From 57971ec9c273cb3e2512b0fb7d80211fcabbb44c Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Tue, 4 Oct 2022 10:10:47 -0700
Subject: [PATCH 01/15] Impl

---
 .../macos/framework/Source/FlutterEngine.mm   |  6 +--
 .../framework/Source/FlutterMetalRenderer.h   |  4 +-
 .../framework/Source/FlutterMetalRenderer.mm  | 36 +++++++---------
 .../Source/FlutterMetalRendererTest.mm        |  6 +--
 .../framework/Source/FlutterOpenGLRenderer.h  |  2 +-
 .../framework/Source/FlutterOpenGLRenderer.mm | 43 ++++++++++---------
 .../Source/FlutterOpenGLRendererTest.mm       |  6 +--
 .../macos/framework/Source/FlutterRenderer.h  | 11 ++---
 8 files changed, 52 insertions(+), 62 deletions(-)

diff --git a/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm b/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
index 9c15b52f7d8ff..519b5b867ffdc 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
@@ -411,7 +411,6 @@ - (void)loadAOTData:(NSString*)assetsDir {
 - (void)setViewController:(FlutterViewController*)controller {
   if (_viewController != controller) {
     _viewController = controller;
-    [_renderer setFlutterView:controller.flutterView];
 
     if (_semanticsEnabled && _bridge) {
       _bridge->UpdateDelegate(
@@ -445,10 +444,11 @@ - (FlutterCompositor*)createFlutterCompositor {
                                                                       openGLRenderer.openGLContext);
   }
   _macOSCompositor->SetPresentCallback([weakSelf](bool has_flutter_content) {
+    FlutterView* view = weakSelf.viewController.flutterView;
     if (has_flutter_content) {
-      return [weakSelf.renderer present] == YES;
+      return [weakSelf.renderer present:view] == YES;
     } else {
-      [weakSelf.renderer presentWithoutContent];
+      [weakSelf.renderer presentWithoutContent:view];
       return true;
     }
   });
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
index 7d44311ed491b..44a3d132ca363 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
@@ -25,9 +25,9 @@
 @property(nonatomic, readonly, nonnull) id<MTLCommandQueue> commandQueue;
 
 /**
- * Creates a Metal texture for the given size.
+ * Creates a Metal texture for the given view with the given size.
  */
-- (FlutterMetalTexture)createTextureForSize:(CGSize)size;
+- (FlutterMetalTexture)createTextureForView:(nonnull FlutterView*)view size:(CGSize)size;
 
 /**
  * Populates the texture registry with the provided metalTexture.
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
index b7e0d0d65f281..8ab7a33fea3c6 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
@@ -14,13 +14,21 @@
 
 static FlutterMetalTexture OnGetNextDrawable(FlutterEngine* engine,
                                              const FlutterFrameInfo* frameInfo) {
+  FlutterViewController* viewController = engine.viewController;
+  if (viewController == nil) {
+    return FlutterMetalTexture{}; // TODO
+  }
   CGSize size = CGSizeMake(frameInfo->size.width, frameInfo->size.height);
   FlutterMetalRenderer* metalRenderer = reinterpret_cast<FlutterMetalRenderer*>(engine.renderer);
-  return [metalRenderer createTextureForSize:size];
+  return [metalRenderer createTextureForView:viewController.flutterView size:size];
 }
 
 static bool OnPresentDrawable(FlutterEngine* engine, const FlutterMetalTexture* texture) {
-  return [engine.renderer present];
+  FlutterViewController* viewController = engine.viewController;
+  if (viewController == nil) {
+    return false;
+  }
+  return [engine.renderer present:viewController.flutterView];
 }
 
 static bool OnAcquireExternalTexture(FlutterEngine* engine,
@@ -35,8 +43,6 @@ static bool OnAcquireExternalTexture(FlutterEngine* engine,
 #pragma mark - FlutterMetalRenderer implementation
 
 @implementation FlutterMetalRenderer {
-  FlutterView* _flutterView;
-
   FlutterDarwinContextMetal* _darwinMetalContext;
 }
 
@@ -61,10 +67,6 @@ - (instancetype)initWithFlutterEngine:(nonnull FlutterEngine*)flutterEngine {
   return self;
 }
 
-- (void)setFlutterView:(FlutterView*)view {
-  _flutterView = view;
-}
-
 - (FlutterRendererConfig)createRendererConfig {
   FlutterRendererConfig config = {
       .type = FlutterRendererType::kMetal,
@@ -83,9 +85,9 @@ - (FlutterRendererConfig)createRendererConfig {
 
 #pragma mark - Embedder callback implementations.
 
-- (FlutterMetalTexture)createTextureForSize:(CGSize)size {
+- (FlutterMetalTexture)createTextureForView:(FlutterView*)view size:(CGSize)size {
   FlutterMetalRenderBackingStore* backingStore =
-      (FlutterMetalRenderBackingStore*)[_flutterView backingStoreForSize:size];
+      (FlutterMetalRenderBackingStore*)[view backingStoreForSize:size];
   id<MTLTexture> texture = backingStore.texture;
   FlutterMetalTexture embedderTexture;
   embedderTexture.struct_size = sizeof(FlutterMetalTexture);
@@ -94,19 +96,13 @@ - (FlutterMetalTexture)createTextureForSize:(CGSize)size {
   return embedderTexture;
 }
 
-- (BOOL)present {
-  if (!_flutterView) {
-    return NO;
-  }
-  [_flutterView present];
+- (BOOL)present:(FlutterView*)view {
+  [view present];
   return YES;
 }
 
-- (void)presentWithoutContent {
-  if (!_flutterView) {
-    return;
-  }
-  [_flutterView presentWithoutContent];
+- (void)presentWithoutContent:(FlutterView*)view {
+  [view presentWithoutContent];
 }
 
 #pragma mark - FlutterTextureRegistrar methods.
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm
index e045bf09c0d71..b1b84295a4992 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm
@@ -31,8 +31,7 @@
   FlutterMetalRenderer* renderer = [[FlutterMetalRenderer alloc] initWithFlutterEngine:engine];
   id mockFlutterView = OCMClassMock([FlutterView class]);
   [(FlutterView*)[mockFlutterView expect] present];
-  [renderer setFlutterView:mockFlutterView];
-  [renderer present];
+  [renderer present:mockFlutterView];
 }
 
 TEST(FlutterMetalRenderer, TextureReturnedByFlutterView) {
@@ -47,8 +46,7 @@
   frameInfo.size = dimensions;
   CGSize size = CGSizeMake(dimensions.width, dimensions.height);
   [[mockFlutterView expect] backingStoreForSize:size];
-  [renderer setFlutterView:mockFlutterView];
-  [renderer createTextureForSize:size];
+  [renderer createTextureForView:mockFlutterView size:size];
 }
 
 }  // namespace flutter::testing
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
index 2d8bf08d90c08..95999adc41f25 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
@@ -37,7 +37,7 @@
 /**
  * Called by the engine when framebuffer object ID is requested.
  */
-- (uint32_t)fboForFrameInfo:(nonnull const FlutterFrameInfo*)info;
+- (uint32_t)fboForView:(nonnull FlutterView*)view frameInfo:(nonnull const FlutterFrameInfo*)info;
 
 /**
  * Makes the resource context the current context.
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
index 9c694480d8421..1c695e813eb90 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
@@ -20,12 +20,20 @@ static bool OnClearCurrent(FlutterEngine* engine) {
 }
 
 static bool OnPresent(FlutterEngine* engine) {
-  return [engine.renderer present];
+  FlutterViewController* viewController = engine.viewController;
+  if (viewController == nil) {
+    return false;
+  }
+  return [engine.renderer present:viewController.flutterView];
 }
 
 static uint32_t OnFBO(FlutterEngine* engine, const FlutterFrameInfo* info) {
+  FlutterViewController* viewController = engine.viewController;
+  if (viewController == nil) {
+    return -1; // TODO
+  }
   FlutterOpenGLRenderer* openGLRenderer = reinterpret_cast<FlutterOpenGLRenderer*>(engine.renderer);
-  return [openGLRenderer fboForFrameInfo:info];
+  return [openGLRenderer fboForView:viewController.flutterView frameInfo:info];
 }
 
 static bool OnMakeResourceCurrent(FlutterEngine* engine) {
@@ -46,8 +54,6 @@ static bool OnAcquireExternalTexture(FlutterEngine* engine,
 #pragma mark - FlutterOpenGLRenderer implementation.
 
