Remove RunLoop from Windows template (#79969)

packages/flutter_tools/templates/app/windows.tmpl/runner/CMakeLists.txt

@@ -4,7 +4,6 @@ project(runner LANGUAGES CXX)
 add_executable(${BINARY_NAME} WIN32
   "flutter_window.cpp"
   "main.cpp"
-  "run_loop.cpp"
   "utils.cpp"
   "win32_window.cpp"
   "${FLUTTER_MANAGED_DIR}/generated_plugin_registrant.cc"

packages/flutter_tools/templates/app/windows.tmpl/runner/flutter_window.cpp

@@ -4,9 +4,8 @@
 
 #include "flutter/generated_plugin_registrant.h"
 
-FlutterWindow::FlutterWindow(RunLoop* run_loop,
-                             const flutter::DartProject& project)
-    : run_loop_(run_loop), project_(project) {}
+FlutterWindow::FlutterWindow(const flutter::DartProject& project)
+    : project_(project) {}
 
 FlutterWindow::~FlutterWindow() {}
 
@@ -26,14 +25,12 @@ bool FlutterWindow::OnCreate() {
     return false;
   }
   RegisterPlugins(flutter_controller_->engine());
-  run_loop_->RegisterFlutterInstance(flutter_controller_->engine());
   SetChildContent(flutter_controller_->view()->GetNativeWindow());
   return true;
 }
 
 void FlutterWindow::OnDestroy() {
   if (flutter_controller_) {
-    run_loop_->UnregisterFlutterInstance(flutter_controller_->engine());
     flutter_controller_ = nullptr;
   }
 

packages/flutter_tools/templates/app/windows.tmpl/runner/flutter_window.h

@@ -6,16 +6,13 @@
 
 #include <memory>
 
-#include "run_loop.h"
 #include "win32_window.h"
 
 // A window that does nothing but host a Flutter view.
 class FlutterWindow : public Win32Window {
  public:
-  // Creates a new FlutterWindow driven by the |run_loop|, hosting a
-  // Flutter view running |project|.
-  explicit FlutterWindow(RunLoop* run_loop,
-                         const flutter::DartProject& project);
+  // Creates a new FlutterWindow hosting a Flutter view running |project|.
+  explicit FlutterWindow(const flutter::DartProject& project);
   virtual ~FlutterWindow();
 
  protected:
@@ -26,9 +23,6 @@ class FlutterWindow : public Win32Window {
                          LPARAM const lparam) noexcept override;
 
  private:
-  // The run loop driving events for this window.
-  RunLoop* run_loop_;
-
   // The project to run.
   flutter::DartProject project_;
 

packages/flutter_tools/templates/app/windows.tmpl/runner/main.cpp.tmpl

@@ -3,7 +3,6 @@
 #include <windows.h>
 
 #include "flutter_window.h"
-#include "run_loop.h"
 #include "utils.h"
 
 int APIENTRY wWinMain(_In_ HINSTANCE instance, _In_opt_ HINSTANCE prev,
@@ -18,8 +17,6 @@ int APIENTRY wWinMain(_In_ HINSTANCE instance, _In_opt_ HINSTANCE prev,
   // plugins.
   ::CoInitializeEx(nullptr, COINIT_APARTMENTTHREADED);
 
-  RunLoop run_loop;
-
   flutter::DartProject project(L"data");
 
   std::vector<std::string> command_line_arguments =
@@ -27,7 +24,7 @@ int APIENTRY wWinMain(_In_ HINSTANCE instance, _In_opt_ HINSTANCE prev,
 
   project.set_dart_entrypoint_arguments(std::move(command_line_arguments));
 
-  FlutterWindow window(&run_loop, project);
+  FlutterWindow window(project);
   Win32Window::Point origin(10, 10);
   Win32Window::Size size(1280, 720);
   if (!window.CreateAndShow(L"{{projectName}}", origin, size)) {
@@ -35,7 +32,11 @@ int APIENTRY wWinMain(_In_ HINSTANCE instance, _In_opt_ HINSTANCE prev,
   }
   window.SetQuitOnClose(true);
 
