[macOS, multiwindow] Compositor gets FlutterView lazily (flutter#36392)

ci/licenses_golden/licenses_flutter

@@ -2662,6 +2662,10 @@ FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterViewC
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterViewControllerTestUtils.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterViewControllerTestUtils.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterViewEngineProvider.h
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterViewEngineProvider.mm
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterViewEngineProviderUnittests.mm
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterViewProvider.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/KeyCodeMap.g.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/KeyCodeMap_Internal.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/MacOSGLContextSwitch.h

shell/platform/darwin/macos/BUILD.gn

@@ -121,6 +121,9 @@ source_set("flutter_framework_source") {
     "framework/Source/FlutterView.mm",
     "framework/Source/FlutterViewController.mm",
     "framework/Source/FlutterViewController_Internal.h",
+    "framework/Source/FlutterViewEngineProvider.h",
+    "framework/Source/FlutterViewEngineProvider.mm",
+    "framework/Source/FlutterViewProvider.h",
     "framework/Source/KeyCodeMap.g.mm",
     "framework/Source/MacOSGLContextSwitch.h",
     "framework/Source/MacOSGLContextSwitch.mm",
@@ -202,6 +205,7 @@ executable("flutter_desktop_darwin_unittests") {
     "framework/Source/FlutterViewControllerTest.mm",
     "framework/Source/FlutterViewControllerTestUtils.h",
     "framework/Source/FlutterViewControllerTestUtils.mm",
+    "framework/Source/FlutterViewEngineProviderUnitTests.mm",
     "framework/Source/TestFlutterPlatformView.h",
     "framework/Source/TestFlutterPlatformView.mm",
   ]

shell/platform/darwin/macos/framework/Source/FlutterCompositor.h

@@ -9,7 +9,8 @@
 #include <list>
 
 #include "flutter/fml/macros.h"
-#include "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
+#include "flutter/shell/platform/darwin/macos/framework/Source/FlutterView.h"
+#include "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewProvider.h"
 #include "flutter/shell/platform/embedder/embedder.h"
 
 namespace flutter {
@@ -19,7 +20,12 @@ namespace flutter {
 // Platform views are not yet supported.
 class FlutterCompositor {
  public:
-  explicit FlutterCompositor(FlutterViewController* view_controller);
+  // Create a FlutterCompositor with a view provider.
+  //
+  // The view_provider is used to query FlutterViews from view IDs,
+  // which are used for presenting and creating backing stores.
+  // It must not be null, and is typically FlutterViewEngineProvider.
+  explicit FlutterCompositor(id<FlutterViewProvider> view_provider);
 
   virtual ~FlutterCompositor() = default;
 
@@ -62,7 +68,10 @@ class FlutterCompositor {
   typedef enum { kStarted, kPresenting, kEnded } FrameStatus;
 
  protected:
-  __weak const FlutterViewController* view_controller_;
+  // Get the view associated with the view ID.
+  //
+  // Returns nil if the ID is invalid.
+  FlutterView* GetView(uint64_t view_id);
 
   // Gets and sets the FrameStatus for the current frame.
   void SetFrameStatus(FrameStatus frame_status);
@@ -76,15 +85,19 @@ class FlutterCompositor {
   bool EndFrame(bool has_flutter_content);
 
   // Creates a CALayer object which is backed by the supplied IOSurface, and
-  // adds it to the root CALayer for this FlutterViewController's view.
+  // adds it to the root CALayer for the given view.
   void InsertCALayerForIOSurface(
+      FlutterView* view,
       const IOSurfaceRef& io_surface,
       CATransform3D transform = CATransform3DIdentity);
 
  private:
   // A list of the active CALayer objects for the frame that need to be removed.
   std::list<CALayer*> active_ca_layers_;
 
+  // Where the compositor can query FlutterViews. Must not be null.
+  id<FlutterViewProvider> const view_provider_;
+
   // Callback set by the embedder to be called when the layer tree has been
   // correctly set up for this frame.
   PresentCallback present_callback_;

shell/platform/darwin/macos/framework/Source/FlutterCompositor.mm

@@ -7,10 +7,9 @@
 
 namespace flutter {
 
-FlutterCompositor::FlutterCompositor(FlutterViewController* view_controller) {
-  FML_CHECK(view_controller != nullptr) << "FlutterViewController* cannot be nullptr";
-
-  view_controller_ = view_controller;
+FlutterCompositor::FlutterCompositor(id<FlutterViewProvider> view_provider)
+    : view_provider_(view_provider) {
+  FML_CHECK(view_provider != nullptr) << "FlutterViewProvider* cannot be nullptr";
 }
 
 void FlutterCompositor::SetPresentCallback(
@@ -35,6 +34,10 @@
   return status;
 }
 
