[Windows] Make the engine create the view (#50673)

This makes the Windows engine create views. Benefits:

1. This will allow the engine to assign IDs to views as it creates them. This will be added in a subsequent change
2. Previously views needed special logic to not crash if they were used before an engine was attached to them. Now, views are always attached to an engine.

Part of flutter/flutter#137267
Part of flutter/flutter#142845

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: loic-sharma

shell/platform/windows/accessibility_bridge_windows_unittests.cc

@@ -26,6 +26,7 @@ namespace flutter {
 namespace testing {
 
 namespace {
+using ::testing::NiceMock;
 
 // A structure representing a Win32 MSAA event targeting a specified node.
 struct MsaaEvent {
@@ -88,8 +89,9 @@ class AccessibilityBridgeWindowsSpy : public AccessibilityBridgeWindows {
 // AccessibilityBridgeWindowsSpy.
 class FlutterWindowsViewSpy : public FlutterWindowsView {
  public:
-  explicit FlutterWindowsViewSpy(std::unique_ptr<WindowBindingHandler> handler)
-      : FlutterWindowsView(std::move(handler)) {}
+  FlutterWindowsViewSpy(FlutterWindowsEngine* engine,
+                        std::unique_ptr<WindowBindingHandler> handler)
+      : FlutterWindowsView(engine, std::move(handler)) {}
 
  protected:
   virtual std::shared_ptr<AccessibilityBridgeWindows>
@@ -187,10 +189,10 @@ void ExpectWinEventFromAXEvent(int32_t node_id,
                                ui::AXEventGenerator::Event ax_event,
                                ax::mojom::Event expected_event) {
   auto engine = GetTestEngine();
-  auto window_binding_handler =
-      std::make_unique<::testing::NiceMock<MockWindowBindingHandler>>();
-  FlutterWindowsViewSpy view(std::move(window_binding_handler));
-  view.SetEngine(engine.get());
+  FlutterWindowsViewSpy view{
+      engine.get(), std::make_unique<NiceMock<MockWindowBindingHandler>>()};
+  EngineModifier modifier{engine.get()};
+  modifier.SetImplicitView(&view);
   view.OnUpdateSemanticsEnabled(true);
 
   auto bridge = GetAccessibilityBridgeSpy(view);
@@ -208,10 +210,10 @@ void ExpectWinEventFromAXEventOnFocusNode(int32_t node_id,
                                           ax::mojom::Event expected_event,
                                           int32_t focus_id) {
   auto engine = GetTestEngine();
-  auto window_binding_handler =
-      std::make_unique<::testing::NiceMock<MockWindowBindingHandler>>();
-  FlutterWindowsViewSpy view(std::move(window_binding_handler));
-  view.SetEngine(engine.get());
+  FlutterWindowsViewSpy view{
+      engine.get(), std::make_unique<NiceMock<MockWindowBindingHandler>>()};
+  EngineModifier modifier{engine.get()};
+  modifier.SetImplicitView(&view);
   view.OnUpdateSemanticsEnabled(true);
 
   auto bridge = GetAccessibilityBridgeSpy(view);
@@ -234,10 +236,10 @@ void ExpectWinEventFromAXEventOnFocusNode(int32_t node_id,
 
 TEST(AccessibilityBridgeWindows, GetParent) {
   auto engine = GetTestEngine();
-  auto window_binding_handler =
-      std::make_unique<::testing::NiceMock<MockWindowBindingHandler>>();
-  FlutterWindowsViewSpy view(std::move(window_binding_handler));
-  view.SetEngine(engine.get());
+  FlutterWindowsViewSpy view{
+      engine.get(), std::make_unique<NiceMock<MockWindowBindingHandler>>()};
+  EngineModifier modifier{engine.get()};
+  modifier.SetImplicitView(&view);
   view.OnUpdateSemanticsEnabled(true);
 
   auto bridge = view.accessibility_bridge().lock();
@@ -251,10 +253,10 @@ TEST(AccessibilityBridgeWindows, GetParent) {
 