 @implementation FlutterOpenGLRenderer {
-  FlutterView* _flutterView;
-
   // The context provided to the Flutter engine for rendering to the FlutterView. This is lazily
   // created during initialization of the FlutterView. This is used to render content into the
   // FlutterView.
@@ -62,12 +68,12 @@ - (instancetype)initWithFlutterEngine:(FlutterEngine*)flutterEngine {
   return self;
 }
 
-- (void)setFlutterView:(FlutterView*)view {
-  _flutterView = view;
-  if (!view) {
-    _resourceContext = nil;
-  }
-}
+// - (void)setFlutterView:(FlutterView*)view {
+//   _flutterView = view;
+//   if (!view) {
+//     _resourceContext = nil;
+//   }
+// }
 
 - (BOOL)makeCurrent {
   if (!_openGLContext) {
@@ -82,25 +88,22 @@ - (BOOL)clearCurrent {
   return true;
 }
 
-- (BOOL)present {
-  if (!_openGLContext || !_flutterView) {
+- (BOOL)present:(FlutterView*)view {
+  if (!_openGLContext) {
     return NO;
   }
-  [_flutterView present];
+  [view present];
   return YES;
 }
 
-- (void)presentWithoutContent {
-  if (!_flutterView) {
-    return;
-  }
-  [_flutterView presentWithoutContent];
+- (void)presentWithoutContent:(FlutterView*)view {
+  [view presentWithoutContent];
 }
 
-- (uint32_t)fboForFrameInfo:(const FlutterFrameInfo*)info {
+- (uint32_t)fboForView:(FlutterView*)view frameInfo:(const FlutterFrameInfo*)info {
   CGSize size = CGSizeMake(info->size.width, info->size.height);
   FlutterOpenGLRenderBackingStore* backingStore =
-      reinterpret_cast<FlutterOpenGLRenderBackingStore*>([_flutterView backingStoreForSize:size]);
+      reinterpret_cast<FlutterOpenGLRenderBackingStore*>([view backingStoreForSize:size]);
   return backingStore.frameBufferID;
 }
 
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRendererTest.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRendererTest.mm
index 808e32686dd6c..ee33b524d1cdb 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRendererTest.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRendererTest.mm
@@ -114,9 +114,8 @@ - (nullable instancetype)initWithGLRenderer {
   FlutterOpenGLRenderer* renderer = [[FlutterOpenGLRenderer alloc] initWithFlutterEngine:engine];
   id mockFlutterView = OCMClassMock([FlutterView class]);
   [(FlutterView*)[mockFlutterView expect] present];
-  [renderer setFlutterView:mockFlutterView];
   [renderer openGLContext];
-  [renderer present];
+  [renderer present:mockFlutterView];
 }
 
 TEST(FlutterOpenGLRenderer, FBOReturnedByFlutterView) {
@@ -131,9 +130,8 @@ - (nullable instancetype)initWithGLRenderer {
   frameInfo.size = dimensions;
   CGSize size = CGSizeMake(dimensions.width, dimensions.height);
   [[mockFlutterView expect] backingStoreForSize:size];
-  [renderer setFlutterView:mockFlutterView];
   [renderer openGLContext];
-  [renderer fboForFrameInfo:&frameInfo];
+  [renderer fboForView:mockFlutterView frameInfo:&frameInfo];
 }
 
 }  // namespace flutter::testing
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
index 8f88964b38c60..8cf45aa2f24fb 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
@@ -19,24 +19,19 @@
  */
 - (nullable instancetype)initWithFlutterEngine:(nonnull FlutterEngine*)flutterEngine;
 
-/**
- * Sets the FlutterView to render to.
- */
-- (void)setFlutterView:(nullable FlutterView*)view;
-
 /**
  * Creates a FlutterRendererConfig that renders using the appropriate backend.
  */
 - (FlutterRendererConfig)createRendererConfig;
 
 /**
- * Called by the engine when the context's buffers should be swapped.
+ * Called by the engine when the given view's buffers should be swapped.
  */
-- (BOOL)present;
+- (BOOL)present:(nonnull FlutterView*)view;
 
 /**
  * Tells the renderer that there is no Flutter content available for this frame.
  */
-- (void)presentWithoutContent;
+- (void)presentWithoutContent:(nonnull FlutterView*)view;
 
 @end

From 067ed3e99f0a221a8846bd3dd801f5b7ae0596b7 Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Tue, 4 Oct 2022 10:11:09 -0700
Subject: [PATCH 02/15] Format

---
 .../darwin/macos/framework/Source/FlutterMetalRenderer.mm       | 2 +-
 .../darwin/macos/framework/Source/FlutterOpenGLRenderer.mm      | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
index 8ab7a33fea3c6..8308783a4ebb0 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
@@ -16,7 +16,7 @@ static FlutterMetalTexture OnGetNextDrawable(FlutterEngine* engine,
                                              const FlutterFrameInfo* frameInfo) {
   FlutterViewController* viewController = engine.viewController;
   if (viewController == nil) {
-    return FlutterMetalTexture{}; // TODO
+    return FlutterMetalTexture{};  // TODO
   }
   CGSize size = CGSizeMake(frameInfo->size.width, frameInfo->size.height);
   FlutterMetalRenderer* metalRenderer = reinterpret_cast<FlutterMetalRenderer*>(engine.renderer);
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
index 1c695e813eb90..bb019b112a71a 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
@@ -30,7 +30,7 @@ static bool OnPresent(FlutterEngine* engine) {
 static uint32_t OnFBO(FlutterEngine* engine, const FlutterFrameInfo* info) {
   FlutterViewController* viewController = engine.viewController;
   if (viewController == nil) {
-    return -1; // TODO
+    return -1;  // TODO
   }
   FlutterOpenGLRenderer* openGLRenderer = reinterpret_cast<FlutterOpenGLRenderer*>(engine.renderer);
   return [openGLRenderer fboForView:viewController.flutterView frameInfo:info];

From 8c577ac213590c0331900d3cf8605f3f60dfffda Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Thu, 3 Nov 2022 17:23:42 -0700
Subject: [PATCH 03/15] TODO comments

---
 .../darwin/macos/framework/Source/FlutterEngine.mm  |  3 +++
 .../macos/framework/Source/FlutterMetalRenderer.mm  |  6 ++++++
 .../macos/framework/Source/FlutterOpenGLRenderer.mm | 13 ++++++-------
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm b/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
index 70a5f33667181..e931ac31f5d5d 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
@@ -448,6 +448,9 @@ - (FlutterCompositor*)createFlutterCompositor {
         std::make_unique<flutter::FlutterGLCompositor>(_viewProvider, openGLRenderer.openGLContext);
   }
   _macOSCompositor->SetPresentCallback([weakSelf](bool has_flutter_content) {
+    // TODO(dkwingsmt): The renderer and the engine only support single-view for
+    // now. As more classes are gradually converted to multi-view, it should get
+    // the view ID from somewhere, and accordingly pick the correct view.
     FlutterView* view = weakSelf.viewController.flutterView;
     if (has_flutter_content) {
       return [weakSelf.renderer present:view] == YES;
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
index c74ffa734c215..430a1ad8a32d8 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
@@ -14,6 +14,9 @@
 
 static FlutterMetalTexture OnGetNextDrawable(FlutterEngine* engine,
                                              const FlutterFrameInfo* frameInfo) {
+  // TODO(dkwingsmt): The renderer only supports single-view for now. As more
+  // classes are gradually converted to multi-view, it should get the view ID
+  // from somewhere, and accordingly pick the correct view from the engine.
   FlutterViewController* viewController = engine.viewController;
   if (viewController == nil) {
     return FlutterMetalTexture{};  // TODO
@@ -24,6 +27,9 @@ static FlutterMetalTexture OnGetNextDrawable(FlutterEngine* engine,
 }
 
 static bool OnPresentDrawable(FlutterEngine* engine, const FlutterMetalTexture* texture) {
+  // TODO(dkwingsmt): The renderer only supports single-view for now. As more
+  // classes are gradually converted to multi-view, it should get the view ID
+  // from somewhere, and accordingly pick the correct view from the engine.
   FlutterViewController* viewController = engine.viewController;
   if (viewController == nil) {
     return false;
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
index bb019b112a71a..5add88ca062e2 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
@@ -20,6 +20,9 @@ static bool OnClearCurrent(FlutterEngine* engine) {
 }
 
 static bool OnPresent(FlutterEngine* engine) {
+  // TODO(dkwingsmt): The renderer only supports single-view for now. As more
+  // classes are gradually converted to multi-view, it should get the view ID
+  // from somewhere, and accordingly pick the correct view from the engine.
   FlutterViewController* viewController = engine.viewController;
   if (viewController == nil) {
     return false;
@@ -28,6 +31,9 @@ static bool OnPresent(FlutterEngine* engine) {
 }
 
 static uint32_t OnFBO(FlutterEngine* engine, const FlutterFrameInfo* info) {
+  // TODO(dkwingsmt): The renderer only supports single-view for now. As more
+  // classes are gradually converted to multi-view, it should get the view ID
+  // from somewhere, and accordingly pick the correct view from the engine.
   FlutterViewController* viewController = engine.viewController;
   if (viewController == nil) {
     return -1;  // TODO
@@ -68,13 +74,6 @@ - (instancetype)initWithFlutterEngine:(FlutterEngine*)flutterEngine {
   return self;
 }
 