-  run_loop.Run();
+  ::MSG msg;
+  while (::GetMessage(&msg, nullptr, 0, 0)) {
+    ::TranslateMessage(&msg);
+    ::DispatchMessage(&msg);
+  }
 
   ::CoUninitialize();
   return EXIT_SUCCESS;

packages/flutter_tools/templates/app/windows.tmpl/runner/run_loop.cpp

-#include "run_loop.h"
-
-#include <windows.h>
-
-#include <algorithm>
-
-RunLoop::RunLoop() {}
-
-RunLoop::~RunLoop() {}
-
-void RunLoop::Run() {
-  bool keep_running = true;
-  TimePoint next_flutter_event_time = TimePoint::clock::now();
-  while (keep_running) {
-    std::chrono::nanoseconds wait_duration =
-        std::max(std::chrono::nanoseconds(0),
-                 next_flutter_event_time - TimePoint::clock::now());
-    ::MsgWaitForMultipleObjects(
-        0, nullptr, FALSE, static_cast<DWORD>(wait_duration.count() / 1000),
-        QS_ALLINPUT);
-    bool processed_events = false;
-    MSG message;
-    // All pending Windows messages must be processed; MsgWaitForMultipleObjects
-    // won't return again for items left in the queue after PeekMessage.
-    while (::PeekMessage(&message, nullptr, 0, 0, PM_REMOVE)) {
-      processed_events = true;
-      if (message.message == WM_QUIT) {
-        keep_running = false;
-        break;
-      }
-      ::TranslateMessage(&message);
-      ::DispatchMessage(&message);
-      // Allow Flutter to process messages each time a Windows message is
-      // processed, to prevent starvation.
-      next_flutter_event_time =
-          std::min(next_flutter_event_time, ProcessFlutterMessages());
-    }
-    // If the PeekMessage loop didn't run, process Flutter messages.
-    if (!processed_events) {
-      next_flutter_event_time =
-          std::min(next_flutter_event_time, ProcessFlutterMessages());
-    }
-  }
-}
-
-void RunLoop::RegisterFlutterInstance(
-    flutter::FlutterEngine* flutter_instance) {
-  flutter_instances_.insert(flutter_instance);
-}
-
-void RunLoop::UnregisterFlutterInstance(
-    flutter::FlutterEngine* flutter_instance) {
-  flutter_instances_.erase(flutter_instance);
-}
-
-RunLoop::TimePoint RunLoop::ProcessFlutterMessages() {
-  TimePoint next_event_time = TimePoint::max();
-  for (auto instance : flutter_instances_) {
-    std::chrono::nanoseconds wait_duration = instance->ProcessMessages();
-    if (wait_duration != std::chrono::nanoseconds::max()) {
-      next_event_time =
-          std::min(next_event_time, TimePoint::clock::now() + wait_duration);
-    }
-  }
-  return next_event_time;
-}

packages/flutter_tools/templates/app/windows.tmpl/runner/run_loop.h

-#ifndef RUNNER_RUN_LOOP_H_
-#define RUNNER_RUN_LOOP_H_
-
-#include <flutter/flutter_engine.h>
-
-#include <chrono>
-#include <set>
-
-// A runloop that will service events for Flutter instances as well
-// as native messages.
-class RunLoop {
- public:
-  RunLoop();
-  ~RunLoop();
-
-  // Prevent copying
-  RunLoop(RunLoop const&) = delete;
-  RunLoop& operator=(RunLoop const&) = delete;
-
-  // Runs the run loop until the application quits.
-  void Run();
-
-  // Registers the given Flutter instance for event servicing.
-  void RegisterFlutterInstance(
-      flutter::FlutterEngine* flutter_instance);
-
-  // Unregisters the given Flutter instance from event servicing.
-  void UnregisterFlutterInstance(
-      flutter::FlutterEngine* flutter_instance);
-
- private:
-  using TimePoint = std::chrono::steady_clock::time_point;
-
-  // Processes all currently pending messages for registered Flutter instances.
-  TimePoint ProcessFlutterMessages();
-
-  std::set<flutter::FlutterEngine*> flutter_instances_;
-};
-
-#endif  // RUNNER_RUN_LOOP_H_