Revert "[Windows] Enable merged platform and UI thread by default" (flutter#167420)

This reverts commit afdc861.

See: flutter#167418

Author: loic-sharma

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

@@ -299,12 +299,11 @@ bool FlutterWindowsEngine::Run(std::string_view entrypoint) {
   custom_task_runners.thread_priority_setter =
       &WindowsPlatformThreadPrioritySetter;
 
-  if (project_->ui_thread_policy() !=
-      FlutterUIThreadPolicy::RunOnSeparateThread) {
+  if (project_->ui_thread_policy() ==
+      FlutterUIThreadPolicy::RunOnPlatformThread) {
+    FML_LOG(WARNING)
+        << "Running with merged platform and UI thread. Experimental.";
     custom_task_runners.ui_task_runner = &platform_task_runner;
-  } else {
-    FML_LOG(WARNING) << "Running with unmerged platform and UI threads. This "
-                        "will be removed in future.";
   }
 
   FlutterProjectArgs args = {};

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

@@ -131,23 +131,20 @@ TEST_F(WindowsTest, LaunchHeadlessEngine) {
   ASSERT_NE(engine, nullptr);
 
   std::string view_ids;
-  bool signaled = false;
+  fml::AutoResetWaitableEvent latch;
   context.AddNativeFunction(
       "SignalStringValue", CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
         auto handle = Dart_GetNativeArgument(args, 0);
         ASSERT_FALSE(Dart_IsError(handle));
         view_ids = tonic::DartConverter<std::string>::FromDart(handle);
-        signaled = true;
+        latch.Signal();
       }));
 
   ViewControllerPtr controller{builder.Run()};
   ASSERT_NE(controller, nullptr);
 
-  while (!signaled) {
-    PumpMessage();
-  }
-
   // Verify a headless app has the implicit view.
+  latch.Wait();
   EXPECT_EQ(view_ids, "View IDs: [0]");
 }
 
@@ -217,18 +214,16 @@ TEST_F(WindowsTest, VerifyNativeFunction) {
   WindowsConfigBuilder builder(context);
   builder.SetDartEntrypoint("verifyNativeFunction");
 
-  bool signaled = false;
+  fml::AutoResetWaitableEvent latch;
   auto native_entry =
-      CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) { signaled = true; });
+      CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) { latch.Signal(); });
   context.AddNativeFunction("Signal", native_entry);
 
   ViewControllerPtr controller{builder.Run()};
   ASSERT_NE(controller, nullptr);
 
   // Wait until signal has been called.
-  while (!signaled) {
-    PumpMessage();
-  }
+  latch.Wait();
 }
 
 // Verify that native functions that pass parameters can be registered and
@@ -239,21 +234,19 @@ TEST_F(WindowsTest, VerifyNativeFunctionWithParameters) {
   builder.SetDartEntrypoint("verifyNativeFunctionWithParameters");
 
   bool bool_value = false;
-  bool signaled = false;
+  fml::AutoResetWaitableEvent latch;
   auto native_entry = CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
     auto handle = Dart_GetNativeBooleanArgument(args, 0, &bool_value);
     ASSERT_FALSE(Dart_IsError(handle));
-    signaled = true;
+    latch.Signal();
   });
   context.AddNativeFunction("SignalBoolValue", native_entry);
 
   ViewControllerPtr controller{builder.Run()};
   ASSERT_NE(controller, nullptr);
 
   // Wait until signalBoolValue has been called.
-  while (!signaled) {
-    PumpMessage();
-  }
+  latch.Wait();
   EXPECT_TRUE(bool_value);
 }
 
@@ -264,22 +257,20 @@ TEST_F(WindowsTest, PlatformExecutable) {
   builder.SetDartEntrypoint("readPlatformExecutable");
 
   std::string executable_name;
-  bool signaled = false;
+  fml::AutoResetWaitableEvent latch;
   auto native_entry = CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
     auto handle = Dart_GetNativeArgument(args, 0);
     ASSERT_FALSE(Dart_IsError(handle));
     executable_name = tonic::DartConverter<std::string>::FromDart(handle);
-    signaled = true;
+    latch.Signal();
   });
   context.AddNativeFunction("SignalStringValue", native_entry);
 