-// - (void)setFlutterView:(FlutterView*)view {
-//   _flutterView = view;
-//   if (!view) {
-//     _resourceContext = nil;
-//   }
-// }
-
 - (BOOL)makeCurrent {
   if (!_openGLContext) {
     return false;

From fabcba0aef18adc0868e1db580a3deadd6dd8463 Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Mon, 7 Nov 2022 11:57:47 -0800
Subject: [PATCH 04/15] Fix compile

---
 .../darwin/macos/framework/Source/FlutterMetalRenderer.mm     | 4 ++--
 .../darwin/macos/framework/Source/FlutterOpenGLRenderer.mm    | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
index 430a1ad8a32d8..e081dcdaf7919 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
@@ -7,7 +7,7 @@
 
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterExternalTextureMetal.h"
-#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterView.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
 #include "flutter/shell/platform/embedder/embedder.h"
 
 #pragma mark - Static callbacks that require the engine.
@@ -49,7 +49,7 @@ static bool OnAcquireExternalTexture(FlutterEngine* engine,
 #pragma mark - FlutterMetalRenderer implementation
 
 @implementation FlutterMetalRenderer {
-  FlutterDarwinContextMetal* _darwinMetalContext;
+  FlutterDarwinContextMetalSkia* _darwinMetalContext;
 }
 
 - (instancetype)initWithFlutterEngine:(nonnull FlutterEngine*)flutterEngine {
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
index 5add88ca062e2..5c018893c4f9b 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
@@ -6,6 +6,7 @@
 
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterExternalTextureGL.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
 
 #pragma mark - Static methods for openGL callbacks that require the engine.
 

From 5ded32fc5f257f293da6411238944542fc853a87 Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Mon, 7 Nov 2022 13:31:45 -0800
Subject: [PATCH 05/15] Better empty indication

---
 shell/gpu/gpu_surface_gl_delegate.h                           | 2 ++
 shell/gpu/gpu_surface_gl_skia.cc                              | 4 ++++
 .../darwin/macos/framework/Source/FlutterMetalRenderer.mm     | 4 +++-
 .../darwin/macos/framework/Source/FlutterOpenGLRenderer.mm    | 4 +++-
 shell/platform/embedder/embedder.h                            | 2 ++
 5 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/shell/gpu/gpu_surface_gl_delegate.h b/shell/gpu/gpu_surface_gl_delegate.h
index f097cba2d0266..168270646c87f 100644
--- a/shell/gpu/gpu_surface_gl_delegate.h
+++ b/shell/gpu/gpu_surface_gl_delegate.h
@@ -26,6 +26,8 @@ struct GLFrameInfo {
 // the rendering backend after requesting a frame buffer object.
 struct GLFBOInfo {
   // The frame buffer's ID.
+  //
+  // This ID must not be 0, or this frame buffer is considered invalid.
   uint32_t fbo_id;
   // This boolean flags whether the returned FBO supports partial repaint.
   const bool partial_repaint_enabled;
diff --git a/shell/gpu/gpu_surface_gl_skia.cc b/shell/gpu/gpu_surface_gl_skia.cc
index 01be975ee831a..fd84f538f4c5e 100644
--- a/shell/gpu/gpu_surface_gl_skia.cc
+++ b/shell/gpu/gpu_surface_gl_skia.cc
@@ -182,6 +182,10 @@ bool GPUSurfaceGLSkia::CreateOrUpdateSurfaces(const SkISize& size) {
   GLFrameInfo frame_info = {static_cast<uint32_t>(size.width()),
                             static_cast<uint32_t>(size.height())};
   const GLFBOInfo fbo_info = delegate_->GLContextFBO(frame_info);
+  if (fbo_info.fbo_id == 0) {
+    FML_LOG(ERROR) << "Invalid FBO returned.";
+    return false;
+  }
   onscreen_surface = WrapOnscreenSurface(context_.get(),  // GL context
                                          size,            // root surface size
                                          fbo_info.fbo_id  // window FBO ID
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
index e081dcdaf7919..96739d2a2851a 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
@@ -19,7 +19,9 @@ static FlutterMetalTexture OnGetNextDrawable(FlutterEngine* engine,
   // from somewhere, and accordingly pick the correct view from the engine.
   FlutterViewController* viewController = engine.viewController;
   if (viewController == nil) {
-    return FlutterMetalTexture{};  // TODO
+    FML_LOG(WARNING) << "Can't create drawables on a null view controller.";
+    // FlutterMetalTexture has texture `null`, therefore is discarded.
+    return FlutterMetalTexture{};
   }
   CGSize size = CGSizeMake(frameInfo->size.width, frameInfo->size.height);
   FlutterMetalRenderer* metalRenderer = reinterpret_cast<FlutterMetalRenderer*>(engine.renderer);
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
index 5c018893c4f9b..9241b0bdf8cdf 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
@@ -37,7 +37,9 @@ static uint32_t OnFBO(FlutterEngine* engine, const FlutterFrameInfo* info) {
   // from somewhere, and accordingly pick the correct view from the engine.
   FlutterViewController* viewController = engine.viewController;
   if (viewController == nil) {
-    return -1;  // TODO
+    FML_LOG(WARNING) << "Can't create frame buffers on a null view controller.";
+    // The FBO has ID 0, therefore is discarded.
+    return 0;
   }
   FlutterOpenGLRenderer* openGLRenderer = reinterpret_cast<FlutterOpenGLRenderer*>(engine.renderer);
   return [openGLRenderer fboForView:viewController.flutterView frameInfo:info];
diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index c9e7bc27bb5a5..588a3e61ed35b 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -633,6 +633,8 @@ typedef struct {
   int64_t texture_id;
   /// Handle to the MTLTexture that is owned by the embedder. Engine will render
   /// the frame into this texture.
+  ///
+  /// The `texture` must not be null, or this texture is considered invalid.
   FlutterMetalTextureHandle texture;
   /// A baton that is not interpreted by the engine in any way. It will be given
   /// back to the embedder in the destruction callback below. Embedder resources

From 42b179a638301421b00efbad040ac023bacae2ee Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Mon, 7 Nov 2022 14:52:24 -0800
Subject: [PATCH 06/15] Change invalid ID to -1

---
 shell/gpu/gpu_surface_gl_skia.cc                            | 6 +++++-
 .../darwin/macos/framework/Source/FlutterOpenGLRenderer.mm  | 4 ++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/shell/gpu/gpu_surface_gl_skia.cc b/shell/gpu/gpu_surface_gl_skia.cc
index fd84f538f4c5e..eaea2035e46b2 100644
--- a/shell/gpu/gpu_surface_gl_skia.cc
+++ b/shell/gpu/gpu_surface_gl_skia.cc
@@ -182,7 +182,7 @@ bool GPUSurfaceGLSkia::CreateOrUpdateSurfaces(const SkISize& size) {
   GLFrameInfo frame_info = {static_cast<uint32_t>(size.width()),
                             static_cast<uint32_t>(size.height())};
   const GLFBOInfo fbo_info = delegate_->GLContextFBO(frame_info);
-  if (fbo_info.fbo_id == 0) {
+  if (fbo_info.fbo_id == -1) {
     FML_LOG(ERROR) << "Invalid FBO returned.";
     return false;
   }
@@ -295,6 +295,10 @@ bool GPUSurfaceGLSkia::PresentSurface(const SurfaceFrame& frame,
     // The FBO has changed, ask the delegate for the new FBO and do a surface
     // re-wrap.
     const GLFBOInfo fbo_info = delegate_->GLContextFBO(frame_info);
+    if (fbo_info.fbo_id == -1) {
+      FML_LOG(ERROR) << "Invalid FBO returned.";
+      return false;
+    }
     auto new_onscreen_surface =
         WrapOnscreenSurface(context_.get(),  // GL context
                             current_size,    // root surface size
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
index 9241b0bdf8cdf..805f20bdc93e4 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
@@ -38,8 +38,8 @@ static uint32_t OnFBO(FlutterEngine* engine, const FlutterFrameInfo* info) {
   FlutterViewController* viewController = engine.viewController;
   if (viewController == nil) {
     FML_LOG(WARNING) << "Can't create frame buffers on a null view controller.";
-    // The FBO has ID 0, therefore is discarded.
-    return 0;
+    // The FBO has ID -1, therefore is discarded.
+    return -1;
   }
   FlutterOpenGLRenderer* openGLRenderer = reinterpret_cast<FlutterOpenGLRenderer*>(engine.renderer);
   return [openGLRenderer fboForView:viewController.flutterView frameInfo:info];

