created, to improve startup performance.

Author: scutlight

lib/ui/text/font_collection.cc

@@ -47,8 +47,6 @@ void _LoadFontFromList(Dart_NativeArguments args) {
 
 FontCollection::FontCollection()
     : collection_(std::make_shared<txt::FontCollection>()) {
-  collection_->SetupDefaultFontManager();
-
   dynamic_font_manager_ = sk_make_sp<txt::DynamicFontManager>();
   collection_->SetDynamicFontManager(dynamic_font_manager_);
 }
@@ -68,6 +66,10 @@ std::shared_ptr<txt::FontCollection> FontCollection::GetFontCollection() const {
   return collection_;
 }
 
+void FontCollection::SetupDefaultFontManager() {
+  collection_->SetupDefaultFontManager();
+}
+
 void FontCollection::RegisterFonts(
     std::shared_ptr<AssetManager> asset_manager) {
   std::unique_ptr<fml::Mapping> manifest_mapping =

lib/ui/text/font_collection.h

@@ -29,6 +29,8 @@ class FontCollection {
 
   std::shared_ptr<txt::FontCollection> GetFontCollection() const;
 
+  void SetupDefaultFontManager();
+
   void RegisterFonts(std::shared_ptr<AssetManager> asset_manager);
 
   void RegisterTestFonts();

shell/common/engine.cc

@@ -90,6 +90,11 @@ fml::WeakPtr<Engine> Engine::GetWeakPtr() const {
   return weak_factory_.GetWeakPtr();
 }
 
+void Engine::SetupDefaultFontManager() {
+  TRACE_EVENT0("flutter", "Engine::SetupDefaultFontManager");
+  font_collection_.SetupDefaultFontManager();
+}
+
 bool Engine::UpdateAssetManager(
     std::shared_ptr<AssetManager> new_asset_manager) {
   if (asset_manager_ == new_asset_manager) {

shell/common/engine.h

@@ -363,6 +363,13 @@ class Engine final : public RuntimeDelegate, PointerDataDispatcher::Delegate {
   ///
   [[nodiscard]] bool Restart(RunConfiguration configuration);
 
+  //----------------------------------------------------------------------------
+  /// @brief      Setup default font manager according to specific platform.
+  ///
+  /// @attention  This operation calls `SkFontMgr::RefDefault` which is
+  ///             time-consuming except running at linux and windows.
+  void SetupDefaultFontManager();
+
   //----------------------------------------------------------------------------
   /// @brief      Updates the asset manager referenced by the root isolate of a
   ///             Flutter application. This happens implicitly in the call to

shell/common/shell.cc

@@ -542,6 +542,14 @@ bool Shell::Setup(std::unique_ptr<PlatformView> platform_view,
   weak_rasterizer_ = rasterizer_->GetWeakPtr();
   weak_platform_view_ = platform_view_->GetWeakPtr();
 
+  // Setup the time-consuming default font manager right after engine created.
+  fml::TaskRunner::RunNowOrPostTask(task_runners_.GetUITaskRunner(),
+                                    [engine = weak_engine_] {
+                                      if (engine) {
+                                        engine->SetupDefaultFontManager();
+                                      }
+                                    });
+
   is_setup_ = true;
 
   vm_->GetServiceProtocol()->AddHandler(this, GetServiceProtocolDescription());