[ios]make the screenIfViewLoaded and windowSceneIfLoaded helpers reusable (#44303)

The existing `screenIfViewLoaded` and `windowSceneIfLoaded` functions are private helpers of `FlutterViewController` class. This PR moves the logic to a category of the `UIViewController`, so it can be reused for any `UIViewController`s. 

*List which issues are fixed by this PR. You must list at least one issue.*

#43972 (comment)

*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*

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

Author: hellohuanlin

ci/licenses_golden/licenses_flutter

@@ -2672,6 +2672,9 @@ ORIGIN: ../../../flutter/shell/platform/darwin/ios/framework/Source/KeyCodeMap_I
 ORIGIN: ../../../flutter/shell/platform/darwin/ios/framework/Source/SemanticsObject.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/ios/framework/Source/SemanticsObject.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/ios/framework/Source/SemanticsObjectTest.mm + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/darwin/ios/framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/darwin/ios/framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.mm + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/darwin/ios/framework/Source/UIViewController_FlutterScreenAndSceneIfLoadedTest.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/ios/framework/Source/VsyncWaiterIosTest.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge.mm + ../../../flutter/LICENSE
@@ -5395,6 +5398,9 @@ FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/KeyCodeMap_Int
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/SemanticsObject.h
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/SemanticsObject.mm
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/SemanticsObjectTest.mm
+FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.h
+FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.mm
+FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/UIViewController_FlutterScreenAndSceneIfLoadedTest.mm
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/VsyncWaiterIosTest.mm
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge.h
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge.mm

shell/platform/darwin/ios/BUILD.gn

@@ -123,6 +123,8 @@ source_set("flutter_framework_source") {
     "framework/Source/KeyCodeMap_Internal.h",
     "framework/Source/SemanticsObject.h",
     "framework/Source/SemanticsObject.mm",
+    "framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.h",
+    "framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.mm",
     "framework/Source/accessibility_bridge.h",
     "framework/Source/accessibility_bridge.mm",
     "framework/Source/accessibility_text_entry.h",
@@ -298,6 +300,7 @@ shared_library("ios_test_flutter") {
     "framework/Source/FlutterUndoManagerPluginTest.mm",
     "framework/Source/FlutterViewControllerTest.mm",
     "framework/Source/SemanticsObjectTest.mm",
+    "framework/Source/UIViewController_FlutterScreenAndSceneIfLoadedTest.mm",
     "framework/Source/connection_collection_test.mm",
   ]
   deps = [

shell/platform/darwin/ios/framework/Source/FlutterEngine.mm

@@ -30,6 +30,7 @@
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterUndoManagerDelegate.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterUndoManagerPlugin.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterViewController_Internal.h"
+#import "flutter/shell/platform/darwin/ios/framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/connection_collection.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/platform_message_response_darwin.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/profiler_metrics_ios.h"
@@ -880,7 +881,7 @@ - (BOOL)createShell:(NSString*)entrypoint
 
 #if APPLICATION_EXTENSION_API_ONLY
   if (@available(iOS 13.0, *)) {
-    _isGpuDisabled = self.viewController.windowSceneIfViewLoaded.activationState ==
+    _isGpuDisabled = self.viewController.flutterWindowSceneIfViewLoaded.activationState ==
                      UISceneActivationStateBackground;
   } else {
     // [UIApplication sharedApplication API is not available for app extension.

shell/platform/darwin/ios/framework/Source/FlutterPlatformPlugin.mm

@@ -11,6 +11,7 @@
 
 #include "flutter/fml/logging.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterViewController_Internal.h"
+#import "flutter/shell/platform/darwin/ios/framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.h"
 
 namespace {
 
@@ -293,7 +294,7 @@ - (void)popSystemNavigator:(BOOL)isAnimated {
 #if APPLICATION_EXTENSION_API_ONLY
     if (@available(iOS 15.0, *)) {
       rootViewController =
-          [engineViewController windowSceneIfViewLoaded].keyWindow.rootViewController;
+          [engineViewController flutterWindowSceneIfViewLoaded].keyWindow.rootViewController;
     } else {
       FML_LOG(WARNING)
           << "rootViewController is not available in application extension prior to iOS 15.0.";