 TEST(AccessibilityBridgeWindows, GetParentOnRootRetunsNullptr) {
   auto engine = GetTestEngine();
-  auto window_binding_handler =
-      std::make_unique<::testing::NiceMock<MockWindowBindingHandler>>();
-  FlutterWindowsViewSpy view(std::move(window_binding_handler));
-  view.SetEngine(engine.get());
+  FlutterWindowsViewSpy view{
+      engine.get(), std::make_unique<NiceMock<MockWindowBindingHandler>>()};
+  EngineModifier modifier{engine.get()};
+  modifier.SetImplicitView(&view);
   view.OnUpdateSemanticsEnabled(true);
 
   auto bridge = view.accessibility_bridge().lock();
@@ -266,17 +268,16 @@ TEST(AccessibilityBridgeWindows, GetParentOnRootRetunsNullptr) {
 
 TEST(AccessibilityBridgeWindows, DispatchAccessibilityAction) {
   auto engine = GetTestEngine();
-  auto window_binding_handler =
-      std::make_unique<::testing::NiceMock<MockWindowBindingHandler>>();
-  FlutterWindowsViewSpy view(std::move(window_binding_handler));
-  view.SetEngine(engine.get());
+  FlutterWindowsViewSpy view{
+      engine.get(), std::make_unique<NiceMock<MockWindowBindingHandler>>()};
+  EngineModifier modifier{engine.get()};
+  modifier.SetImplicitView(&view);
   view.OnUpdateSemanticsEnabled(true);
 
   auto bridge = view.accessibility_bridge().lock();
   PopulateAXTree(bridge);
 
   FlutterSemanticsAction actual_action = kFlutterSemanticsActionTap;
-  EngineModifier modifier(view.GetEngine());
   modifier.embedder_api().DispatchSemanticsAction = MOCK_ENGINE_PROC(
       DispatchSemanticsAction,
       ([&actual_action](FLUTTER_API_SYMBOL(FlutterEngine) engine, uint64_t id,
@@ -303,10 +304,10 @@ TEST(AccessibilityBridgeWindows, OnAccessibilityEventChildrenChanged) {
 
 TEST(AccessibilityBridgeWindows, OnAccessibilityEventFocusChanged) {
   auto engine = GetTestEngine();
-  auto window_binding_handler =
-      std::make_unique<::testing::NiceMock<MockWindowBindingHandler>>();
-  FlutterWindowsViewSpy view(std::move(window_binding_handler));
-  view.SetEngine(engine.get());
+  FlutterWindowsViewSpy view{
+      engine.get(), std::make_unique<NiceMock<MockWindowBindingHandler>>()};
+  EngineModifier modifier{engine.get()};
+  modifier.SetImplicitView(&view);
   view.OnUpdateSemanticsEnabled(true);
 
   auto bridge = GetAccessibilityBridgeSpy(view);

shell/platform/windows/compositor_opengl_unittests.cc

@@ -84,7 +84,7 @@ class CompositorOpenGLTest : public WindowsTest {
     FlutterWindowsEngineBuilder builder{GetContext()};
 
     engine_ = builder.Build();
-    EngineModifier modifier(engine_.get());
+    EngineModifier modifier{engine_.get()};
     modifier.SetEGLManager(std::move(egl_manager));
   }
 
@@ -95,7 +95,8 @@ class CompositorOpenGLTest : public WindowsTest {
     EXPECT_CALL(*window.get(), SetView).Times(1);
     EXPECT_CALL(*window.get(), GetWindowHandle).WillRepeatedly(Return(nullptr));
 
-    view_ = std::make_unique<FlutterWindowsView>(std::move(window));
+    view_ =
+        std::make_unique<FlutterWindowsView>(engine_.get(), std::move(window));
 
     if (add_surface) {
       auto surface = std::make_unique<egl::MockWindowSurface>();
@@ -107,7 +108,8 @@ class CompositorOpenGLTest : public WindowsTest {
       modifier.SetSurface(std::move(surface));
     }
 