From 3de585e730990e45e114b7f148cc1e93b86def58 Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Mon, 7 Nov 2022 14:56:01 -0800
Subject: [PATCH 07/15] fix doc

---
 shell/gpu/gpu_surface_gl_delegate.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shell/gpu/gpu_surface_gl_delegate.h b/shell/gpu/gpu_surface_gl_delegate.h
index 168270646c87f..de88619065e85 100644
--- a/shell/gpu/gpu_surface_gl_delegate.h
+++ b/shell/gpu/gpu_surface_gl_delegate.h
@@ -27,7 +27,7 @@ struct GLFrameInfo {
 struct GLFBOInfo {
   // The frame buffer's ID.
   //
-  // This ID must not be 0, or this frame buffer is considered invalid.
+  // This ID must not be -1, or this frame buffer is considered invalid.
   uint32_t fbo_id;
   // This boolean flags whether the returned FBO supports partial repaint.
   const bool partial_repaint_enabled;

From a462ef5111cfe08e6e5fa9e57436caf30368a1e7 Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Mon, 7 Nov 2022 18:09:25 -0800
Subject: [PATCH 08/15] Change to default view

---
 shell/gpu/gpu_surface_gl_skia.cc              |  8 ----
 .../framework/Source/FlutterMetalRenderer.h   |  5 +++
 .../framework/Source/FlutterMetalRenderer.mm  | 37 ++++++++--------
 .../framework/Source/FlutterOpenGLRenderer.h  |  5 +++
 .../framework/Source/FlutterOpenGLRenderer.mm | 43 ++++++++++---------
 .../macos/framework/Source/FlutterRenderer.h  |  5 ---
 6 files changed, 51 insertions(+), 52 deletions(-)

diff --git a/shell/gpu/gpu_surface_gl_skia.cc b/shell/gpu/gpu_surface_gl_skia.cc
index eaea2035e46b2..01be975ee831a 100644
--- a/shell/gpu/gpu_surface_gl_skia.cc
+++ b/shell/gpu/gpu_surface_gl_skia.cc
@@ -182,10 +182,6 @@ bool GPUSurfaceGLSkia::CreateOrUpdateSurfaces(const SkISize& size) {
   GLFrameInfo frame_info = {static_cast<uint32_t>(size.width()),
                             static_cast<uint32_t>(size.height())};
   const GLFBOInfo fbo_info = delegate_->GLContextFBO(frame_info);
-  if (fbo_info.fbo_id == -1) {
-    FML_LOG(ERROR) << "Invalid FBO returned.";
-    return false;
-  }
   onscreen_surface = WrapOnscreenSurface(context_.get(),  // GL context
                                          size,            // root surface size
                                          fbo_info.fbo_id  // window FBO ID
@@ -295,10 +291,6 @@ bool GPUSurfaceGLSkia::PresentSurface(const SurfaceFrame& frame,
     // The FBO has changed, ask the delegate for the new FBO and do a surface
     // re-wrap.
     const GLFBOInfo fbo_info = delegate_->GLContextFBO(frame_info);
-    if (fbo_info.fbo_id == -1) {
-      FML_LOG(ERROR) << "Invalid FBO returned.";
-      return false;
-    }
     auto new_onscreen_surface =
         WrapOnscreenSurface(context_.get(),  // GL context
                             current_size,    // root surface size
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
index 44a3d132ca363..66c44ae0f1dc9 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
@@ -14,6 +14,11 @@
  */
 @interface FlutterMetalRenderer : FlutterTextureRegistrar <FlutterRenderer>
 
+/**
+ * Intializes the renderer with the given FlutterEngine.
+ */
+- (nullable instancetype)initWithFlutterEngine:(nonnull FlutterEngine*)flutterEngine;
+
 /**
  * Interface to the system GPU. Used to issue all the rendering commands.
  */
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
index 96739d2a2851a..e6991822a91ba 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
@@ -12,31 +12,32 @@
 
 #pragma mark - Static callbacks that require the engine.
 
-static FlutterMetalTexture OnGetNextDrawable(FlutterEngine* engine,
-                                             const FlutterFrameInfo* frameInfo) {
-  // TODO(dkwingsmt): The renderer only supports single-view for now. As more
-  // classes are gradually converted to multi-view, it should get the view ID
-  // from somewhere, and accordingly pick the correct view from the engine.
-  FlutterViewController* viewController = engine.viewController;
-  if (viewController == nil) {
-    FML_LOG(WARNING) << "Can't create drawables on a null view controller.";
+static FlutterMetalTexture OnGetNextDrawableForDefaultView(FlutterEngine* engine,
+                                                           const FlutterFrameInfo* frameInfo) {
+  // TODO(dkwingsmt): This callback only supports single-view, therefore it only
+  // operates on the default view. To support multi-view, we need a new callback
+  // that also receives a view ID, or pass the ID via FlutterFrameInfo.
+  FlutterView* view = engine.viewController.flutterView;
+  if (view == nil) {
+    FML_LOG(WARNING) << "Can't create drawables on a non-existent view.";
     // FlutterMetalTexture has texture `null`, therefore is discarded.
     return FlutterMetalTexture{};
   }
   CGSize size = CGSizeMake(frameInfo->size.width, frameInfo->size.height);
   FlutterMetalRenderer* metalRenderer = reinterpret_cast<FlutterMetalRenderer*>(engine.renderer);
-  return [metalRenderer createTextureForView:viewController.flutterView size:size];
+  return [metalRenderer createTextureForView:view size:size];
 }
 
-static bool OnPresentDrawable(FlutterEngine* engine, const FlutterMetalTexture* texture) {
-  // TODO(dkwingsmt): The renderer only supports single-view for now. As more
-  // classes are gradually converted to multi-view, it should get the view ID
-  // from somewhere, and accordingly pick the correct view from the engine.
-  FlutterViewController* viewController = engine.viewController;
-  if (viewController == nil) {
+static bool OnPresentDrawableToDefaultView(FlutterEngine* engine,
+                                           const FlutterMetalTexture* texture) {
+  // TODO(dkwingsmt): This callback only supports single-view, therefore it only
+  // operates on the default view. To support multi-view, we need a new callback
+  // that also receives a view ID.
+  FlutterView* view = engine.viewController.flutterView;
+  if (view == nil) {
     return false;
   }
-  return [engine.renderer present:viewController.flutterView];
+  return [engine.renderer present:view];
 }
 
 static bool OnAcquireExternalTexture(FlutterEngine* engine,
@@ -82,9 +83,9 @@ - (FlutterRendererConfig)createRendererConfig {
       .metal.device = (__bridge FlutterMetalDeviceHandle)_device,
       .metal.present_command_queue = (__bridge FlutterMetalCommandQueueHandle)_commandQueue,
       .metal.get_next_drawable_callback =
-          reinterpret_cast<FlutterMetalTextureCallback>(OnGetNextDrawable),
+          reinterpret_cast<FlutterMetalTextureCallback>(OnGetNextDrawableForDefaultView),
       .metal.present_drawable_callback =
-          reinterpret_cast<FlutterMetalPresentCallback>(OnPresentDrawable),
+          reinterpret_cast<FlutterMetalPresentCallback>(OnPresentDrawableToDefaultView),
       .metal.external_texture_frame_callback =
           reinterpret_cast<FlutterMetalTextureFrameCallback>(OnAcquireExternalTexture),
   };
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
index 95999adc41f25..aef26cfbca076 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
@@ -13,6 +13,11 @@
  */
 @interface FlutterOpenGLRenderer : FlutterTextureRegistrar <FlutterRenderer>
 