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -26,6 +26,7 @@
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterTextInputDelegate.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterView.h"
+#import "flutter/shell/platform/darwin/ios/framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/platform_message_response_darwin.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/vsync_waiter_ios.h"
 #import "flutter/shell/platform/darwin/ios/platform_view_ios.h"
@@ -516,25 +517,6 @@ - (void)loadView {
   return pointer_data;
 }
 
-- (UIWindowScene*)windowSceneIfViewLoaded {
-  if (self.viewIfLoaded == nil) {
-    FML_LOG(WARNING) << "Trying to access the window scene before the view is loaded.";
-    return nil;
-  }
-  return self.viewIfLoaded.window.windowScene;
-}
-
-- (UIScreen*)screenIfViewLoaded {
-  if (@available(iOS 13.0, *)) {
-    if (self.viewIfLoaded == nil) {
-      FML_LOG(WARNING) << "Trying to access the screen before the view is loaded.";
-      return nil;
-    }
-    return [self windowSceneIfViewLoaded].screen;
-  }
-  return UIScreen.mainScreen;
-}
-
 static void SendFakeTouchEvent(UIScreen* screen,
                                FlutterEngine* engine,
                                CGPoint location,
@@ -554,7 +536,7 @@ - (BOOL)scrollViewShouldScrollToTop:(UIScrollView*)scrollView {
     return NO;
   }
   CGPoint statusBarPoint = CGPointZero;
-  UIScreen* screen = [self screenIfViewLoaded];
+  UIScreen* screen = [self flutterScreenIfViewLoaded];
   if (screen) {
     SendFakeTouchEvent(screen, _engine.get(), statusBarPoint, flutter::PointerData::Change::kDown);
     SendFakeTouchEvent(screen, _engine.get(), statusBarPoint, flutter::PointerData::Change::kUp);
@@ -869,8 +851,8 @@ - (void)viewDidAppear:(BOOL)animated {
     BOOL stateIsActive = YES;
 #if APPLICATION_EXTENSION_API_ONLY
     if (@available(iOS 13.0, *)) {
-      stateIsActive =
-          self.windowSceneIfViewLoaded.activationState == UISceneActivationStateForegroundActive;
+      stateIsActive = self.flutterWindowSceneIfViewLoaded.activationState ==
+                      UISceneActivationStateForegroundActive;
     }
 #else
     stateIsActive = UIApplication.sharedApplication.applicationState == UIApplicationStateActive;
@@ -1166,7 +1148,7 @@ - (void)dispatchTouches:(NSSet*)touches
   // Activate or pause the correction of delivery frame rate of touch events.
   [self triggerTouchRateCorrectionIfNeeded:touches];
 
-  const CGFloat scale = [self screenIfViewLoaded].scale;
+  const CGFloat scale = [self flutterScreenIfViewLoaded].scale;
   auto packet =
       std::make_unique<flutter::PointerDataPacket>(touches.count + touches_to_remove_count);
 
@@ -1381,7 +1363,7 @@ - (void)updateViewportMetricsIfNeeded {
 
 - (void)viewDidLayoutSubviews {
   CGRect viewBounds = self.view.bounds;
-  CGFloat scale = [self screenIfViewLoaded].scale;
+  CGFloat scale = [self flutterScreenIfViewLoaded].scale;
 
   // Purposefully place this not visible.
   _scrollView.get().frame = CGRectMake(0.0, 0.0, viewBounds.size.width, 0.0);
@@ -1400,8 +1382,8 @@ - (void)viewDidLayoutSubviews {
   bool applicationOrSceneIsActive = YES;
 #if APPLICATION_EXTENSION_API_ONLY
   if (@available(iOS 13.0, *)) {
-    applicationOrSceneIsActive =
-        self.windowSceneIfViewLoaded.activationState == UISceneActivationStateForegroundActive;
+    applicationOrSceneIsActive = self.flutterWindowSceneIfViewLoaded.activationState ==
+                                 UISceneActivationStateForegroundActive;
   }
 #else
   applicationOrSceneIsActive =
@@ -1436,7 +1418,7 @@ - (void)viewSafeAreaInsetsDidChange {
 