+FlutterView* FlutterCompositor::GetView(uint64_t view_id) {
+  return [view_provider_ getView:view_id];
+}
+
 void FlutterCompositor::SetFrameStatus(FlutterCompositor::FrameStatus frame_status) {
   frame_status_ = frame_status;
 }
@@ -43,14 +46,15 @@
   return frame_status_;
 }
 
-void FlutterCompositor::InsertCALayerForIOSurface(const IOSurfaceRef& io_surface,
+void FlutterCompositor::InsertCALayerForIOSurface(FlutterView* view,
+                                                  const IOSurfaceRef& io_surface,
                                                   CATransform3D transform) {
   // FlutterCompositor manages the lifecycle of CALayers.
   CALayer* content_layer = [[CALayer alloc] init];
   content_layer.transform = transform;
-  content_layer.frame = view_controller_.flutterView.layer.bounds;
+  content_layer.frame = view.layer.bounds;
   [content_layer setContents:(__bridge id)io_surface];
-  [view_controller_.flutterView.layer addSublayer:content_layer];
+  [view.layer addSublayer:content_layer];
 
   active_ca_layers_.push_back(content_layer);
 }

shell/platform/darwin/macos/framework/Source/FlutterEngine.mm

@@ -21,6 +21,7 @@
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformViewController.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterRenderingBackend.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewEngineProvider.h"
 #include "flutter/shell/platform/embedder/embedder.h"
 
 /**
@@ -211,6 +212,8 @@ @implementation FlutterEngine {
   // This is either a FlutterGLCompositor or a FlutterMetalCompositor instance.
   std::unique_ptr<flutter::FlutterCompositor> _macOSCompositor;
 
+  FlutterViewEngineProvider* _viewProvider;
+
   // FlutterCompositor is copied and used in embedder.cc.
   FlutterCompositor _compositor;
 
@@ -244,6 +247,7 @@ - (instancetype)initWithName:(NSString*)labelPrefix
   _currentMessengerConnection = 1;
   _allowHeadlessExecution = allowHeadlessExecution;
   _semanticsEnabled = NO;
+  _viewProvider = [[FlutterViewEngineProvider alloc] initWithEngine:self];
 
   _embedderAPI.struct_size = sizeof(FlutterEngineProcTable);
   FlutterEngineGetProcAddresses(&_embedderAPI);
@@ -437,12 +441,12 @@ - (FlutterCompositor*)createFlutterCompositor {
   if ([FlutterRenderingBackend renderUsingMetal]) {
     FlutterMetalRenderer* metalRenderer = reinterpret_cast<FlutterMetalRenderer*>(_renderer);
     _macOSCompositor = std::make_unique<flutter::FlutterMetalCompositor>(
-        _viewController, _platformViewController, metalRenderer.device);
+        _viewProvider, _platformViewController, metalRenderer.device);
   } else {
     FlutterOpenGLRenderer* openGLRenderer = reinterpret_cast<FlutterOpenGLRenderer*>(_renderer);
     [openGLRenderer.openGLContext makeCurrentContext];
-    _macOSCompositor = std::make_unique<flutter::FlutterGLCompositor>(_viewController,
-                                                                      openGLRenderer.openGLContext);
+    _macOSCompositor =
+        std::make_unique<flutter::FlutterGLCompositor>(_viewProvider, openGLRenderer.openGLContext);
   }
   _macOSCompositor->SetPresentCallback([weakSelf](bool has_flutter_content) {
     if (has_flutter_content) {

shell/platform/darwin/macos/framework/Source/FlutterGLCompositor.h

@@ -19,7 +19,7 @@ namespace flutter {
 // FlutterGLCompositor is created and destroyed by FlutterEngine.
 class FlutterGLCompositor : public FlutterCompositor {
  public:
-  FlutterGLCompositor(FlutterViewController* view_controller,
+  FlutterGLCompositor(id<FlutterViewProvider> view_provider,
                       NSOpenGLContext* opengl_context);
 
   virtual ~FlutterGLCompositor() = default;

shell/platform/darwin/macos/framework/Source/FlutterGLCompositor.mm

@@ -19,13 +19,17 @@
 
 namespace flutter {
 
-FlutterGLCompositor::FlutterGLCompositor(FlutterViewController* view_controller,
+FlutterGLCompositor::FlutterGLCompositor(id<FlutterViewProvider> view_provider,
                                          NSOpenGLContext* opengl_context)
-    : FlutterCompositor(view_controller), open_gl_context_(opengl_context) {}
+    : FlutterCompositor(view_provider), open_gl_context_(opengl_context) {}
 
 bool FlutterGLCompositor::CreateBackingStore(const FlutterBackingStoreConfig* config,
                                              FlutterBackingStore* backing_store_out) {
-  if (!view_controller_) {
+  // TODO(dkwingsmt): This class only supports single-view for now. As more
+  // classes are gradually converted to multi-view, it should get the view ID
+  // from somewhere.
+  FlutterView* view = GetView(kFlutterDefaultViewId);
+  if (!view) {
     return false;
   }
 