+/**
+ * Intializes the renderer with the given FlutterEngine.
+ */
+- (nullable instancetype)initWithFlutterEngine:(nonnull FlutterEngine*)flutterEngine;
+
 /**
  * The resource context used by the engine for texture uploads. FlutterViews associated with this
  * engine should be created to share with this context.
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
index 805f20bdc93e4..5c4bbb7e37f58 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
@@ -20,29 +20,29 @@ static bool OnClearCurrent(FlutterEngine* engine) {
   return [openGLRenderer clearCurrent];
 }
 
-static bool OnPresent(FlutterEngine* engine) {
-  // TODO(dkwingsmt): The renderer only supports single-view for now. As more
-  // classes are gradually converted to multi-view, it should get the view ID
-  // from somewhere, and accordingly pick the correct view from the engine.
-  FlutterViewController* viewController = engine.viewController;
-  if (viewController == nil) {
+static bool OnPresentToDefaultView(FlutterEngine* engine) {
+  // TODO(dkwingsmt): This callback only supports single-view, therefore it only
+  // operates on the default view. To support multi-view, we need a new callback
+  // that also receives a view ID.
+  FlutterView* view = engine.viewController.flutterView;
+  if (view == nil) {
     return false;
   }
-  return [engine.renderer present:viewController.flutterView];
-}
-
-static uint32_t OnFBO(FlutterEngine* engine, const FlutterFrameInfo* info) {
-  // TODO(dkwingsmt): The renderer only supports single-view for now. As more
-  // classes are gradually converted to multi-view, it should get the view ID
-  // from somewhere, and accordingly pick the correct view from the engine.
-  FlutterViewController* viewController = engine.viewController;
-  if (viewController == nil) {
-    FML_LOG(WARNING) << "Can't create frame buffers on a null view controller.";
-    // The FBO has ID -1, therefore is discarded.
-    return -1;
+  return [engine.renderer present:view];
+}
+
+static uint32_t OnFBOForDefaultView(FlutterEngine* engine, const FlutterFrameInfo* info) {
+  // TODO(dkwingsmt): This callback only supports single-view, therefore it only
+  // operates on the default view. To support multi-view, we need a new callback
+  // that also receives a view ID, or pass the ID via FlutterFrameInfo.
+  FlutterView* view = engine.viewController.flutterView;
+  if (view == nil) {
+    // This callback does not have a proper way to report error, since we
+    // haven't defined an "invalid" FBO ID.
+    FML_LOG(WARNING) << "Can't create frame buffers on a non-existent view.";
   }
   FlutterOpenGLRenderer* openGLRenderer = reinterpret_cast<FlutterOpenGLRenderer*>(engine.renderer);
-  return [openGLRenderer fboForView:viewController.flutterView frameInfo:info];
+  return [openGLRenderer fboForView:view frameInfo:info];
 }
 
 static bool OnMakeResourceCurrent(FlutterEngine* engine) {
@@ -153,8 +153,9 @@ - (FlutterRendererConfig)createRendererConfig {
       .open_gl.struct_size = sizeof(FlutterOpenGLRendererConfig),
       .open_gl.make_current = reinterpret_cast<BoolCallback>(OnMakeCurrent),
       .open_gl.clear_current = reinterpret_cast<BoolCallback>(OnClearCurrent),
-      .open_gl.present = reinterpret_cast<BoolCallback>(OnPresent),
-      .open_gl.fbo_with_frame_info_callback = reinterpret_cast<UIntFrameInfoCallback>(OnFBO),
+      .open_gl.present = reinterpret_cast<BoolCallback>(OnPresentToDefaultView),
+      .open_gl.fbo_with_frame_info_callback =
+          reinterpret_cast<UIntFrameInfoCallback>(OnFBOForDefaultView),
       .open_gl.fbo_reset_after_present = true,
       .open_gl.make_resource_current = reinterpret_cast<BoolCallback>(OnMakeResourceCurrent),
       .open_gl.gl_external_texture_frame_callback =
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
index 8cf45aa2f24fb..32e84da2f4d9d 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
@@ -14,11 +14,6 @@
  */
 @protocol FlutterRenderer <FlutterTextureRegistry, FlutterTextureRegistrarDelegate>
 
-/**
- * Intializes the renderer with the given FlutterEngine.
- */
-- (nullable instancetype)initWithFlutterEngine:(nonnull FlutterEngine*)flutterEngine;
-
 /**
  * Creates a FlutterRendererConfig that renders using the appropriate backend.
  */

From 593b0c5f6efeaf63ddab7447fea5c8bd2bcf2c8f Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Mon, 7 Nov 2022 18:34:57 -0800
Subject: [PATCH 09/15] Better doc

---
 shell/gpu/gpu_surface_gl_delegate.h                          | 2 --
 .../platform/darwin/macos/framework/Headers/FlutterEngine.h  | 5 ++++-
 .../darwin/macos/framework/Source/FlutterMetalRenderer.h     | 5 -----
 .../darwin/macos/framework/Source/FlutterOpenGLRenderer.h    | 5 -----
 .../darwin/macos/framework/Source/FlutterOpenGLRenderer.mm   | 4 ++--
 .../platform/darwin/macos/framework/Source/FlutterRenderer.h | 5 +++++
 6 files changed, 11 insertions(+), 15 deletions(-)

diff --git a/shell/gpu/gpu_surface_gl_delegate.h b/shell/gpu/gpu_surface_gl_delegate.h
index de88619065e85..f097cba2d0266 100644
--- a/shell/gpu/gpu_surface_gl_delegate.h
+++ b/shell/gpu/gpu_surface_gl_delegate.h
@@ -26,8 +26,6 @@ struct GLFrameInfo {
 // the rendering backend after requesting a frame buffer object.
 struct GLFBOInfo {
   // The frame buffer's ID.
-  //
-  // This ID must not be -1, or this frame buffer is considered invalid.
   uint32_t fbo_id;
   // This boolean flags whether the returned FBO supports partial repaint.
   const bool partial_repaint_enabled;
diff --git a/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h b/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h
index 12ead38f104f4..20ec48be51e19 100644
--- a/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h
+++ b/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h
@@ -63,7 +63,10 @@ FLUTTER_DARWIN_EXPORT
 - (BOOL)runWithEntrypoint:(nullable NSString*)entrypoint;
 
 /**
- * The `FlutterViewController` associated with this engine, if any.
+ * The default `FlutterViewController` associated with this engine, if any.
+ *
+ * The default view always has ID 0, and is the view operated by the APIs that
+ * do not have a view ID specified.
  */
 @property(nonatomic, nullable, weak) FlutterViewController* viewController;
 
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
index 66c44ae0f1dc9..44a3d132ca363 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
@@ -14,11 +14,6 @@
  */
 @interface FlutterMetalRenderer : FlutterTextureRegistrar <FlutterRenderer>
 
-/**
- * Intializes the renderer with the given FlutterEngine.
- */
-- (nullable instancetype)initWithFlutterEngine:(nonnull FlutterEngine*)flutterEngine;
-
 /**
  * Interface to the system GPU. Used to issue all the rendering commands.
  */
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
index aef26cfbca076..95999adc41f25 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
@@ -13,11 +13,6 @@
  */
 @interface FlutterOpenGLRenderer : FlutterTextureRegistrar <FlutterRenderer>
 
-/**
- * Intializes the renderer with the given FlutterEngine.
- */
-- (nullable instancetype)initWithFlutterEngine:(nonnull FlutterEngine*)flutterEngine;
-
 /**
  * The resource context used by the engine for texture uploads. FlutterViews associated with this
  * engine should be created to share with this context.
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
index 5c4bbb7e37f58..a6f9a0cacc18d 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
@@ -37,8 +37,8 @@ static uint32_t OnFBOForDefaultView(FlutterEngine* engine, const FlutterFrameInf
   // that also receives a view ID, or pass the ID via FlutterFrameInfo.
   FlutterView* view = engine.viewController.flutterView;
   if (view == nil) {
-    // This callback does not have a proper way to report error, since we
-    // haven't defined an "invalid" FBO ID.
+    // This callback does not have a proper way to report error, since there's
+    // no way to label the returned integer as invalid.
     FML_LOG(WARNING) << "Can't create frame buffers on a non-existent view.";
   }
   FlutterOpenGLRenderer* openGLRenderer = reinterpret_cast<FlutterOpenGLRenderer*>(engine.renderer);
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
index 32e84da2f4d9d..8cf45aa2f24fb 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
@@ -14,6 +14,11 @@
  */
 @protocol FlutterRenderer <FlutterTextureRegistry, FlutterTextureRegistrarDelegate>
 
