iOS: Apply nullability annotations to FlutterPlatformViewsController (flutter/engine#56839)

Applies non-null by default annotations to
FlutterPlatformViewsController with opt-outs where necessary. Updates unit tests to create graphics contexts where requried.

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViewsController.h

@@ -23,24 +23,23 @@
 #import "flutter/shell/platform/darwin/ios/framework/Source/overlay_layer_pool.h"
 #import "flutter/shell/platform/darwin/ios/ios_context.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @class FlutterTouchInterceptingView;
 @class FlutterClippingMaskViewPool;
 
 @interface FlutterPlatformViewsController : NSObject
 
-- (id)init NS_DESIGNATED_INITIALIZER;
+- (instancetype)init NS_DESIGNATED_INITIALIZER;
 
 /// The task runner used to post rendering tasks to the platform thread.
 @property(nonatomic, assign) const fml::RefPtr<fml::TaskRunner>& taskRunner;
 
 /// The flutter view.
-@property(nonatomic, weak) UIView* flutterView;
+@property(nonatomic, weak) UIView* _Nullable flutterView;
 
 /// @brief The flutter view controller.
-@property(nonatomic, weak) UIViewController<FlutterViewResponder>* flutterViewController;
+@property(nonatomic, weak) UIViewController<FlutterViewResponder>* _Nullable flutterViewController;
-
-/// @brief Retrieve the view controller.
-- (UIViewController<FlutterViewResponder>*)flutterViewController;
 
 /// @brief set the factory used to construct embedded UI Views.
 - (void)registerViewFactory:(NSObject<FlutterPlatformViewFactory>*)factory
@@ -101,7 +100,7 @@
 /// Called from the raster thread.
 - (BOOL)submitFrame:(std::unique_ptr<flutter::SurfaceFrame>)frame
      withIosContext:(const std::shared_ptr<flutter::IOSContext>&)iosContext
-          grContext:(GrDirectContext*)grContext;
+          grContext:(GrDirectContext* _Nullable)grContext;
 
 /// @brief Handler for platform view message channels.
 - (void)onMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result;
@@ -130,7 +129,7 @@
 // If the `PlatformViewsController` does not contain any `FlutterPlatformView` object or
 // a `FlutterPlatformView` object associated with the view_id cannot be found, the method
 // returns nil.
-- (UIView*)platformViewForId:(int64_t)viewId;
+- (UIView* _Nullable)platformViewForId:(int64_t)viewId;
 
 // Composite the PlatformView with `viewId`.
 //
@@ -146,4 +145,6 @@
 
 @end
 
+NS_ASSUME_NONNULL_END
+
 #endif  // FLUTTER_SHELL_PLATFORM_DARWIN_IOS_FRAMEWORK_SOURCE_FLUTTERPLATFORMVIEWSCONTROLLER_H_

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViewsController.mm

@@ -705,6 +705,7 @@ static bool ClipRRectContainsPlatformViewBoundingRect(const SkRRect& clip_rrect,
 }
 
 - (flutter::DlCanvas*)compositeEmbeddedViewWithId:(int64_t)viewId {
+  FML_DCHECK(self.slices.find(viewId) != self.slices.end());
   return self.slices[viewId]->canvas();
 }
 

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViewsTest.mm

@@ -8,6 +8,8 @@
 #import <UIKit/UIKit.h>
 #import <XCTest/XCTest.h>
 
+#include <memory>
+
 #include "flutter/display_list/effects/dl_image_filters.h"
 #include "flutter/fml/synchronization/count_down_latch.h"
 #include "flutter/fml/thread.h"
@@ -17,6 +19,7 @@
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViewsController.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViews_Internal.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterTouchInterceptingView_Test.h"
+#include "flutter/shell/platform/darwin/ios/ios_context_noop.h"
 #include "flutter/shell/platform/darwin/ios/platform_view_ios.h"
 
 FLUTTER_ASSERT_ARC
@@ -3103,8 +3106,9 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
       [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return false; },
       [](const flutter::SurfaceFrame& surface_frame) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
-  XCTAssertFalse([flutterPlatformViewsController submitFrame:std::move(mock_surface)
+  XCTAssertFalse([flutterPlatformViewsController
-                                              withIosContext:nil
+         submitFrame:std::move(mock_surface)
+      withIosContext:std::make_shared<flutter::IOSContextNoop>()
            grContext:nil]);
 
   auto embeddedViewParams_2 =
@@ -3120,8 +3124,9 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
       [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return true; },
       [](const flutter::SurfaceFrame& surface_frame) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
-  XCTAssertTrue([flutterPlatformViewsController submitFrame:std::move(mock_surface_submit_true)
+  XCTAssertTrue([flutterPlatformViewsController
-                                             withIosContext:nil
+         submitFrame:std::move(mock_surface_submit_true)
+      withIosContext:std::make_shared<flutter::IOSContextNoop>()
            grContext:nil]);
 }
 