   ViewControllerPtr controller{builder.Run()};
   ASSERT_NE(controller, nullptr);
 
   // Wait until signalStringValue has been called.
-  while (!signaled) {
-    PumpMessage();
-  }
+  latch.Wait();
   EXPECT_EQ(executable_name, "flutter_windows_unittests.exe");
 }
 
@@ -291,28 +282,26 @@ TEST_F(WindowsTest, VerifyNativeFunctionWithReturn) {
   builder.SetDartEntrypoint("verifyNativeFunctionWithReturn");
 
   bool bool_value_to_return = true;
-  int count = 2;
+  fml::CountDownLatch latch(2);
   auto bool_return_entry = CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
     Dart_SetBooleanReturnValue(args, bool_value_to_return);
-    --count;
+    latch.CountDown();
   });
   context.AddNativeFunction("SignalBoolReturn", bool_return_entry);
 
   bool bool_value_passed = false;
   auto bool_pass_entry = CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
     auto handle = Dart_GetNativeBooleanArgument(args, 0, &bool_value_passed);
     ASSERT_FALSE(Dart_IsError(handle));
-    --count;
+    latch.CountDown();
   });
   context.AddNativeFunction("SignalBoolValue", bool_pass_entry);
 
   ViewControllerPtr controller{builder.Run()};
   ASSERT_NE(controller, nullptr);
 
   // Wait until signalBoolReturn and signalBoolValue have been called.
-  while (count > 0) {
-    PumpMessage();
-  }
+  latch.Wait();
   EXPECT_TRUE(bool_value_passed);
 }
 
@@ -625,10 +614,10 @@ TEST_F(WindowsTest, AddRemoveView) {
   WindowsConfigBuilder builder(context);
   builder.SetDartEntrypoint("onMetricsChangedSignalViewIds");
 
-  bool ready = false;
+  fml::AutoResetWaitableEvent ready_latch;
   context.AddNativeFunction(
-      "Signal",
-      CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) { ready = true; }));
+      "Signal", CREATE_NATIVE_ENTRY(
+                    [&](Dart_NativeArguments args) { ready_latch.Signal(); }));
 
   context.AddNativeFunction(
       "SignalStringValue", CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
@@ -643,9 +632,7 @@ TEST_F(WindowsTest, AddRemoveView) {
   ViewControllerPtr first_controller{builder.Run()};
   ASSERT_NE(first_controller, nullptr);
 
-  while (!ready) {
-    PumpMessage();
-  }
+  ready_latch.Wait();
 
   // Create a second view.
   FlutterDesktopEngineRef engine =
@@ -683,6 +670,7 @@ TEST_F(WindowsTest, EngineId) {
   WindowsConfigBuilder builder(context);
   builder.SetDartEntrypoint("testEngineId");
 
+  fml::AutoResetWaitableEvent latch;
   std::optional<int64_t> engineId;
   context.AddNativeFunction(
       "NotifyEngineId", CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
@@ -691,15 +679,17 @@ TEST_F(WindowsTest, EngineId) {
           const auto handle = tonic::DartConverter<int64_t>::FromDart(argument);
           engineId = handle;
         }
+        latch.Signal();
       }));
   // Create the implicit view.
   ViewControllerPtr first_controller{builder.Run()};
   ASSERT_NE(first_controller, nullptr);
 
-  while (!engineId.has_value()) {
-    PumpMessage();
+  latch.Wait();
+  EXPECT_TRUE(engineId.has_value());
+  if (!engineId.has_value()) {
+    return;
   }
-
   auto engine = FlutterDesktopViewControllerGetEngine(first_controller.get());
   EXPECT_EQ(engine, FlutterDesktopEngineForId(*engineId));
 }