Build iOS with -fapplication-extension flag

common/config.gni

@@ -22,6 +22,9 @@ declare_args() {
 
   # Whether to include backtrace support.
   enable_backtrace = true
+
+  # Whether to include --fapplication-extension when build iOS framework.
+  darwin_extension_safe = false
 }
 
 # feature_defines_list ---------------------------------------------------------
@@ -61,10 +64,9 @@ if (is_ios || is_mac) {
     "-Werror=overriding-method-mismatch",
     "-Werror=undeclared-selector",
   ]
-  if (is_mac) {
+  if (darwin_extension_safe || is_mac) {
     flutter_cflags_objc += [ "-fapplication-extension" ]
   }
-
   flutter_cflags_objcc = flutter_cflags_objc
   flutter_cflags_objc_arc = flutter_cflags_objc + [ "-fobjc-arc" ]
   flutter_cflags_objcc_arc = flutter_cflags_objc_arc

shell/platform/darwin/ios/BUILD.gn

@@ -13,6 +13,7 @@ import("//flutter/shell/platform/darwin/common/framework_shared.gni")
 import("//flutter/testing/testing.gni")
 
 _flutter_framework_dir = "$root_out_dir/Flutter.framework"
+_flutter_xcframework_dir = "$root_out_dir/Flutter.xcframework"
 
 shell_gpu_configuration("ios_gpu_configuration") {
   enable_software = true
@@ -44,6 +45,9 @@ source_set("flutter_framework_source_arc") {
   cflags_objcc = flutter_cflags_objcc_arc
 
   defines = [ "FLUTTER_FRAMEWORK=1" ]
+  if (darwin_extension_safe) {
+    defines += [ "APPLICATION_EXTENSION_API_ONLY=1" ]
+  }
   allow_circular_includes_from = [ ":flutter_framework_source" ]
   deps = [
     ":flutter_framework_source",
@@ -153,6 +157,9 @@ source_set("flutter_framework_source") {
   sources += _flutter_framework_headers
 
   defines = [ "FLUTTER_FRAMEWORK=1" ]
+  if (darwin_extension_safe) {
+    defines += [ "APPLICATION_EXTENSION_API_ONLY=1" ]
+  }
 
   if (shell_enable_metal) {
     sources += [
@@ -321,6 +328,10 @@ shared_library("create_flutter_framework_dylib") {
 
   ldflags = [ "-Wl,-install_name,@rpath/Flutter.framework/Flutter" ]
 
+  if (darwin_extension_safe) {
+    ldflags += [ "-fapplication-extension" ]
+  }
+
   public = _flutter_framework_headers
 
   deps = [
@@ -411,10 +422,24 @@ copy("copy_license") {
 shared_library("copy_and_verify_framework_module") {
   framework_search_path = rebase_path("$root_out_dir")
   visibility = [ ":*" ]
-  cflags_objc = [ "-F$framework_search_path" ]
+  cflags_objc = [
+    "-F$framework_search_path",
+    "-fapplication-extension",
+  ]
+
+  if (darwin_extension_safe) {
+    ldflags = [
+      "-F$framework_search_path",
+      "-fapplication-extension",
+      "-Xlinker",
+      "-fatal_warnings",
+    ]
+    frameworks = [ "Flutter.framework" ]
+    deps = [ ":copy_dylib" ]
+  }
 
   sources = [ "framework/Source/FlutterUmbrellaImport.m" ]
-  deps = [
+  deps += [
     ":copy_framework_headers",
     ":copy_framework_info_plist",
     ":copy_framework_module_map",
@@ -439,7 +464,7 @@ group("universal_flutter_framework") {
 
 action("flutter_framework") {
   script = "//flutter/sky/tools/create_xcframework.py"
-  outputs = [ "$root_out_dir/Flutter.xcframework" ]
+  outputs = [ "$_flutter_xcframework_dir" ]
   args = [
     "--frameworks",
     rebase_path("$_flutter_framework_dir"),