@@ -3328,9 +3333,9 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
       [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return true; },
       [](const flutter::SurfaceFrame& surface_frame) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
-
+  XCTAssertTrue([flutterPlatformViewsController
-  XCTAssertTrue([flutterPlatformViewsController submitFrame:std::move(mock_surface)
+         submitFrame:std::move(mock_surface)
-                                             withIosContext:nil
+      withIosContext:std::make_shared<flutter::IOSContextNoop>()
            grContext:nil]);
 
   // platform view is wrapped by touch interceptor, which itself is wrapped by clipping view.
@@ -3359,8 +3364,9 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
       [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return true; },
       [](const flutter::SurfaceFrame& surface_frame) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
-  XCTAssertTrue([flutterPlatformViewsController submitFrame:std::move(mock_surface)
+  XCTAssertTrue([flutterPlatformViewsController
-                                             withIosContext:nil
+         submitFrame:std::move(mock_surface)
+      withIosContext:std::make_shared<flutter::IOSContextNoop>()
            grContext:nil]);
 
   XCTAssertTrue([flutterView.subviews indexOfObject:clippingView1] >
@@ -3442,9 +3448,9 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
       [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return true; },
       [](const flutter::SurfaceFrame& surface_frame) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
-
+  XCTAssertTrue([flutterPlatformViewsController
-  XCTAssertTrue([flutterPlatformViewsController submitFrame:std::move(mock_surface)
+         submitFrame:std::move(mock_surface)
-                                             withIosContext:nil
+      withIosContext:std::make_shared<flutter::IOSContextNoop>()
            grContext:nil]);
 
   // platform view is wrapped by touch interceptor, which itself is wrapped by clipping view.
@@ -3473,9 +3479,9 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
       [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return true; },
       [](const flutter::SurfaceFrame& surface_frame) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
-
+  XCTAssertTrue([flutterPlatformViewsController
-  XCTAssertTrue([flutterPlatformViewsController submitFrame:std::move(mock_surface)
+         submitFrame:std::move(mock_surface)
-                                             withIosContext:nil
+      withIosContext:std::make_shared<flutter::IOSContextNoop>()
            grContext:nil]);
 
   XCTAssertTrue([flutterView.subviews indexOfObject:clippingView1] <
@@ -3945,9 +3951,9 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
         [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return true; },
         [](const flutter::SurfaceFrame& surface_frame) { return true; },
         /*frame_size=*/SkISize::Make(800, 600));
-
+    XCTAssertTrue([flutterPlatformViewsController
-    XCTAssertTrue([flutterPlatformViewsController submitFrame:std::move(mock_surface)
+           submitFrame:std::move(mock_surface)
-                                               withIosContext:nil
+        withIosContext:std::make_shared<flutter::IOSContextNoop>()
              grContext:nil]);
 
     // Disposing won't remove embedded views until the view is removed from the composition_order_
@@ -3975,9 +3981,9 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
         [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return true; },
         [](const flutter::SurfaceFrame& surface_frame) { return true; },
         /*frame_size=*/SkISize::Make(800, 600));
-
+    XCTAssertTrue([flutterPlatformViewsController
-    XCTAssertTrue([flutterPlatformViewsController submitFrame:std::move(mock_surface)
+           submitFrame:std::move(mock_surface)
-                                               withIosContext:nil
+        withIosContext:std::make_shared<flutter::IOSContextNoop>()
              grContext:nil]);
 
     // Disposing won't remove embedded views until the view is removed from the composition_order_
@@ -4051,9 +4057,8 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
       [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return true; },
       [](const flutter::SurfaceFrame& surface_frame) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
-
   [flutterPlatformViewsController submitFrame:std::move(mock_surface)
-                               withIosContext:nil
+                               withIosContext:std::make_shared<flutter::IOSContextNoop>()
                                     grContext:nil];
 
   UIView* someView = [[UIView alloc] init];
@@ -4130,9 +4135,8 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
       [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return true; },
       [](const flutter::SurfaceFrame& surface_frame) { return true; },
       /*frame_size=*/SkISize::Make(800, 600));
-
   [flutterPlatformViewsController submitFrame:std::move(mock_surface)
-                               withIosContext:nil
+                               withIosContext:std::make_shared<flutter::IOSContextNoop>()
                                     grContext:nil];
 
   XCTAssertEqual(flutterView.subviews.count, 1u);
@@ -4252,7 +4256,7 @@ fml::RefPtr<fml::TaskRunner> GetDefaultTaskRunner() {
   });
 
   [flutterPlatformViewsController submitFrame:std::move(mock_surface)
-                               withIosContext:nil
+                               withIosContext:std::make_shared<flutter::IOSContextNoop>()
                                     grContext:nil];
 
   XCTAssertTrue(submit_info.has_value());