+/**
+ * Intializes the renderer with the given FlutterEngine.
+ */
+- (nullable instancetype)initWithFlutterEngine:(nonnull FlutterEngine*)flutterEngine;
+
 /**
  * Creates a FlutterRendererConfig that renders using the appropriate backend.
  */

From 187be453cd2bb456dbde33d266bf3a760ce5ea19 Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Tue, 8 Nov 2022 10:03:26 -0800
Subject: [PATCH 10/15] Update doc of FlutterFrameInfo

---
 shell/platform/embedder/embedder.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index 588a3e61ed35b..a5e032c7f2ed6 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -448,7 +448,9 @@ typedef struct {
 /// This information is passed to the embedder when requesting a frame buffer
 /// object.
 ///
-/// See: \ref FlutterOpenGLRendererConfig.fbo_with_frame_info_callback.
+/// See: \ref FlutterOpenGLRendererConfig.fbo_with_frame_info_callback,
+/// \ref FlutterMetalRendererConfig.get_next_drawable_callback,
+/// and \ref FlutterVulkanRendererConfig.get_next_image_callback.
 typedef struct {
   /// The size of this struct. Must be sizeof(FlutterFrameInfo).
   size_t struct_size;

From f17ce1dffeee4fa4d287fa0d045675d13735c54e Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Tue, 8 Nov 2022 12:33:19 -0800
Subject: [PATCH 11/15] Change to ID

---
 .../macos/framework/Source/FlutterEngine.mm   | 12 +++---
 .../framework/Source/FlutterMetalRenderer.h   |  2 +-
 .../framework/Source/FlutterMetalRenderer.mm  | 43 +++++++++++--------
 .../Source/FlutterMetalRendererTest.mm        | 14 +++++-
 .../framework/Source/FlutterOpenGLRenderer.h  |  2 +-
 .../framework/Source/FlutterOpenGLRenderer.mm | 41 +++++++++++-------
 .../Source/FlutterOpenGLRendererTest.mm       | 17 +++++++-
 .../macos/framework/Source/FlutterRenderer.h  |  4 +-
 8 files changed, 88 insertions(+), 47 deletions(-)

diff --git a/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm b/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
index 160d6484428c0..5758f38a1eefa 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
@@ -446,14 +446,14 @@ - (FlutterCompositor*)createFlutterCompositor {
         std::make_unique<flutter::FlutterGLCompositor>(_viewProvider, openGLRenderer.openGLContext);
   }
   _macOSCompositor->SetPresentCallback([weakSelf](bool has_flutter_content) {
-    // TODO(dkwingsmt): The renderer and the engine only support single-view for
-    // now. As more classes are gradually converted to multi-view, it should get
-    // the view ID from somewhere, and accordingly pick the correct view.
-    FlutterView* view = weakSelf.viewController.flutterView;
+    // TODO(dkwingsmt): The compositor only supports single-view for now. As
+    // more classes are gradually converted to multi-view, it should get the
+    // view ID from somewhere.
+    uint64_t viewId = 0;
     if (has_flutter_content) {
-      return [weakSelf.renderer present:view] == YES;
+      return [weakSelf.renderer present:viewId] == YES;
     } else {
-      [weakSelf.renderer presentWithoutContent:view];
+      [weakSelf.renderer presentWithoutContent:viewId];
       return true;
     }
   });
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
index 44a3d132ca363..1768ba7cce8f5 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h
@@ -27,7 +27,7 @@
 /**
  * Creates a Metal texture for the given view with the given size.
  */
-- (FlutterMetalTexture)createTextureForView:(nonnull FlutterView*)view size:(CGSize)size;
+- (FlutterMetalTexture)createTextureForView:(uint64_t)viewId size:(CGSize)size;
 
 /**
  * Populates the texture registry with the provided metalTexture.
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
index e6991822a91ba..42ddb24822c32 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
@@ -8,6 +8,7 @@
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterExternalTextureMetal.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"
 
 #pragma mark - Static callbacks that require the engine.
@@ -17,27 +18,19 @@ static FlutterMetalTexture OnGetNextDrawableForDefaultView(FlutterEngine* engine
   // TODO(dkwingsmt): This callback only supports single-view, therefore it only
   // operates on the default view. To support multi-view, we need a new callback
   // that also receives a view ID, or pass the ID via FlutterFrameInfo.
-  FlutterView* view = engine.viewController.flutterView;
-  if (view == nil) {
-    FML_LOG(WARNING) << "Can't create drawables on a non-existent view.";
-    // FlutterMetalTexture has texture `null`, therefore is discarded.
-    return FlutterMetalTexture{};
-  }
+  uint64_t viewId = 0;
   CGSize size = CGSizeMake(frameInfo->size.width, frameInfo->size.height);
   FlutterMetalRenderer* metalRenderer = reinterpret_cast<FlutterMetalRenderer*>(engine.renderer);
-  return [metalRenderer createTextureForView:view size:size];
+  return [metalRenderer createTextureForView:viewId size:size];
 }
 
-static bool OnPresentDrawableToDefaultView(FlutterEngine* engine,
+static bool OnPresentDrawableOfDefaultView(FlutterEngine* engine,
                                            const FlutterMetalTexture* texture) {
   // TODO(dkwingsmt): This callback only supports single-view, therefore it only
   // operates on the default view. To support multi-view, we need a new callback
   // that also receives a view ID.
-  FlutterView* view = engine.viewController.flutterView;
-  if (view == nil) {
-    return false;
-  }
-  return [engine.renderer present:view];
+  uint64_t viewId = 0;
+  return [engine.renderer present:viewId];
 }
 
 static bool OnAcquireExternalTexture(FlutterEngine* engine,
@@ -52,12 +45,14 @@ static bool OnAcquireExternalTexture(FlutterEngine* engine,
 #pragma mark - FlutterMetalRenderer implementation
 
 @implementation FlutterMetalRenderer {
+  FlutterViewEngineProvider* _viewProvider;
   FlutterDarwinContextMetalSkia* _darwinMetalContext;
 }
 
 - (instancetype)initWithFlutterEngine:(nonnull FlutterEngine*)flutterEngine {
   self = [super initWithDelegate:self engine:flutterEngine];
   if (self) {
+    _viewProvider = [[FlutterViewEngineProvider alloc] initWithEngine:flutterEngine];
     _device = MTLCreateSystemDefaultDevice();
     if (!_device) {
       NSLog(@"Could not acquire Metal device.");
@@ -85,7 +80,7 @@ - (FlutterRendererConfig)createRendererConfig {
       .metal.get_next_drawable_callback =
           reinterpret_cast<FlutterMetalTextureCallback>(OnGetNextDrawableForDefaultView),
       .metal.present_drawable_callback =
-          reinterpret_cast<FlutterMetalPresentCallback>(OnPresentDrawableToDefaultView),
+          reinterpret_cast<FlutterMetalPresentCallback>(OnPresentDrawableOfDefaultView),
       .metal.external_texture_frame_callback =
           reinterpret_cast<FlutterMetalTextureFrameCallback>(OnAcquireExternalTexture),
   };
@@ -94,7 +89,13 @@ - (FlutterRendererConfig)createRendererConfig {
 
 #pragma mark - Embedder callback implementations.
 
-- (FlutterMetalTexture)createTextureForView:(FlutterView*)view size:(CGSize)size {
+- (FlutterMetalTexture)createTextureForView:(uint64_t)viewId size:(CGSize)size {
+  FlutterView* view = [_viewProvider getView:viewId];
+  if (view == nil) {
+    FML_LOG(WARNING) << "Can't create texture on a non-existent view.";
+    // FlutterMetalTexture has texture `null`, therefore is discarded.
+    return FlutterMetalTexture{};
+  }
   FlutterMetalRenderBackingStore* backingStore =
       (FlutterMetalRenderBackingStore*)[view backingStoreForSize:size];
   id<MTLTexture> texture = backingStore.texture;
@@ -105,12 +106,20 @@ - (FlutterMetalTexture)createTextureForView:(FlutterView*)view size:(CGSize)size
   return embedderTexture;
 }
 
-- (BOOL)present:(FlutterView*)view {
+- (BOOL)present:(uint64_t)viewId {
+  FlutterView* view = [_viewProvider getView:viewId];
+  if (view == nil) {
+    return NO;
+  }
   [view present];
   return YES;
 }
 
-- (void)presentWithoutContent:(FlutterView*)view {
+- (void)presentWithoutContent:(uint64_t)viewId {
+  FlutterView* view = [_viewProvider getView:viewId];
+  if (view == nil) {
+    return;
+  }
   [view presentWithoutContent];
 }
 