 // Set _viewportMetrics physical size.
 - (void)setViewportMetricsSize {
-  UIScreen* screen = [self screenIfViewLoaded];
+  UIScreen* screen = [self flutterScreenIfViewLoaded];
   if (!screen) {
     return;
   }
@@ -1450,7 +1432,7 @@ - (void)setViewportMetricsSize {
 //
 // Viewport paddings represent the iOS safe area insets.
 - (void)setViewportMetricsPaddings {
-  UIScreen* screen = [self screenIfViewLoaded];
+  UIScreen* screen = [self flutterScreenIfViewLoaded];
   if (!screen) {
     return;
   }
@@ -1616,7 +1598,7 @@ - (FlutterKeyboardMode)calculateKeyboardAttachMode:(NSNotification*)notification
     return FlutterKeyboardModeHidden;
   }
 
-  CGRect screenRect = [self screenIfViewLoaded].bounds;
+  CGRect screenRect = [self flutterScreenIfViewLoaded].bounds;
   CGRect adjustedKeyboardFrame = keyboardFrame;
   adjustedKeyboardFrame.origin.y += [self calculateMultitaskingAdjustment:screenRect
                                                             keyboardFrame:keyboardFrame];
@@ -1656,7 +1638,7 @@ - (CGFloat)calculateMultitaskingAdjustment:(CGRect)screenRect keyboardFrame:(CGR
     }
     CGRect viewRectRelativeToScreen =
         [self.viewIfLoaded convertRect:self.viewIfLoaded.frame
-                     toCoordinateSpace:[self screenIfViewLoaded].coordinateSpace];
+                     toCoordinateSpace:[self flutterScreenIfViewLoaded].coordinateSpace];
     CGFloat viewBottom = CGRectGetMaxY(viewRectRelativeToScreen);
     CGFloat offset = screenHeight - viewBottom;
     if (offset > 0) {
@@ -1672,14 +1654,14 @@ - (CGFloat)calculateKeyboardInset:(CGRect)keyboardFrame keyboardMode:(NSInteger)
     // Calculate how much of the keyboard intersects with the view.
     CGRect viewRectRelativeToScreen =
         [self.viewIfLoaded convertRect:self.viewIfLoaded.frame
-                     toCoordinateSpace:[self screenIfViewLoaded].coordinateSpace];
+                     toCoordinateSpace:[self flutterScreenIfViewLoaded].coordinateSpace];
     CGRect intersection = CGRectIntersection(keyboardFrame, viewRectRelativeToScreen);
     CGFloat portionOfKeyboardInView = CGRectGetHeight(intersection);
 
     // The keyboard is treated as an inset since we want to effectively reduce the window size by
     // the keyboard height. The Dart side will compute a value accounting for the keyboard-consuming
     // bottom padding.
-    CGFloat scale = [self screenIfViewLoaded].scale;
+    CGFloat scale = [self flutterScreenIfViewLoaded].scale;
     return portionOfKeyboardInView * scale;
   }
   return 0;
@@ -1974,8 +1956,9 @@ - (void)performOrientationUpdate:(UIInterfaceOrientationMask)new_preferences {
     if (@available(iOS 16.0, *)) {
       NSSet<UIScene*>* scenes =
 #if APPLICATION_EXTENSION_API_ONLY
-          self.windowSceneIfViewLoaded ? [NSSet setWithObject:self.windowSceneIfViewLoaded]
-                                       : [NSSet set];
+          self.flutterWindowSceneIfViewLoaded
+              ? [NSSet setWithObject:self.flutterWindowSceneIfViewLoaded]
+              : [NSSet set];
 #else
           [UIApplication.sharedApplication.connectedScenes
               filteredSetUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(
@@ -1987,7 +1970,7 @@ - (void)performOrientationUpdate:(UIInterfaceOrientationMask)new_preferences {
     } else {
       UIInterfaceOrientationMask currentInterfaceOrientation;
       if (@available(iOS 13.0, *)) {
-        UIWindowScene* windowScene = [self windowSceneIfViewLoaded];
+        UIWindowScene* windowScene = [self flutterWindowSceneIfViewLoaded];
         if (!windowScene) {
           FML_LOG(WARNING)
               << "Accessing the interface orientation when the window scene is unavailable.";
@@ -2410,7 +2393,7 @@ - (BOOL)gestureRecognizer:(UIGestureRecognizer*)gestureRecognizer
 