-    engine_->SetView(view_.get());
+    EngineModifier modifier{engine_.get()};
+    modifier.SetImplicitView(view_.get());
   }
 
  private:

shell/platform/windows/compositor_software_unittests.cc

@@ -22,8 +22,9 @@ using ::testing::Return;
 
 class MockFlutterWindowsView : public FlutterWindowsView {
  public:
-  MockFlutterWindowsView(std::unique_ptr<WindowBindingHandler> window)
-      : FlutterWindowsView(std::move(window)) {}
+  MockFlutterWindowsView(FlutterWindowsEngine* engine,
+                         std::unique_ptr<WindowBindingHandler> window)
+      : FlutterWindowsView(engine, std::move(window)) {}
   virtual ~MockFlutterWindowsView() = default;
 
   MOCK_METHOD(bool,
@@ -59,9 +60,11 @@ class CompositorSoftwareTest : public WindowsTest {
     EXPECT_CALL(*window.get(), GetWindowHandle).WillRepeatedly(Return(nullptr));
 
     engine_ = builder.Build();
-    view_ = std::make_unique<MockFlutterWindowsView>(std::move(window));
+    view_ = std::make_unique<MockFlutterWindowsView>(engine_.get(),
+                                                     std::move(window));
 
-    engine_->SetView(view_.get());
+    EngineModifier modifier{engine_.get()};
+    modifier.SetImplicitView(view_.get());
   }
 
  private:

shell/platform/windows/cursor_handler_unittests.cc

@@ -11,6 +11,7 @@
 #include "flutter/shell/platform/common/client_wrapper/include/flutter/standard_message_codec.h"
 #include "flutter/shell/platform/common/client_wrapper/include/flutter/standard_method_codec.h"
 #include "flutter/shell/platform/windows/flutter_windows_view.h"
+#include "flutter/shell/platform/windows/testing/engine_modifier.h"
 #include "flutter/shell/platform/windows/testing/flutter_windows_engine_builder.h"
 #include "flutter/shell/platform/windows/testing/mock_window_binding_handler.h"
 #include "flutter/shell/platform/windows/testing/test_binary_messenger.h"
@@ -73,14 +74,16 @@ class CursorHandlerTest : public WindowsTest {
     FlutterWindowsEngineBuilder builder{GetContext()};
 
     auto window = std::make_unique<MockWindowBindingHandler>();
+    EXPECT_CALL(*window.get(), SetView).Times(1);
+    EXPECT_CALL(*window.get(), GetWindowHandle).WillRepeatedly(Return(nullptr));
 
     window_ = window.get();
-    EXPECT_CALL(*window_, SetView).Times(1);
-
     engine_ = builder.Build();
-    view_ = std::make_unique<FlutterWindowsView>(std::move(window));
+    view_ =
+        std::make_unique<FlutterWindowsView>(engine_.get(), std::move(window));
 
-    engine_->SetView(view_.get());
+    EngineModifier modifier{engine_.get()};
+    modifier.SetImplicitView(view_.get());
   }
 
  private:

shell/platform/windows/flutter_window_unittests.cc

@@ -4,6 +4,7 @@
 
 #include "flutter/fml/macros.h"
 #include "flutter/shell/platform/windows/flutter_window.h"
+#include "flutter/shell/platform/windows/testing/flutter_windows_engine_builder.h"
 #include "flutter/shell/platform/windows/testing/mock_window_binding_handler.h"
 #include "flutter/shell/platform/windows/testing/mock_window_binding_handler_delegate.h"
 #include "flutter/shell/platform/windows/testing/windows_test.h"
@@ -26,7 +27,7 @@ static constexpr int32_t kDefaultPointerDeviceId = 0;
 class MockFlutterWindow : public FlutterWindow {
  public:
   MockFlutterWindow(bool reset_view_on_exit = true)
-      : FlutterWindow(), reset_view_on_exit_(reset_view_on_exit) {
+      : reset_view_on_exit_(reset_view_on_exit) {
     ON_CALL(*this, GetDpiScale())
         .WillByDefault(Return(this->FlutterWindow::GetDpiScale()));
   }
@@ -95,8 +96,9 @@ class MockFlutterWindow : public FlutterWindow {
 
 class MockFlutterWindowsView : public FlutterWindowsView {
  public:
-  MockFlutterWindowsView(std::unique_ptr<WindowBindingHandler> window_binding)
-      : FlutterWindowsView(std::move(window_binding)) {}
+  MockFlutterWindowsView(FlutterWindowsEngine* engine,
+                         std::unique_ptr<WindowBindingHandler> window_binding)
+      : FlutterWindowsView(engine, std::move(window_binding)) {}
   ~MockFlutterWindowsView() {}
 