@@ -36,8 +40,7 @@
     // If the backing store is for the first layer, return the fbo for the
     // FlutterView.
     FlutterOpenGLRenderBackingStore* backingStore =
-        reinterpret_cast<FlutterOpenGLRenderBackingStore*>(
-            [view_controller_.flutterView backingStoreForSize:size]);
+        reinterpret_cast<FlutterOpenGLRenderBackingStore*>([view backingStoreForSize:size]);
     backing_store_out->open_gl.framebuffer.name = backingStore.frameBufferID;
   } else {
     FlutterFrameBufferProvider* fb_provider =
@@ -75,6 +78,14 @@
 }
 
 bool FlutterGLCompositor::Present(const FlutterLayer** layers, size_t layers_count) {
+  // TODO(dkwingsmt): This class only supports single-view for now. As more
+  // classes are gradually converted to multi-view, it should get the view ID
+  // from somewhere.
+  FlutterView* view = GetView(kFlutterDefaultViewId);
+  if (!view) {
+    return false;
+  }
+
   SetFrameStatus(FrameStatus::kPresenting);
 
   bool has_flutter_content = false;
@@ -93,7 +104,7 @@
 
           // The surface is an OpenGL texture, which means it has origin in bottom left corner
           // and needs to be flipped vertically
-          InsertCALayerForIOSurface(io_surface, CATransform3DMakeScale(1, -1, 1));
+          InsertCALayerForIOSurface(view, io_surface, CATransform3DMakeScale(1, -1, 1));
         }
         has_flutter_content = true;
         break;

shell/platform/darwin/macos/framework/Source/FlutterGLCompositorUnittests.mm

@@ -3,18 +3,52 @@
 // found in the LICENSE file.
 
 #import <Foundation/Foundation.h>
+#import <OCMock/OCMock.h>
 
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterGLCompositor.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewControllerTestUtils.h"
 #import "flutter/testing/testing.h"
 
+@interface FlutterViewMockProviderGL : NSObject <FlutterViewProvider> {
+  FlutterView* _defaultView;
+}
+/**
+ * Create a FlutterViewMockProviderGL with the provided view as the default view.
+ */
+- (nonnull instancetype)initWithDefaultView:(nonnull FlutterView*)view;
+@end
+
+@implementation FlutterViewMockProviderGL
+
+- (nonnull instancetype)initWithDefaultView:(nonnull FlutterView*)view {
+  self = [super init];
+  if (self != nil) {
+    _defaultView = view;
+  }
+  return self;
+}
+
+- (nullable FlutterView*)getView:(uint64_t)viewId {
+  if (viewId == kFlutterDefaultViewId) {
+    return _defaultView;
+  }
+  return nil;
+}
+
+@end
+
 namespace flutter::testing {
+namespace {
 
-TEST(FlutterGLCompositorTest, TestPresent) {
-  id mockViewController = CreateMockViewController();
+id<FlutterViewProvider> MockViewProvider() {
+  id viewMock = OCMClassMock([FlutterView class]);
+  return [[FlutterViewMockProviderGL alloc] initWithDefaultView:viewMock];
+}
+}  // namespace
 
+TEST(FlutterGLCompositorTest, TestPresent) {
   std::unique_ptr<flutter::FlutterGLCompositor> macos_compositor =
-      std::make_unique<FlutterGLCompositor>(mockViewController, nullptr);
+      std::make_unique<FlutterGLCompositor>(MockViewProvider(), nullptr);
 
   bool flag = false;
   macos_compositor->SetPresentCallback([f = &flag](bool has_flutter_content) {

shell/platform/darwin/macos/framework/Source/FlutterMetalCompositor.h

@@ -14,7 +14,7 @@ namespace flutter {
 class FlutterMetalCompositor : public FlutterCompositor {
  public:
   explicit FlutterMetalCompositor(
-      FlutterViewController* view_controller,
+      id<FlutterViewProvider> view_provider,
       FlutterPlatformViewController* platform_views_controller,
       id<MTLDevice> mtl_device);
 
@@ -46,8 +46,11 @@ class FlutterMetalCompositor : public FlutterCompositor {
 
  private:
   // Presents the platform view layer represented by `layer`. `layer_index` is
-  // used to position the layer in the z-axis.
-  void PresentPlatformView(const FlutterLayer* layer, size_t layer_index);
+  // used to position the layer in the z-axis. If the layer does not have a
+  // superview, it will become subview of `default_base_view`.
+  void PresentPlatformView(FlutterView* default_base_view,
+                           const FlutterLayer* layer,
+                           size_t layer_position);
 
   const id<MTLDevice> mtl_device_;
   const FlutterPlatformViewController* platform_views_controller_;