 - (void)hoverEvent:(UIPanGestureRecognizer*)recognizer API_AVAILABLE(ios(13.4)) {
   CGPoint location = [recognizer locationInView:self.view];
-  CGFloat scale = [self screenIfViewLoaded].scale;
+  CGFloat scale = [self flutterScreenIfViewLoaded].scale;
   CGPoint oldLocation = _mouseState.location;
   _mouseState.location = {location.x * scale, location.y * scale};
 
@@ -2467,7 +2450,7 @@ - (void)hoverEvent:(UIPanGestureRecognizer*)recognizer API_AVAILABLE(ios(13.4))
 
 - (void)discreteScrollEvent:(UIPanGestureRecognizer*)recognizer API_AVAILABLE(ios(13.4)) {
   CGPoint translation = [recognizer translationInView:self.view];
-  const CGFloat scale = [self screenIfViewLoaded].scale;
+  const CGFloat scale = [self flutterScreenIfViewLoaded].scale;
 
   translation.x *= scale;
   translation.y *= scale;
@@ -2496,7 +2479,7 @@ - (void)discreteScrollEvent:(UIPanGestureRecognizer*)recognizer API_AVAILABLE(io
 
 - (void)continuousScrollEvent:(UIPanGestureRecognizer*)recognizer API_AVAILABLE(ios(13.4)) {
   CGPoint translation = [recognizer translationInView:self.view];
-  const CGFloat scale = [self screenIfViewLoaded].scale;
+  const CGFloat scale = [self flutterScreenIfViewLoaded].scale;
 
   flutter::PointerData pointer_data = [self generatePointerDataAtLastMouseLocation];
   pointer_data.device = reinterpret_cast<int64_t>(recognizer);

shell/platform/darwin/ios/framework/Source/FlutterViewControllerTest.mm

@@ -16,6 +16,7 @@
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterFakeKeyEvents.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterViewController_Internal.h"
+#import "flutter/shell/platform/darwin/ios/framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.h"
 #import "flutter/shell/platform/embedder/embedder.h"
 #import "flutter/third_party/spring_animation/spring_animation.h"
 
@@ -129,7 +130,6 @@ - (void)updateViewportMetricsIfNeeded;
 - (void)onUserSettingsChanged:(NSNotification*)notification;
 - (void)applicationWillTerminate:(NSNotification*)notification;
 - (void)goToApplicationLifecycle:(nonnull NSString*)state;
-- (UIScreen*)screenIfViewLoaded;
 - (void)handleKeyboardNotification:(NSNotification*)notification;
 - (CGFloat)calculateKeyboardInset:(CGRect)keyboardFrame keyboardMode:(int)keyboardMode;
 - (BOOL)shouldIgnoreKeyboardNotification:(NSNotification*)notification;
@@ -199,7 +199,7 @@ - (id)setUpMockView:(FlutterViewController*)viewControllerMock
              screen:(UIScreen*)screen
           viewFrame:(CGRect)viewFrame
      convertedFrame:(CGRect)convertedFrame {
-  OCMStub([viewControllerMock screenIfViewLoaded]).andReturn(screen);
+  OCMStub([viewControllerMock flutterScreenIfViewLoaded]).andReturn(screen);
   id mockView = OCMClassMock([UIView class]);
   OCMStub([mockView frame]).andReturn(viewFrame);
   OCMStub([mockView convertRect:viewFrame toCoordinateSpace:[OCMArg any]])
@@ -680,7 +680,7 @@ - (void)testCalculateKeyboardInset {
                                                                                  bundle:nil];
   FlutterViewController* viewControllerMock = OCMPartialMock(viewController);
   UIScreen* screen = [self setUpMockScreen];
-  OCMStub([viewControllerMock screenIfViewLoaded]).andReturn(screen);
+  OCMStub([viewControllerMock flutterScreenIfViewLoaded]).andReturn(screen);
 