   MOCK_METHOD(void,
@@ -313,12 +315,14 @@ TEST_F(FlutterWindowTest, AccessibilityNodeWithoutView) {
 // Ensure that announcing the alert propagates the message to the alert node.
 // Different screen readers use different properties for alerts.
 TEST_F(FlutterWindowTest, AlertNode) {
-  std::unique_ptr<MockFlutterWindow> win32window =
-      std::make_unique<MockFlutterWindow>();
+  std::unique_ptr<FlutterWindowsEngine> engine =
+      FlutterWindowsEngineBuilder{GetContext()}.Build();
+  auto win32window = std::make_unique<MockFlutterWindow>();
   EXPECT_CALL(*win32window.get(), GetAxFragmentRootDelegate())
       .WillRepeatedly(Return(nullptr));
   EXPECT_CALL(*win32window.get(), OnWindowStateEvent).Times(AnyNumber());
-  MockFlutterWindowsView view(std::move(win32window));
+  EXPECT_CALL(*win32window.get(), GetWindowHandle).Times(AnyNumber());
+  MockFlutterWindowsView view{engine.get(), std::move(win32window)};
   std::wstring message = L"Test alert";
   EXPECT_CALL(view, NotifyWinEventWrapper(_, ax::mojom::Event::kAlert))
       .Times(1);

shell/platform/windows/flutter_windows.cc

@@ -82,12 +82,11 @@ FlutterDesktopViewControllerRef FlutterDesktopViewControllerCreate(
           width, height, engine_ptr->windows_proc_table());
 
   auto engine = std::unique_ptr<flutter::FlutterWindowsEngine>(engine_ptr);
-  auto view = std::make_unique<flutter::FlutterWindowsView>(
-      std::move(window_wrapper), engine_ptr->windows_proc_table());
+  std::unique_ptr<flutter::FlutterWindowsView> view =
+      engine->CreateView(std::move(window_wrapper));
   auto controller = std::make_unique<flutter::FlutterWindowsViewController>(
       std::move(engine), std::move(view));
 
-  controller->view()->SetEngine(controller->engine());
   controller->view()->CreateRenderSurface();
   if (!controller->engine()->running()) {
     if (!controller->engine()->Run()) {

shell/platform/windows/flutter_windows_engine.cc

@@ -483,9 +483,15 @@ bool FlutterWindowsEngine::Stop() {
   return false;
 }
 
-void FlutterWindowsEngine::SetView(FlutterWindowsView* view) {
-  view_ = view;
+std::unique_ptr<FlutterWindowsView> FlutterWindowsEngine::CreateView(
+    std::unique_ptr<WindowBindingHandler> window) {
+  auto view = std::make_unique<FlutterWindowsView>(this, std::move(window),
+                                                   windows_proc_table_);
+
+  view_ = view.get();
   InitializeKeyboard();
+
+  return std::move(view);
 }
 
 void FlutterWindowsEngine::OnVsync(intptr_t baton) {

shell/platform/windows/flutter_windows_engine.h

@@ -111,8 +111,9 @@ class FlutterWindowsEngine {
   // Returns false if stopping the engine fails, or if it was not running.
   virtual bool Stop();
 
-  // Sets the view that is displaying this engine's content.
-  void SetView(FlutterWindowsView* view);
+  // Create the view that is displaying this engine's content.
+  std::unique_ptr<FlutterWindowsView> CreateView(
+      std::unique_ptr<WindowBindingHandler> window);
 
   // The view displaying this engine's content, if any. This will be null for
   // headless engines.