Build iOS and macOS Obj-C with -fapplication-extension flag

common/config.gni

@@ -57,6 +57,7 @@ if (is_ios || is_mac) {
   flutter_cflags_objc = [
     "-Werror=overriding-method-mismatch",
     "-Werror=undeclared-selector",
+    "-fapplication-extension",
   ]
   flutter_cflags_objcc = flutter_cflags_objc
   flutter_cflags_objc_arc = flutter_cflags_objc + [ "-fobjc-arc" ]

shell/platform/darwin/ios/BUILD.gn

@@ -44,7 +44,10 @@ source_set("flutter_framework_source_arc") {
   cflags_objc = flutter_cflags_objc_arc
   cflags_objcc = flutter_cflags_objcc_arc
 
-  defines = [ "FLUTTER_FRAMEWORK=1" ]
+  defines = [
+    "FLUTTER_FRAMEWORK=1",
+    "APPLICATION_EXTENSION_API_ONLY=1",
+  ]
   allow_circular_includes_from = [ ":flutter_framework_source" ]
   deps = [
     ":flutter_framework_source",
@@ -153,7 +156,10 @@ source_set("flutter_framework_source") {
 
   sources += _flutter_framework_headers
 
-  defines = [ "FLUTTER_FRAMEWORK=1" ]
+  defines = [
+    "FLUTTER_FRAMEWORK=1",
+    "APPLICATION_EXTENSION_API_ONLY=1",
+  ]
 
   if (shell_enable_metal) {
     sources += [
@@ -320,7 +326,10 @@ shared_library("create_flutter_framework_dylib") {
 
   output_name = "Flutter"
 
-  ldflags = [ "-Wl,-install_name,@rpath/Flutter.framework/Flutter" ]
+  ldflags = [
+    "-Wl,-install_name,@rpath/Flutter.framework/Flutter",
+    "-fapplication-extension",
+  ]
 
   public = _flutter_framework_headers
 

shell/platform/darwin/ios/framework/Headers/FlutterAppDelegate.h

@@ -24,6 +24,7 @@
  * code as necessary from FlutterAppDelegate.mm.
  */
 FLUTTER_DARWIN_EXPORT
+NS_EXTENSION_UNAVAILABLE_IOS("Disallowed in app extensions")
 @interface FlutterAppDelegate
     : UIResponder <UIApplicationDelegate, FlutterPluginRegistry, FlutterAppLifeCycleProvider>
 

shell/platform/darwin/ios/framework/Headers/FlutterPlugin.h

@@ -353,7 +353,8 @@ typedef enum {
  *
  * @param delegate The receiving object, such as the plugin's main class.
  */
-- (void)addApplicationDelegate:(NSObject<FlutterPlugin>*)delegate;
+- (void)addApplicationDelegate:(NSObject<FlutterPlugin>*)delegate
+    NS_EXTENSION_UNAVAILABLE_IOS("Disallowed in plugins used in app extensions");
 
 /**
  * Returns the file name for the given asset.

shell/platform/darwin/ios/framework/Headers/FlutterPluginAppLifeCycleDelegate.h

@@ -13,6 +13,7 @@ NS_ASSUME_NONNULL_BEGIN
  * Propagates `UIAppDelegate` callbacks to registered plugins.
  */
 FLUTTER_DARWIN_EXPORT
+NS_EXTENSION_UNAVAILABLE_IOS("Disallowed in plugins used in app extensions")
 @interface FlutterPluginAppLifeCycleDelegate : NSObject <UNUserNotificationCenterDelegate>
 
 /**

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

@@ -849,7 +849,11 @@ - (BOOL)createShell:(NSString*)entrypoint
   );
 
   _isGpuDisabled =
+#if APPLICATION_EXTENSION_API_ONLY
+      NO;
+#else
       [UIApplication sharedApplication].applicationState == UIApplicationStateBackground;
+#endif
   // Create the shell. This is a blocking operation.
   std::unique_ptr<flutter::Shell> shell = flutter::Shell::Create(
       /*platform_data=*/platformData,
@@ -1433,7 +1437,7 @@ - (void)addMethodCallDelegate:(NSObject<FlutterPlugin>*)delegate
   }];
 }
 
-- (void)addApplicationDelegate:(NSObject<FlutterPlugin>*)delegate {
+- (void)addApplicationDelegate:(NSObject<FlutterPlugin>*)delegate NS_EXTENSION_UNAVAILABLE_IOS("") {
   id<UIApplicationDelegate> appDelegate = [[UIApplication sharedApplication] delegate];
   if ([appDelegate conformsToProtocol:@protocol(FlutterAppLifeCycleProvider)]) {
     id<FlutterAppLifeCycleProvider> lifeCycleProvider =

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

@@ -158,6 +158,7 @@ - (void)setSystemChromeApplicationSwitcherDescription:(NSDictionary*)object {
 }
 