   CGFloat screenWidth = screen.bounds.size.width;
   CGFloat screenHeight = screen.bounds.size.height;
@@ -943,7 +943,7 @@ - (void)testUpdateViewportMetricsIfNeeded_DoesNotInvokeEngineWhenShouldBeIgnored
                                                                                  bundle:nil];
   FlutterViewController* viewControllerMock = OCMPartialMock(viewController);
   UIScreen* screen = [self setUpMockScreen];
-  OCMStub([viewControllerMock screenIfViewLoaded]).andReturn(screen);
+  OCMStub([viewControllerMock flutterScreenIfViewLoaded]).andReturn(screen);
   mockEngine.viewController = viewController;
 
   id mockCoordinator = OCMProtocolMock(@protocol(UIViewControllerTransitionCoordinator));
@@ -965,7 +965,7 @@ - (void)testViewWillTransitionToSize_DoesDelayEngineCallIfNonZeroDuration {
                                                                                  bundle:nil];
   FlutterViewController* viewControllerMock = OCMPartialMock(viewController);
   UIScreen* screen = [self setUpMockScreen];
-  OCMStub([viewControllerMock screenIfViewLoaded]).andReturn(screen);
+  OCMStub([viewControllerMock flutterScreenIfViewLoaded]).andReturn(screen);
   mockEngine.viewController = viewController;
 
   // Mimic the device rotation with non-zero transition duration.
@@ -999,7 +999,7 @@ - (void)testViewWillTransitionToSize_DoesNotDelayEngineCallIfZeroDuration {
                                                                                  bundle:nil];
   FlutterViewController* viewControllerMock = OCMPartialMock(viewController);
   UIScreen* screen = [self setUpMockScreen];
-  OCMStub([viewControllerMock screenIfViewLoaded]).andReturn(screen);
+  OCMStub([viewControllerMock flutterScreenIfViewLoaded]).andReturn(screen);
   mockEngine.viewController = viewController;
 
   // Mimic the device rotation with zero transition duration.
@@ -1512,7 +1512,7 @@ - (void)orientationTestWithOrientationUpdate:(UIInterfaceOrientationMask)mask
     if (@available(iOS 16.0, *)) {
       mockWindowScene = OCMClassMock([UIWindowScene class]);
       mockVC = OCMPartialMock(realVC);
-      OCMStub([mockVC windowSceneIfViewLoaded]).andReturn(mockWindowScene);
+      OCMStub([mockVC flutterWindowSceneIfViewLoaded]).andReturn(mockWindowScene);
       if (realVC.supportedInterfaceOrientations == mask) {
         OCMReject([mockWindowScene requestGeometryUpdateWithPreferences:[OCMArg any]
                                                            errorHandler:[OCMArg any]]);
@@ -1540,7 +1540,7 @@ - (void)orientationTestWithOrientationUpdate:(UIInterfaceOrientationMask)mask
       if (@available(iOS 13.0, *)) {
         mockWindowScene = OCMClassMock([UIWindowScene class]);
         mockVC = OCMPartialMock(realVC);
-        OCMStub([mockVC windowSceneIfViewLoaded]).andReturn(mockWindowScene);
+        OCMStub([mockVC flutterWindowSceneIfViewLoaded]).andReturn(mockWindowScene);
         OCMStub(((UIWindowScene*)mockWindowScene).interfaceOrientation)
             .andReturn(currentOrientation);
       } else {

shell/platform/darwin/ios/framework/Source/FlutterViewController_Internal.h

@@ -65,7 +65,6 @@ typedef void (^FlutterKeyboardAnimationCallback)(fml::TimePoint);
 - (void)addInternalPlugins;
 - (void)deregisterNotifications;
 - (int32_t)accessibilityFlags;
-- (UIWindowScene*)windowSceneIfViewLoaded API_AVAILABLE(ios(13.0));
 
 @end
 

shell/platform/darwin/ios/framework/Source/UIViewController+FlutterScreenAndSceneIfLoaded.h

@@ -0,0 +1,21 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_UIVIEWCONTROLLER_FLUTTERSCREENANDSCENEIFLOADED_H_
+#define FLUTTER_UIVIEWCONTROLLER_FLUTTERSCREENANDSCENEIFLOADED_H_
+
+#import <UIKit/UIKit.h>
+
+@interface UIViewController (FlutterScreenAndSceneIfLoaded)
+
+/// Returns a UIWindowScene if the UIViewController's view is loaded, and nil otherwise.
+- (UIWindowScene*)flutterWindowSceneIfViewLoaded API_AVAILABLE(ios(13.0));
+
+/// Before iOS 13, returns the main screen; After iOS 13, returns the screen the UIViewController is
+/// attached to if its view is loaded, and nil otherwise.
+- (UIScreen*)flutterScreenIfViewLoaded;
+
+@end
+
+#endif  // FLUTTER_UIVIEWCONTROLLER_FLUTTERSCREENANDSCENEIFLOADED_H_