Reenable the FlutterEngine.Compositor test

Author: knopp

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

@@ -79,8 +79,6 @@
 void FlutterCompositor::PresentPlatformView(FlutterView* default_base_view,
                                             const FlutterLayer* layer,
                                             size_t layer_position) {
-  // TODO (https://github.com/flutter/flutter/issues/96668)
-  // once the issue is fixed, this check will pass.
   FML_DCHECK([[NSThread currentThread] isMainThread])
       << "Must be on the main thread to present platform views";
 
@@ -94,6 +92,7 @@
                                    layer->size.width / scale, layer->size.height / scale);
   if (platform_view.superview == nil) {
     [default_base_view addSubview:platform_view];
+    [default_base_view.layer addSublayer:platform_view.layer];
   }
   platform_view.layer.zPosition = layer_position;
 }

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

@@ -30,6 +30,20 @@ @interface FlutterEngine (Test)
 @property(nonatomic, readonly, nullable) flutter::FlutterCompositor* macOSCompositor;
 @end
 
+@interface TestPlatformViewFactory : NSObject <FlutterPlatformViewFactory>
+@end
+
+@implementation TestPlatformViewFactory
+- (nonnull NSView*)createWithViewIdentifier:(int64_t)viewId arguments:(nullable id)args {
+  if (viewId == 42) {
+    return [[NSView alloc] init];
+  } else {
+    return nil;
+  }
+}
+
+@end
+
 namespace flutter::testing {
 
 TEST_F(FlutterEngineTest, CanLaunch) {
@@ -447,9 +461,7 @@ @interface FlutterEngine (Test)
   ASSERT_TRUE(latch_called);
 }
 
-#if 0
-// TODO(iskakaushik): Enable after https://github.com/flutter/flutter/issues/96668 is fixed.
-TEST(FlutterEngine, DISABLED_Compositor) {
+TEST(FlutterEngine, Compositor) {
   NSString* fixtures = @(flutter::testing::GetFixturesPath());
   FlutterDartProject* project = [[FlutterDartProject alloc]
       initWithAssetsPath:fixtures
@@ -463,27 +475,28 @@ @interface FlutterEngine (Test)
 
   EXPECT_TRUE([engine runWithEntrypoint:@"canCompositePlatformViews"]);
 
-  // Latch to ensure the entire layer tree has been generated and presented.
-  fml::AutoResetWaitableEvent latch;
-  auto compositor = engine.macOSCompositor;
-  compositor->SetPresentCallback([&](bool has_flutter_content) {
-    latch.Signal();
-    return true;
-  });
-  latch.Wait();
+  [engine.platformViewController registerViewFactory:[[TestPlatformViewFactory alloc] init]
+                                              withId:@"factory_id"];
+  [engine.platformViewController
+      handleMethodCall:[FlutterMethodCall methodCallWithMethodName:@"create"
+                                                         arguments:@{
+                                                           @"id" : @(42),
+                                                           @"viewType" : @"factory_id",
+                                                         }]
+                result:^(id result){
+                }];
+
+  [viewController.flutterView.threadSynchronizer blockUntilFrameAvailable];
 
   CALayer* rootLayer = viewController.flutterView.layer;
 
   // There are three layers total - the root layer and two sublayers.
-  // This test will need to be updated when PlatformViews are supported, as
-  // there are two PlatformView layers in this test.
-  EXPECT_EQ(rootLayer.sublayers.count, 2u);
+  EXPECT_EQ(rootLayer.sublayers.count, 3u);
 
   // TODO(gw280): add support for screenshot tests in this test harness
 
   [engine shutDownEngine];
-}
-#endif
+}  // namespace flutter::testing
 
 TEST(FlutterEngine, DartEntrypointArguments) {
   NSString* fixtures = @(flutter::testing::GetFixturesPath());

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

@@ -53,6 +53,8 @@ - (void)onCreateWithViewID:(int64_t)viewId
   }
 
   NSView* platform_view = [factory createWithViewIdentifier:viewId arguments:nil];
+  // Force view to be layer-backed.
+  [platform_view setWantsLayer:YES];
   _platformViews[viewId] = platform_view;
   result(nil);
 }

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

@@ -5,6 +5,12 @@
  */
 @interface FlutterThreadSynchronizer : NSObject
 
+/**
+ * Blocks current thread until there is frame available.
+ * Used in FlutterEngineTest.
+ */
+- (void)blockUntilFrameAvailable;
+
 /**
  * Called from platform thread. Blocks until commit with given size (or empty)
  * is requested.

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

@@ -56,6 +56,19 @@ - (void)drain {
   _scheduledBlocks.clear();
 }
 
+- (void)blockUntilFrameAvailable {
+  std::unique_lock<std::mutex> lock(_mutex);
+
+  _beginResizeWaiting = YES;
+
+  while (CGSizeEqualToSize(_contentSize, CGSizeZero) && !_shuttingDown) {
+    _condBlockBeginResize.wait(lock);
+    [self drain];
+  }
+
+  _beginResizeWaiting = NO;
+}
+
 - (void)beginResize:(CGSize)size notify:(nonnull dispatch_block_t)notify {
   std::unique_lock<std::mutex> lock(_mutex);
 

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

@@ -5,6 +5,7 @@
 #import <Cocoa/Cocoa.h>
 
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterSurfaceManager.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterThreadSynchronizer.h"
 
 #include <stdint.h>
 
@@ -71,3 +72,13 @@ constexpr uint64_t kFlutterDefaultViewId = 0;
 - (void)setBackgroundColor:(nonnull NSColor*)color;
 
 @end
+
+@interface FlutterView (FlutterViewPrivate)
+
+/**
+ * Returns FlutterThreadSynchronizer for this view.
+ * Used for FlutterEngineTest.
+ */
+- (nonnull FlutterThreadSynchronizer*)threadSynchronizer;
+
+@end

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

@@ -45,6 +45,10 @@ - (FlutterSurfaceManager*)surfaceManager {
   return _surfaceManager;
 }
 
+- (FlutterThreadSynchronizer*)threadSynchronizer {
+  return _threadSynchronizer;
+}
+
 - (void)reshaped {
   CGSize scaledSize = [self convertSizeToBacking:self.bounds.size];
   [_threadSynchronizer beginResize:scaledSize