[macOS] Group per-view information in FlutterCompositor into a class

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

@@ -7,6 +7,7 @@
 
 #include <functional>
 #include <list>
+#include <unordered_map>
 
 #include "flutter/fml/macros.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformViewController.h"
@@ -34,9 +35,9 @@ class FlutterCompositor {
   // 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,
-                             FlutterTimeConverter* time_converter,
-                             FlutterPlatformViewController* platform_views_controller);
+  FlutterCompositor(id<FlutterViewProvider> view_provider,
+                    FlutterTimeConverter* time_converter,
+                    FlutterPlatformViewController* platform_views_controller);
 
   ~FlutterCompositor() = default;
 
@@ -56,19 +57,34 @@ class FlutterCompositor {
                           FlutterBackingStore* backing_store_out);
 
   // Presents the FlutterLayers by updating the FlutterView specified by
-  // `view_id` using the layer content. Sets frame_started_ to false.
+  // `view_id` using the layer content.
   bool Present(FlutterViewId view_id, const FlutterLayer** layers, size_t layers_count);
 
  private:
-  void PresentPlatformViews(FlutterView* default_base_view,
-                            const std::vector<PlatformViewLayerWithIndex>& platform_views_layers);
-
-  // Presents the platform view layer represented by `layer`. `layer_index` is
-  // 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`.
-  FlutterMutatorView* PresentPlatformView(FlutterView* default_base_view,
-                                          const PlatformViewLayer& layer,
-                                          size_t index);
+  // A class that contains the information for a view to be presented.
+  class ViewPresenter {
+   public:
+    ViewPresenter();
+
+    void PresentPlatformViews(FlutterView* default_base_view,
+                              const std::vector<PlatformViewLayerWithIndex>& platform_views,
+                              const FlutterPlatformViewController* platform_views_controller);
+
+   private:
+    // Platform view to FlutterMutatorView that contains it.
+    NSMapTable<NSView*, FlutterMutatorView*>* mutator_views_;
+
+    // Presents the platform view layer represented by `layer`. `layer_index` is
+    // 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`.
+    FlutterMutatorView* PresentPlatformView(
+        FlutterView* default_base_view,
+        const PlatformViewLayer& layer,
+        size_t layer_position,
+        const FlutterPlatformViewController* platform_views_controller);
+
+    FML_DISALLOW_COPY_AND_ASSIGN(ViewPresenter);
+  };
 
   // Where the compositor can query FlutterViews. Must not be null.
   id<FlutterViewProvider> const view_provider_;
@@ -79,8 +95,7 @@ class FlutterCompositor {
   // The controller used to manage creation and deletion of platform views.
   const FlutterPlatformViewController* platform_view_controller_;
 
-  // Platform view to FlutterMutatorView that contains it.
-  NSMapTable<NSView*, FlutterMutatorView*>* mutator_views_;
+  std::unordered_map<int64_t, ViewPresenter> presenters_;
 
   FML_DISALLOW_COPY_AND_ASSIGN(FlutterCompositor);
 };

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

@@ -27,8 +27,7 @@
                                      FlutterPlatformViewController* platform_view_controller)
     : view_provider_(view_provider),
       time_converter_(time_converter),
-      platform_view_controller_(platform_view_controller),
-      mutator_views_([NSMapTable strongToStrongObjectsMapTable]) {
+      platform_view_controller_(platform_view_controller) {
   FML_CHECK(view_provider != nullptr) << "view_provider cannot be nullptr";
 }
 
@@ -55,6 +54,10 @@
 bool FlutterCompositor::Present(FlutterViewId view_id,
                                 const FlutterLayer** layers,
                                 size_t layers_count) {
+  // TODO(dkwingsmt): The macOS embedder only supports rendering to the implicit
+  // view for now. As it supports adding more views, this assertion should be
+  // lifted. https://github.com/flutter/flutter/issues/142845
+  FML_DCHECK(view_id == kFlutterImplicitViewId);
   FlutterView* view = [view_provider_ viewForId:view_id];
   if (!view) {
     return false;
@@ -98,24 +101,32 @@
   [view.surfaceManager presentSurfaces:surfaces
                                 atTime:presentation_time
                                 notify:^{
-                                  PresentPlatformViews(view, *platform_views_layers);
+                                  // Gets a presenter or create a new one for the view.
+                                  ViewPresenter& presenter = presenters_[view_id];
+                                  presenter.PresentPlatformViews(view, *platform_views_layers,
+                                                                 platform_view_controller_);
                                 }];
 
   return true;
 }
 
-void FlutterCompositor::PresentPlatformViews(
+FlutterCompositor::ViewPresenter::ViewPresenter()
+    : mutator_views_([NSMapTable strongToStrongObjectsMapTable]) {}
+
+void FlutterCompositor::ViewPresenter::PresentPlatformViews(
     FlutterView* default_base_view,
-    const std::vector<PlatformViewLayerWithIndex>& platform_views) {
+    const std::vector<PlatformViewLayerWithIndex>& platform_views,
+    const FlutterPlatformViewController* platform_view_controller) {
   FML_DCHECK([[NSThread currentThread] isMainThread])
       << "Must be on the main thread to present platform views";
 
   // Active mutator views for this frame.
   NSMutableArray<FlutterMutatorView*>* present_mutators = [NSMutableArray array];
 
   for (const auto& platform_view : platform_views) {
-    [present_mutators addObject:PresentPlatformView(default_base_view, platform_view.first,
-                                                    platform_view.second)];
+    FlutterMutatorView* container = PresentPlatformView(
+        default_base_view, platform_view.first, platform_view.second, platform_view_controller);
+    [present_mutators addObject:container];
   }
 
   NSMutableArray<FlutterMutatorView*>* obsolete_mutators =
@@ -127,17 +138,19 @@
     [mutator removeFromSuperview];
   }
 
-  [platform_view_controller_ disposePlatformViews];
+  [platform_view_controller disposePlatformViews];
 }
 
-FlutterMutatorView* FlutterCompositor::PresentPlatformView(FlutterView* default_base_view,
-                                                           const PlatformViewLayer& layer,
-                                                           size_t index) {
+FlutterMutatorView* FlutterCompositor::ViewPresenter::PresentPlatformView(
+    FlutterView* default_base_view,
+    const PlatformViewLayer& layer,
+    size_t index,
+    const FlutterPlatformViewController* platform_view_controller) {
   FML_DCHECK([[NSThread currentThread] isMainThread])
       << "Must be on the main thread to present platform views";
 
   int64_t platform_view_id = layer.identifier();
-  NSView* platform_view = [platform_view_controller_ platformViewWithID:platform_view_id];
+  NSView* platform_view = [platform_view_controller platformViewWithID:platform_view_id];
 
   FML_DCHECK(platform_view) << "Platform view not found for id: " << platform_view_id;