Address comment

Author: dkwingsmt

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;
 

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 {

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];
 }
 

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