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm
index b1b84295a4992..ece1339a5c22e 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm
@@ -9,6 +9,7 @@
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterView.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
 #include "flutter/shell/platform/embedder/embedder.h"
 #include "flutter/shell/platform/embedder/test_utils/proc_table_replacement.h"
 #include "flutter/testing/testing.h"
@@ -24,20 +25,29 @@
              ICUDataPath:[fixtures stringByAppendingString:@"/icudtl.dat"]];
   return [[FlutterEngine alloc] initWithName:@"test" project:project allowHeadlessExecution:true];
 }
+
+void SetEngineDefaultView(FlutterEngine* engine, id flutterView) {
+  id mockFlutterViewController = OCMClassMock([FlutterViewController class]);
+  OCMStub([mockFlutterViewController flutterView]).andReturn(flutterView);
+  [engine setViewController:mockFlutterViewController];
+}
+
 }  // namespace
 
 TEST(FlutterMetalRenderer, PresentDelegatesToFlutterView) {
   FlutterEngine* engine = CreateTestEngine();
   FlutterMetalRenderer* renderer = [[FlutterMetalRenderer alloc] initWithFlutterEngine:engine];
   id mockFlutterView = OCMClassMock([FlutterView class]);
+  SetEngineDefaultView(engine, mockFlutterView);
   [(FlutterView*)[mockFlutterView expect] present];
-  [renderer present:mockFlutterView];
+  [renderer present:0];
 }
 
 TEST(FlutterMetalRenderer, TextureReturnedByFlutterView) {
   FlutterEngine* engine = CreateTestEngine();
   FlutterMetalRenderer* renderer = [[FlutterMetalRenderer alloc] initWithFlutterEngine:engine];
   id mockFlutterView = OCMClassMock([FlutterView class]);
+  SetEngineDefaultView(engine, mockFlutterView);
   FlutterFrameInfo frameInfo;
   frameInfo.struct_size = sizeof(FlutterFrameInfo);
   FlutterUIntSize dimensions;
@@ -46,7 +56,7 @@
   frameInfo.size = dimensions;
   CGSize size = CGSizeMake(dimensions.width, dimensions.height);
   [[mockFlutterView expect] backingStoreForSize:size];
-  [renderer createTextureForView:mockFlutterView size:size];
+  [renderer createTextureForView:0 size:size];
 }
 
 }  // namespace flutter::testing
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
index 95999adc41f25..d2817134d01ba 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
@@ -37,7 +37,7 @@
 /**
  * Called by the engine when framebuffer object ID is requested.
  */
-- (uint32_t)fboForView:(nonnull FlutterView*)view frameInfo:(nonnull const FlutterFrameInfo*)info;
+- (uint32_t)fboForView:(uint64_t)viewId frameInfo:(nonnull const FlutterFrameInfo*)info;
 
 /**
  * Makes the resource context the current context.
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
index a6f9a0cacc18d..c05784a51bbc2 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
@@ -7,6 +7,7 @@
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterExternalTextureGL.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewEngineProvider.h"
 
 #pragma mark - Static methods for openGL callbacks that require the engine.
 
@@ -24,25 +25,17 @@ static bool OnPresentToDefaultView(FlutterEngine* engine) {
   // TODO(dkwingsmt): This callback only supports single-view, therefore it only
   // operates on the default view. To support multi-view, we need a new callback
   // that also receives a view ID.
-  FlutterView* view = engine.viewController.flutterView;
-  if (view == nil) {
-    return false;
-  }
-  return [engine.renderer present:view];
+  uint64_t viewId = 0;
+  return [engine.renderer present:viewId];
 }
 
 static uint32_t OnFBOForDefaultView(FlutterEngine* engine, const FlutterFrameInfo* info) {
   // TODO(dkwingsmt): This callback only supports single-view, therefore it only
   // operates on the default view. To support multi-view, we need a new callback
   // that also receives a view ID, or pass the ID via FlutterFrameInfo.
-  FlutterView* view = engine.viewController.flutterView;
-  if (view == nil) {
-    // This callback does not have a proper way to report error, since there's
-    // no way to label the returned integer as invalid.
-    FML_LOG(WARNING) << "Can't create frame buffers on a non-existent view.";
-  }
+  uint64_t viewId = 0;
   FlutterOpenGLRenderer* openGLRenderer = reinterpret_cast<FlutterOpenGLRenderer*>(engine.renderer);
-  return [openGLRenderer fboForView:view frameInfo:info];
+  return [openGLRenderer fboForView:viewId frameInfo:info];
 }
 
 static bool OnMakeResourceCurrent(FlutterEngine* engine) {
@@ -63,6 +56,8 @@ static bool OnAcquireExternalTexture(FlutterEngine* engine,
 #pragma mark - FlutterOpenGLRenderer implementation.
 
 @implementation FlutterOpenGLRenderer {
+  FlutterViewEngineProvider* _viewProvider;
+
   // The context provided to the Flutter engine for rendering to the FlutterView. This is lazily
   // created during initialization of the FlutterView. This is used to render content into the
   // FlutterView.
@@ -74,6 +69,9 @@ @implementation FlutterOpenGLRenderer {
 
 - (instancetype)initWithFlutterEngine:(FlutterEngine*)flutterEngine {
   self = [super initWithDelegate:self engine:flutterEngine];
+  if (self) {
+    _viewProvider = [[FlutterViewEngineProvider alloc] initWithEngine:flutterEngine];
+  }
   return self;
 }
 
@@ -90,19 +88,30 @@ - (BOOL)clearCurrent {
   return true;
 }
 
-- (BOOL)present:(FlutterView*)view {
-  if (!_openGLContext) {
+- (BOOL)present:(uint64_t)viewId {
+  FlutterView* view = [_viewProvider getView:viewId];
+  if (!_openGLContext || view == nil) {
     return NO;
   }
   [view present];
   return YES;
 }
 
-- (void)presentWithoutContent:(FlutterView*)view {
+- (void)presentWithoutContent:(uint64_t)viewId {
+  FlutterView* view = [_viewProvider getView:viewId];
+  if (view == nil) {
+    return;
+  }
   [view presentWithoutContent];
 }
 
-- (uint32_t)fboForView:(FlutterView*)view frameInfo:(const FlutterFrameInfo*)info {
+- (uint32_t)fboForView:(uint64_t)viewId frameInfo:(const FlutterFrameInfo*)info {
+  FlutterView* view = [_viewProvider getView:viewId];
+  if (view == nil) {
+    // This method can't properly report errors, since there's no way to label
+    // the returned integer as invalid.
+    FML_LOG(ERROR) << "Can't create frame buffers on a non-existent view.";
+  }
   CGSize size = CGSizeMake(info->size.width, info->size.height);
   FlutterOpenGLRenderBackingStore* backingStore =
       reinterpret_cast<FlutterOpenGLRenderBackingStore*>([view backingStoreForSize:size]);
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRendererTest.mm b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRendererTest.mm
index ee33b524d1cdb..cbbd63dfd949c 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRendererTest.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRendererTest.mm
@@ -9,6 +9,7 @@
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterView.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
 #include "flutter/shell/platform/embedder/embedder.h"
 #include "flutter/shell/platform/embedder/test_utils/proc_table_replacement.h"
 #include "flutter/testing/testing.h"
@@ -44,6 +45,16 @@ - (nullable instancetype)initWithGLRenderer {
 
 namespace flutter::testing {
 
+namespace {
+
+void SetEngineDefaultView(FlutterEngine* engine, id flutterView) {
+  id mockFlutterViewController = OCMClassMock([FlutterViewController class]);
+  OCMStub([mockFlutterViewController flutterView]).andReturn(flutterView);
+  [engine setViewController:mockFlutterViewController];
+}
+
+}  // namespace
+
 TEST(FlutterOpenGLRenderer, RegisterExternalTexture) {
   FlutterEngine* engine = [[TestOpenGLEngine alloc] initWithGLRenderer];
   EXPECT_TRUE([engine runWithEntrypoint:@"main"]);
@@ -113,15 +124,17 @@ - (nullable instancetype)initWithGLRenderer {
   FlutterEngine* engine = [[TestOpenGLEngine alloc] initWithGLRenderer];
   FlutterOpenGLRenderer* renderer = [[FlutterOpenGLRenderer alloc] initWithFlutterEngine:engine];
   id mockFlutterView = OCMClassMock([FlutterView class]);
+  SetEngineDefaultView(engine, mockFlutterView);
   [(FlutterView*)[mockFlutterView expect] present];
   [renderer openGLContext];
-  [renderer present:mockFlutterView];
+  [renderer present:0];
 }
 