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/FlutterDartProject.mm

@@ -32,6 +32,39 @@
 
 static const char* kApplicationKernelSnapshotFileName = "kernel_blob.bin";
 
+NS_INLINE NSBundle* FLTFrameworkBundle() {
+  NSBundle* mainBundle = [NSBundle mainBundle];
+  NSBundle* bundle = FLTFrameworkBundleWithIdentifier([FlutterDartProject defaultBundleIdentifier]);
+
+  // App extension bundle is in Runner.app/PlugIns/Extension.appex.
+  if ([mainBundle.bundleURL.pathExtension isEqualToString:@"appex"]) {
+    // Up two levels.
+    NSBundle* appBundle =
+        [NSBundle bundleWithURL:mainBundle.bundleURL.URLByDeletingLastPathComponent
+                                    .URLByDeletingLastPathComponent];
+    bundle = FLTFrameworkBundleInternal([FlutterDartProject defaultBundleIdentifier],
+                                        appBundle.privateFrameworksURL);
+  }
+
+  if (bundle == nil) {
+    bundle = mainBundle;
+  }
+
+  return bundle;
+}
+
+NS_INLINE NSURL* FLTAssetsFromBundle(NSBundle* bundle) {
+  NSString* assetsPathFromInfoPlist = [bundle objectForInfoDictionaryKey:@"FLTAssetsPath"];
+  NSString* flutterAssetsName =
+      assetsPathFromInfoPlist != nil ? assetsPathFromInfoPlist : @"flutter_assets";
+  NSURL* assets = [bundle URLForResource:flutterAssetsName withExtension:nil];
+
+  if ([assets checkResourceIsReachableAndReturnError:NULL]) {
+    return assets;
+  }
+  return nil;
+}
+
 flutter::Settings FLTDefaultSettingsForBundle(NSBundle* bundle, NSProcessInfo* processInfoOrNil) {
   auto command_line = flutter::CommandLineFromNSProcessInfo(processInfoOrNil);
 
@@ -46,10 +79,7 @@
 
   bool hasExplicitBundle = bundle != nil;
   if (bundle == nil) {
-    bundle = FLTFrameworkBundleWithIdentifier([FlutterDartProject defaultBundleIdentifier]);
-  }
-  if (bundle == nil) {
-    bundle = mainBundle;
+    bundle = FLTFrameworkBundle();
   }
 
   auto settings = flutter::SettingsFromCommandLine(command_line);
@@ -122,29 +152,24 @@
 
   // Checks to see if the flutter assets directory is already present.
   if (settings.assets_path.empty()) {
-    NSString* assetsName = [FlutterDartProject flutterAssetsName:bundle];
-    NSString* assetsPath = [bundle pathForResource:assetsName ofType:@""];
+    NSURL* assetsURL = FLTAssetsFromBundle(bundle);
 
-    if (assetsPath.length == 0) {
-      assetsPath = [mainBundle pathForResource:assetsName ofType:@""];
-    }
-
-    if (assetsPath.length == 0) {
-      NSLog(@"Failed to find assets path for \"%@\"", assetsName);
+    if (assetsURL == nil) {
+      NSLog(@"Failed to find assets path for \"%@\"", bundle);
     } else {
-      settings.assets_path = assetsPath.UTF8String;
+      settings.assets_path = assetsURL.path.UTF8String;
 