 - (void)setSystemChromeEnabledSystemUIOverlays:(NSArray*)overlays {
+#if !APPLICATION_EXTENSION_API_ONLY
   // Checks if the top status bar should be visible. This platform ignores all
   // other overlays
 
@@ -175,9 +176,11 @@ - (void)setSystemChromeEnabledSystemUIOverlays:(NSArray*)overlays {
         postNotificationName:FlutterViewControllerHideHomeIndicator
                       object:nil];
   }
+#endif
 }
 
 - (void)setSystemChromeEnabledSystemUIMode:(NSString*)mode {
+#if !APPLICATION_EXTENSION_API_ONLY
   // Checks if the top status bar should be visible, reflected by edge to edge setting. This
   // platform ignores all other system ui modes.
 
@@ -195,6 +198,7 @@ - (void)setSystemChromeEnabledSystemUIMode:(NSString*)mode {
         postNotificationName:FlutterViewControllerHideHomeIndicator
                       object:nil];
   }
+#endif
 }
 
 - (void)restoreSystemChromeSystemUIOverlays {
@@ -231,9 +235,11 @@ - (void)setSystemChromeSystemUIOverlayStyle:(NSDictionary*)message {
                       object:nil
                     userInfo:@{@(kOverlayStyleUpdateNotificationKey) : @(statusBarStyle)}];
   } else {
+#if !APPLICATION_EXTENSION_API_ONLY
     // Note: -[UIApplication setStatusBarStyle] is deprecated in iOS9
     // in favor of delegating to the view controller
     [[UIApplication sharedApplication] setStatusBarStyle:statusBarStyle];
+#endif
   }
 }
 
@@ -249,11 +255,15 @@ - (void)popSystemNavigator:(BOOL)isAnimated {
   if (navigationController) {
     [navigationController popViewControllerAnimated:isAnimated];
   } else {
+#if !APPLICATION_EXTENSION_API_ONLY
     UIViewController* rootViewController =
         [UIApplication sharedApplication].keyWindow.rootViewController;
     if (engineViewController != rootViewController) {
+#endif
       [engineViewController dismissViewControllerAnimated:isAnimated completion:nil];
+#if !APPLICATION_EXTENSION_API_ONLY
     }
+#endif
   }
 }
 

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

@@ -814,9 +814,14 @@ - (void)viewDidAppear:(BOOL)animated {
   if ([_engine.get() viewController] == self) {
     [self onUserSettingsChanged:nil];
     [self onAccessibilityStatusChanged:nil];
+
+#if !APPLICATION_EXTENSION_API_ONLY
     if (UIApplication.sharedApplication.applicationState == UIApplicationStateActive) {
+#endif
       [[_engine.get() lifecycleChannel] sendMessage:@"AppLifecycleState.resumed"];
+#if !APPLICATION_EXTENSION_API_ONLY
     }
+#endif
   }
   [super viewDidAppear:animated];
 }
@@ -1304,8 +1309,13 @@ - (void)viewDidLayoutSubviews {
   // There is no guarantee that UIKit will layout subviews when the application is active. Creating
   // the surface when inactive will cause GPU accesses from the background. Only wait for the first
   // frame to render when the application is actually active.
-  bool applicationIsActive =
+  BOOL applicationIsActive =
+
+#if APPLICATION_EXTENSION_API_ONLY
+      YES;
+#else
       [UIApplication sharedApplication].applicationState == UIApplicationStateActive;
+#endif
 
   // This must run after updateViewportMetrics so that the surface creation tasks are queued after
   // the viewport metrics update tasks.
@@ -1804,6 +1814,7 @@ - (void)onOrientationPreferencesUpdated:(NSNotification*)notification {
 }
 
 - (void)performOrientationUpdate:(UIInterfaceOrientationMask)new_preferences {
+#if !APPLICATION_EXTENSION_API_ONLY
   if (new_preferences != _orientationPreferences) {
     _orientationPreferences = new_preferences;
 
@@ -1850,6 +1861,7 @@ - (void)performOrientationUpdate:(UIInterfaceOrientationMask)new_preferences {
       }
     }
   }
+#endif
 }
 
 - (void)onHideHomeIndicatorNotification:(NSNotification*)notification {
@@ -1951,7 +1963,12 @@ - (void)onUserSettingsChanged:(NSNotification*)notification {
 }
 
 - (CGFloat)textScaleFactor {
+#if APPLICATION_EXTENSION_API_ONLY
+  UIContentSizeCategory category =
+      self.mainScreenIfViewLoaded.traitCollection.preferredContentSizeCategory;
+#else
   UIContentSizeCategory category = [UIApplication sharedApplication].preferredContentSizeCategory;
+#endif
   // The delta is computed by approximating Apple's typography guidelines:
   // https://developer.apple.com/ios/human-interface-guidelines/visual-design/typography/
   //