 TEST(FlutterOpenGLRenderer, FBOReturnedByFlutterView) {
   FlutterEngine* engine = [[TestOpenGLEngine alloc] initWithGLRenderer];
   FlutterOpenGLRenderer* renderer = [[FlutterOpenGLRenderer alloc] initWithFlutterEngine:engine];
   id mockFlutterView = OCMClassMock([FlutterView class]);
+  SetEngineDefaultView(engine, mockFlutterView);
   FlutterFrameInfo frameInfo;
   frameInfo.struct_size = sizeof(FlutterFrameInfo);
   FlutterUIntSize dimensions;
@@ -131,7 +144,7 @@ - (nullable instancetype)initWithGLRenderer {
   CGSize size = CGSizeMake(dimensions.width, dimensions.height);
   [[mockFlutterView expect] backingStoreForSize:size];
   [renderer openGLContext];
-  [renderer fboForView:mockFlutterView frameInfo:&frameInfo];
+  [renderer fboForView:0 frameInfo:&frameInfo];
 }
 
 }  // namespace flutter::testing
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
index 8cf45aa2f24fb..f977344a58baf 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
+++ b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
@@ -27,11 +27,11 @@
 /**
  * Called by the engine when the given view's buffers should be swapped.
  */
-- (BOOL)present:(nonnull FlutterView*)view;
+- (BOOL)present:(uint64_t)viewId;
 
 /**
  * Tells the renderer that there is no Flutter content available for this frame.
  */
-- (void)presentWithoutContent:(nonnull FlutterView*)view;
+- (void)presentWithoutContent:(uint64_t)viewId;
 
 @end

From 8e7c29ecec5065aa0e509c26b7cc17b2991a50fe Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Mon, 14 Nov 2022 11:35:24 -0800
Subject: [PATCH 12/15] Address comment

---
 shell/platform/darwin/macos/framework/Headers/FlutterEngine.h | 4 ++--
 shell/platform/darwin/macos/framework/Source/FlutterEngine.mm | 2 +-
 .../darwin/macos/framework/Source/FlutterMetalRenderer.mm     | 4 ++--
 .../darwin/macos/framework/Source/FlutterMetalRendererTest.mm | 4 ++--
 4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h b/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h
index 20ec48be51e19..49032f87d3a91 100644
--- a/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h
+++ b/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h
@@ -65,8 +65,8 @@ FLUTTER_DARWIN_EXPORT
 /**
  * The default `FlutterViewController` associated with this engine, if any.
  *
- * The default view always has ID 0, and is the view operated by the APIs that
- * do not have a view ID specified.
+ * The default view always has ID kFlutterDefaultViewId, and is the view
+ * operated by the APIs that do not have a view ID specified.
  */
 @property(nonatomic, nullable, weak) FlutterViewController* viewController;
 
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm b/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
index 0fcc6494b9009..2051c268f2084 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
@@ -434,7 +434,7 @@ - (FlutterCompositor*)createFlutterCompositor {
     // TODO(dkwingsmt): The compositor only supports single-view for now. As
     // more classes are gradually converted to multi-view, it should get the
     // view ID from somewhere.
-    uint64_t viewId = 0;
+    uint64_t viewId = kFlutterDefaultViewId;
     if (has_flutter_content) {
       return [weakSelf.renderer present:viewId] == YES;
     } else {
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
index 42ddb24822c32..87d3baad94758 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.mm
@@ -18,7 +18,7 @@ static FlutterMetalTexture OnGetNextDrawableForDefaultView(FlutterEngine* engine
   // TODO(dkwingsmt): This callback only supports single-view, therefore it only
   // operates on the default view. To support multi-view, we need a new callback
   // that also receives a view ID, or pass the ID via FlutterFrameInfo.
-  uint64_t viewId = 0;
+  uint64_t viewId = kFlutterDefaultViewId;
   CGSize size = CGSizeMake(frameInfo->size.width, frameInfo->size.height);
   FlutterMetalRenderer* metalRenderer = reinterpret_cast<FlutterMetalRenderer*>(engine.renderer);
   return [metalRenderer createTextureForView:viewId size:size];
@@ -29,7 +29,7 @@ static bool OnPresentDrawableOfDefaultView(FlutterEngine* engine,
   // TODO(dkwingsmt): This callback only supports single-view, therefore it only
   // operates on the default view. To support multi-view, we need a new callback
   // that also receives a view ID.
-  uint64_t viewId = 0;
+  uint64_t viewId = kFlutterDefaultViewId;
   return [engine.renderer present:viewId];
 }
 
diff --git a/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm b/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm
index ece1339a5c22e..9f4ca341fe60f 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterMetalRendererTest.mm
@@ -40,7 +40,7 @@ void SetEngineDefaultView(FlutterEngine* engine, id flutterView) {
   id mockFlutterView = OCMClassMock([FlutterView class]);
   SetEngineDefaultView(engine, mockFlutterView);
   [(FlutterView*)[mockFlutterView expect] present];
-  [renderer present:0];
+  [renderer present:kFlutterDefaultViewId];
 }
 
 TEST(FlutterMetalRenderer, TextureReturnedByFlutterView) {
@@ -56,7 +56,7 @@ void SetEngineDefaultView(FlutterEngine* engine, id flutterView) {
   frameInfo.size = dimensions;
   CGSize size = CGSizeMake(dimensions.width, dimensions.height);
   [[mockFlutterView expect] backingStoreForSize:size];
-  [renderer createTextureForView:0 size:size];
+  [renderer createTextureForView:kFlutterDefaultViewId size:size];
 }
 
 }  // namespace flutter::testing

From 6b9ca1bba47e8a30cf1dbcae235a72dce07e8f5d Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Mon, 14 Nov 2022 11:40:32 -0800
Subject: [PATCH 13/15] Fix comment

---
 shell/platform/embedder/embedder.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shell/platform/embedder/embedder.h b/shell/platform/embedder/embedder.h
index 23dda3a281ff3..e4fd8cc217490 100644
--- a/shell/platform/embedder/embedder.h
+++ b/shell/platform/embedder/embedder.h
@@ -636,7 +636,7 @@ typedef struct {
   /// Handle to the MTLTexture that is owned by the embedder. Engine will render
   /// the frame into this texture.
   ///
-  /// The `texture` must not be null, or this texture is considered invalid.
+  /// A NULL texture is considered invalid.
   FlutterMetalTextureHandle texture;
   /// A baton that is not interpreted by the engine in any way. It will be given
   /// back to the embedder in the destruction callback below. Embedder resources

From c4373ece6e5b51f0448dc2691da8cd9230371e65 Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Thu, 17 Nov 2022 11:02:09 -0800
Subject: [PATCH 14/15] To assertion

---
 shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm
index 33de0ffaef0c2..44e2b05236cff 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm
@@ -90,8 +90,8 @@ - (FlutterRendererConfig)createRendererConfig {
 
 - (FlutterMetalTexture)createTextureForView:(uint64_t)viewId size:(CGSize)size {
   FlutterView* view = [_viewProvider getView:viewId];
+  NSAssert(view != nil, "Can't create texture on a non-existent view 0x%x.", viewId);
   if (view == nil) {
-    FML_LOG(WARNING) << "Can't create texture on a non-existent view.";
     // FlutterMetalTexture has texture `null`, therefore is discarded.
     return FlutterMetalTexture{};
   }

From 9272daadc4b70062ba25241947488ef73864cf18 Mon Sep 17 00:00:00 2001
From: Tong Mu <dkwingsmt@gmail.com>
Date: Thu, 17 Nov 2022 11:32:42 -0800
Subject: [PATCH 15/15] Fix compile

---
 shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm
index 44e2b05236cff..d02de6c5c8eab 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm
@@ -90,7 +90,7 @@ - (FlutterRendererConfig)createRendererConfig {
 
 - (FlutterMetalTexture)createTextureForView:(uint64_t)viewId size:(CGSize)size {
   FlutterView* view = [_viewProvider getView:viewId];
-  NSAssert(view != nil, "Can't create texture on a non-existent view 0x%x.", viewId);
+  NSAssert(view != nil, @"Can't create texture on a non-existent view 0x%llx.", viewId);
   if (view == nil) {
     // FlutterMetalTexture has texture `null`, therefore is discarded.
     return FlutterMetalTexture{};