       // Check if there is an application kernel snapshot in the assets directory we could
       // potentially use.  Looking for the snapshot makes sense only if we have a VM that can use
       // it.
       if (!flutter::DartVM::IsRunningPrecompiledCode()) {
         NSURL* applicationKernelSnapshotURL =
-            [NSURL URLWithString:@(kApplicationKernelSnapshotFileName)
-                   relativeToURL:[NSURL fileURLWithPath:assetsPath]];
-        if ([[NSFileManager defaultManager] fileExistsAtPath:applicationKernelSnapshotURL.path]) {
+            [assetsURL URLByAppendingPathComponent:@(kApplicationKernelSnapshotFileName)];
+        NSError* error;
+        if ([applicationKernelSnapshotURL checkResourceIsReachableAndReturnError:&error]) {
           settings.application_kernel_asset = applicationKernelSnapshotURL.path.UTF8String;
         } else {
-          NSLog(@"Failed to find snapshot: %@", applicationKernelSnapshotURL.path);
+          NSLog(@"Failed to find snapshot at %@: %@", applicationKernelSnapshotURL.path, error);
         }
       }
     }
@@ -331,11 +356,9 @@ - (instancetype)initWithSettings:(const flutter::Settings&)settings {
 
 + (NSString*)flutterAssetsName:(NSBundle*)bundle {
   if (bundle == nil) {
-    bundle = FLTFrameworkBundleWithIdentifier([FlutterDartProject defaultBundleIdentifier]);
-  }
-  if (bundle == nil) {
-    bundle = [NSBundle mainBundle];
+    bundle = FLTFrameworkBundle();
   }
+
   NSString* flutterAssetsName = [bundle objectForInfoDictionaryKey:@"FLTAssetsPath"];
   if (flutterAssetsName == nil) {
     flutterAssetsName = @"Frameworks/App.framework/flutter_assets";

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

@@ -850,7 +850,11 @@ - (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,
@@ -1452,7 +1456,7 @@ - (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

@@ -813,9 +813,14 @@ - (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];
 }
@@ -1287,8 +1292,13 @@ - (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.
@@ -1808,6 +1818,10 @@ - (void)performOrientationUpdate:(UIInterfaceOrientationMask)new_preferences {
     _orientationPreferences = new_preferences;
 
     if (@available(iOS 16.0, *)) {
+#if APPLICATION_EXTENSION_API_ONLY
+      UIWindowScene* windowScene = self.viewIfLoaded.window.windowScene;
+      [self performOrientationUpdateOnWindowScene:windowScene];
+#else
       for (UIScene* scene in UIApplication.sharedApplication.connectedScenes) {
         if (![scene isKindOfClass:[UIWindowScene class]]) {
           continue;
@@ -1825,7 +1839,9 @@ - (void)performOrientationUpdate:(UIInterfaceOrientationMask)new_preferences {
                                     }];
         [self setNeedsUpdateOfSupportedInterfaceOrientations];
       }
+#endif
     } else {
+#if !APPLICATION_EXTENSION_API_ONLY
       UIInterfaceOrientationMask currentInterfaceOrientation =
           1 << [[UIApplication sharedApplication] statusBarOrientation];
       if (!(_orientationPreferences & currentInterfaceOrientation)) {
@@ -1848,10 +1864,28 @@ - (void)performOrientationUpdate:(UIInterfaceOrientationMask)new_preferences {
                                       forKey:@"orientation"];
         }
       }
+#endif
     }
   }
 }
 
+- (void)performOrientationUpdateOnWindowScene:(UIWindowScene*)windowScene API_AVAILABLE(ios(16.0)) {
+  if (windowScene == nil) {
+    return;
+  }
+
+  UIWindowSceneGeometryPreferencesIOS* preference = [[UIWindowSceneGeometryPreferencesIOS alloc]
+      initWithInterfaceOrientations:_orientationPreferences];
+  [windowScene
+      requestGeometryUpdateWithPreferences:preference
+                              errorHandler:^(NSError* error) {
+                                os_log_error(OS_LOG_DEFAULT,
+                                             "Failed to change device orientation: %@", error);
+                              }];
+  [self setNeedsUpdateOfSupportedInterfaceOrientations];
+  [preference release];
+}
+
 - (void)onHideHomeIndicatorNotification:(NSNotification*)notification {
   self.isHomeIndicatorHidden = YES;
 }
@@ -1951,7 +1985,12 @@ - (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/
   //