[Windows] Allow plugins to get views

Author: loic-sharma

shell/platform/common/client_wrapper/include/flutter/plugin_registrar.h

@@ -54,7 +54,7 @@ class PluginRegistrar {
   void AddPlugin(std::unique_ptr<Plugin> plugin);
 
  protected:
-  FlutterDesktopPluginRegistrarRef registrar() { return registrar_; }
+  FlutterDesktopPluginRegistrarRef registrar() const { return registrar_; }
 
   // Destroys all owned plugins. Subclasses should call this at the beginning of
   // their destructors to prevent the possibility of an owned plugin trying to

shell/platform/windows/client_wrapper/include/flutter/flutter_view.h

@@ -17,6 +17,7 @@ class FlutterView {
  public:
   explicit FlutterView(FlutterDesktopViewRef view) : view_(view) {}
 
+  // Destroys this reference to the view. The underlying view is not destroyed.
   virtual ~FlutterView() = default;
 
   // Prevent copying.

shell/platform/windows/client_wrapper/include/flutter/plugin_registrar_windows.h

@@ -47,8 +47,21 @@ class PluginRegistrarWindows : public PluginRegistrar {
   PluginRegistrarWindows(PluginRegistrarWindows const&) = delete;
   PluginRegistrarWindows& operator=(PluginRegistrarWindows const&) = delete;
 
+  // Returns the implicit view, or nullptr if there is no implicit view.
+  //
+  // See:
+  // https://api.flutter.dev/flutter/dart-ui/PlatformDispatcher/implicitView.html
   FlutterView* GetView() { return view_.get(); }
 
+  // Returns the view with the given ID, or nullptr if the view does not exist.
+  //
+  // Destroying the shared pointer destroys the reference to the view; it does
+  // not destroy the underlying view.
+  std::shared_ptr<FlutterView> GetViewById(FlutterViewId view_id) const {
+    return std::make_shared<FlutterView>(
+        FlutterDesktopPluginRegistrarGetViewById(registrar(), view_id));
+  }
+
   // Registers |delegate| to receive WindowProc callbacks for the top-level
   // window containing this Flutter instance. Returns an ID that can be used to
   // unregister the handler.

shell/platform/windows/client_wrapper/plugin_registrar_windows_unittests.cc

@@ -73,6 +73,15 @@ TEST(PluginRegistrarWindowsTest, GetView) {
   EXPECT_NE(registrar.GetView(), nullptr);
 }
 
+TEST(PluginRegistrarWindowsTest, GetViewById) {
+  testing::ScopedStubFlutterWindowsApi scoped_api_stub(
+      std::make_unique<TestWindowsApi>());
+  auto test_api = static_cast<TestWindowsApi*>(scoped_api_stub.stub());
+  PluginRegistrarWindows registrar(
+      reinterpret_cast<FlutterDesktopPluginRegistrarRef>(1));
+  EXPECT_NE(registrar.GetViewById(123), nullptr);
+}
+
 // Tests that the registrar runs plugin destructors before its own teardown.
 TEST(PluginRegistrarWindowsTest, PluginDestroyedBeforeRegistrar) {
   auto dummy_registrar_handle =

shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.cc

@@ -198,6 +198,13 @@ FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetView(
   return reinterpret_cast<FlutterDesktopViewRef>(1);
 }
 
+FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetViewById(
+    FlutterDesktopPluginRegistrarRef controller,
+    FlutterDesktopViewId view_id) {
+  // The stub ignores this, so just return an arbitrary non-zero value.
+  return reinterpret_cast<FlutterDesktopViewRef>(1);
+}
+
 void FlutterDesktopPluginRegistrarRegisterTopLevelWindowProcDelegate(
     FlutterDesktopPluginRegistrarRef registrar,
     FlutterDesktopWindowProcCallback delegate,

shell/platform/windows/flutter_windows.cc

@@ -261,12 +261,15 @@ void FlutterDesktopEngineRegisterPlatformViewType(
 
 FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetView(
     FlutterDesktopPluginRegistrarRef registrar) {
-  // TODO(loicsharma): Add |FlutterDesktopPluginRegistrarGetViewById| and
-  // deprecate this API as it makes single view assumptions.
-  // https://github.com/flutter/flutter/issues/143767
   return HandleForView(registrar->engine->view(flutter::kImplicitViewId));
 }
 
+FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetViewById(
+    FlutterDesktopPluginRegistrarRef registrar,
+    FlutterDesktopViewId view_id) {
+  return HandleForView(registrar->engine->view(view_id));
+}
+
 void FlutterDesktopPluginRegistrarRegisterTopLevelWindowProcDelegate(
     FlutterDesktopPluginRegistrarRef registrar,
     FlutterDesktopWindowProcCallback delegate,

shell/platform/windows/flutter_windows_unittests.cc

@@ -333,6 +333,64 @@ TEST_F(WindowsTest, GetGraphicsAdapter) {
   ASSERT_TRUE(SUCCEEDED(dxgi_adapter->GetDesc(&desc)));
 }
 
+// Implicit view has the implicit view ID.
+TEST_F(WindowsTest, PluginRegistrarGetImplicitView) {
+  auto& context = GetContext();
+  WindowsConfigBuilder builder(context);
+  ViewControllerPtr controller{builder.Run()};
+  ASSERT_NE(controller, nullptr);
+
+  FlutterDesktopEngineRef engine =
+      FlutterDesktopViewControllerGetEngine(controller.get());
+  FlutterDesktopPluginRegistrarRef registrar =
+      FlutterDesktopEngineGetPluginRegistrar(engine, "foo_bar");
+  FlutterDesktopViewRef implicit_view =
+      FlutterDesktopPluginRegistrarGetView(registrar);
+
+  ASSERT_NE(implicit_view, nullptr);
+}
+
+TEST_F(WindowsTest, PluginRegistrarGetView) {
+  auto& context = GetContext();
+  WindowsConfigBuilder builder(context);
+  ViewControllerPtr controller{builder.Run()};
+  ASSERT_NE(controller, nullptr);
+
+  FlutterDesktopEngineRef engine =
+      FlutterDesktopViewControllerGetEngine(controller.get());
+  FlutterDesktopPluginRegistrarRef registrar =
+      FlutterDesktopEngineGetPluginRegistrar(engine, "foo_bar");
+
+  FlutterDesktopViewId view_id =
+      FlutterDesktopViewControllerGetViewId(controller.get());
+  FlutterDesktopViewRef view =
+      FlutterDesktopPluginRegistrarGetViewById(registrar, view_id);
+
+  FlutterDesktopViewRef view_123 = FlutterDesktopPluginRegistrarGetViewById(
+      registrar, static_cast<FlutterDesktopViewId>(123));
+
+  ASSERT_NE(view, nullptr);
+  ASSERT_EQ(view_123, nullptr);
+}
+
+TEST_F(WindowsTest, PluginRegistrarGetViewHeadless) {
+  auto& context = GetContext();
+  WindowsConfigBuilder builder(context);
+  EnginePtr engine{builder.RunHeadless()};
+  ASSERT_NE(engine, nullptr);
+
+  FlutterDesktopPluginRegistrarRef registrar =
+      FlutterDesktopEngineGetPluginRegistrar(engine.get(), "foo_bar");
+
+  FlutterDesktopViewRef implicit_view =
+      FlutterDesktopPluginRegistrarGetView(registrar);
+  FlutterDesktopViewRef view_123 = FlutterDesktopPluginRegistrarGetViewById(
+      registrar, static_cast<FlutterDesktopViewId>(123));
+
+  ASSERT_EQ(implicit_view, nullptr);
+  ASSERT_EQ(view_123, nullptr);
+}
+
 // Verify the app does not crash if EGL initializes successfully but
 // the rendering surface cannot be created.
 TEST_F(WindowsTest, SurfaceOptional) {

shell/platform/windows/public/flutter_windows.h

@@ -249,10 +249,22 @@ typedef bool (*FlutterDesktopWindowProcCallback)(HWND /* hwnd */,
                                                  void* /* user data */,
                                                  LRESULT* result);
 
-// Returns the view associated with this registrar's engine instance.
+// Returns the implicit view associated with this registrar's engine instance,
+// or null if there is no implicit view.
+//
+// See:
+// https://api.flutter.dev/flutter/dart-ui/PlatformDispatcher/implicitView.html
+//
+// DEPRECATED: Use |FlutterDesktopPluginRegistrarGetViewById| instead.
 FLUTTER_EXPORT FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetView(
     FlutterDesktopPluginRegistrarRef registrar);
 
+// Returns the view associated with the registrar's engine instance, or null if
+// the view does not exist.
+FLUTTER_EXPORT FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetViewById(
+    FlutterDesktopPluginRegistrarRef registrar,
+    FlutterDesktopViewId view_id);
+
 FLUTTER_EXPORT void
 FlutterDesktopPluginRegistrarRegisterTopLevelWindowProcDelegate(
     FlutterDesktopPluginRegistrarRef registrar,