Implemented isolate platform channels for desktop / embedders

Author: gaaclarke

lib/ui/platform_dispatcher.dart

@@ -584,7 +584,7 @@ class PlatformDispatcher {
   /// [token]. This is required if platform channels are to be used on a
   /// background isolate.
   void registerBackgroundIsolate(RootIsolateToken token) {
-    if (!Platform.isIOS) {
+    if (!(Platform.isIOS || Platform.isMacOS)) {
       // Issue: https://github.com/flutter/flutter/issues/13937
       throw UnimplementedError("Platform doesn't yet support platform channels on background isolates.");
     }

shell/platform/embedder/platform_view_embedder.cc

@@ -4,8 +4,42 @@
 
 #include "flutter/shell/platform/embedder/platform_view_embedder.h"
 
+#include "flutter/fml/make_copyable.h"
+
 namespace flutter {
 
+class PlatformViewEmbedder::EmbedderPlatformMessageHandler
+    : public PlatformMessageHandler {
+ public:
+  EmbedderPlatformMessageHandler(
+      PlatformViewEmbedder* parent,
+      fml::RefPtr<fml::TaskRunner> platform_task_runner)
+      : parent_(std::make_shared<PlatformViewEmbedder*>(parent)),
+        platform_task_runner_(platform_task_runner) {}
+
+  virtual void HandlePlatformMessage(std::unique_ptr<PlatformMessage> message) {
+    platform_task_runner_->PostTask(fml::MakeCopyable(
+        [parent = parent_, message = std::move(message)]() mutable {
+          if (*parent) {
+            (*parent)->HandlePlatformMessage(std::move(message));
+          } else {
+            FML_DLOG(WARNING)
+                << "Dropping message on channel " << message->channel();
+          }
+        }));
+  }
+  virtual void InvokePlatformMessageResponseCallback(
+      int response_id,
+      std::unique_ptr<fml::Mapping> mapping) {}
+  virtual void InvokePlatformMessageEmptyResponseCallback(int response_id) {}
+
+  void ClearParent() { parent_.reset(); }
+
+ private:
+  std::shared_ptr<PlatformViewEmbedder*> parent_;
+  fml::RefPtr<fml::TaskRunner> platform_task_runner_;
+};
+
 PlatformViewEmbedder::PlatformViewEmbedder(
     PlatformView::Delegate& delegate,
     flutter::TaskRunners task_runners,
@@ -17,7 +51,10 @@ PlatformViewEmbedder::PlatformViewEmbedder(
       embedder_surface_(
           std::make_unique<EmbedderSurfaceSoftware>(software_dispatch_table,
                                                     external_view_embedder_)),
-      platform_dispatch_table_(platform_dispatch_table) {}
+      platform_dispatch_table_(platform_dispatch_table) {
+  platform_message_handler_ = std::make_shared<EmbedderPlatformMessageHandler>(
+      this, task_runners_.GetPlatformTaskRunner());
+}
 
 #ifdef SHELL_ENABLE_GL
 PlatformViewEmbedder::PlatformViewEmbedder(
@@ -33,7 +70,10 @@ PlatformViewEmbedder::PlatformViewEmbedder(
           std::make_unique<EmbedderSurfaceGL>(gl_dispatch_table,
                                               fbo_reset_after_present,
                                               external_view_embedder_)),
-      platform_dispatch_table_(platform_dispatch_table) {}
+      platform_dispatch_table_(platform_dispatch_table) {
+  platform_message_handler_ = std::make_shared<EmbedderPlatformMessageHandler>(
+      this, task_runners_.GetPlatformTaskRunner());
+}
 #endif
 
 #ifdef SHELL_ENABLE_METAL
@@ -46,7 +86,10 @@ PlatformViewEmbedder::PlatformViewEmbedder(
     : PlatformView(delegate, std::move(task_runners)),
       external_view_embedder_(external_view_embedder),
       embedder_surface_(std::move(embedder_surface)),
-      platform_dispatch_table_(platform_dispatch_table) {}
+      platform_dispatch_table_(platform_dispatch_table) {
+  platform_message_handler_ = std::make_shared<EmbedderPlatformMessageHandler>(
+      this, task_runners_.GetPlatformTaskRunner());
+}
 #endif
 
 #ifdef SHELL_ENABLE_VULKAN
@@ -59,10 +102,15 @@ PlatformViewEmbedder::PlatformViewEmbedder(
     : PlatformView(delegate, std::move(task_runners)),
       external_view_embedder_(external_view_embedder),
       embedder_surface_(std::move(embedder_surface)),
-      platform_dispatch_table_(platform_dispatch_table) {}
+      platform_dispatch_table_(platform_dispatch_table) {
+  platform_message_handler_ = std::make_shared<EmbedderPlatformMessageHandler>(
+      this, task_runners_.GetPlatformTaskRunner());
+}
 #endif
 
-PlatformViewEmbedder::~PlatformViewEmbedder() = default;
+PlatformViewEmbedder::~PlatformViewEmbedder() {
+  platform_message_handler_->ClearParent();
+}
 
 void PlatformViewEmbedder::UpdateSemantics(
     flutter::SemanticsNodeUpdates update,
@@ -146,4 +194,9 @@ void PlatformViewEmbedder::OnPreEngineRestart() const {
   }
 }
 
+std::shared_ptr<PlatformMessageHandler>
+PlatformViewEmbedder::GetPlatformMessageHandler() const {
+  return platform_message_handler_;
+}
+
 }  // namespace flutter

shell/platform/embedder/platform_view_embedder.h

@@ -101,8 +101,10 @@ class PlatformViewEmbedder final : public PlatformView {
   void HandlePlatformMessage(std::unique_ptr<PlatformMessage> message) override;
 
  private:
+  class EmbedderPlatformMessageHandler;
   std::shared_ptr<EmbedderExternalViewEmbedder> external_view_embedder_;
   std::unique_ptr<EmbedderSurface> embedder_surface_;
+  std::shared_ptr<EmbedderPlatformMessageHandler> platform_message_handler_;
   PlatformDispatchTable platform_dispatch_table_;
 
   // |PlatformView|
@@ -124,6 +126,10 @@ class PlatformViewEmbedder final : public PlatformView {
   std::unique_ptr<std::vector<std::string>> ComputePlatformResolvedLocales(
       const std::vector<std::string>& supported_locale_data) override;
 
+  // |PlatformView|
+  std::shared_ptr<PlatformMessageHandler> GetPlatformMessageHandler()
+      const override;
+
   FML_DISALLOW_COPY_AND_ASSIGN(PlatformViewEmbedder);
 };