iOS: A11y only disable during app resigning to background when voice over on (#32820)

Author: Chris Yang

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

@@ -179,6 +179,14 @@ FLUTTER_DARWIN_EXPORT
  */
 - (id<FlutterPluginRegistry>)pluginRegistry;
 
+/**
+ * A wrapper around UIAccessibilityIsVoiceOverRunning().
+ *
+ * As a C function, UIAccessibilityIsVoiceOverRunning() cannot be mocked in testing. Mock
+ * this class method to testing features depends on UIAccessibilityIsVoiceOverRunning().
+ */
++ (BOOL)isUIAccessibilityIsVoiceOverRunning;
+
 /**
  * True if at least one frame has rendered and the ViewController has appeared.
  *

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

@@ -826,7 +826,9 @@ - (void)applicationBecameActive:(NSNotification*)notification {
 
 - (void)applicationWillResignActive:(NSNotification*)notification {
   TRACE_EVENT0("flutter", "applicationWillResignActive");
-  self.view.accessibilityElementsHidden = YES;
+  if ([FlutterViewController isUIAccessibilityIsVoiceOverRunning]) {
+    self.view.accessibilityElementsHidden = YES;
+  }
   [self goToApplicationLifecycle:@"AppLifecycleState.inactive"];
 }
 
@@ -1718,6 +1720,10 @@ - (NSString*)lookupKeyForAsset:(NSString*)asset fromPackage:(NSString*)package {
   return _engine;
 }
 
++ (BOOL)isUIAccessibilityIsVoiceOverRunning {
+  return UIAccessibilityIsVoiceOverRunning();
+}
+
 #pragma mark - FlutterPluginRegistry
 
 - (NSObject<FlutterPluginRegistrar>*)registrarForPlugin:(NSString*)pluginKey {

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

@@ -939,6 +939,9 @@ - (void)testHideA11yElements {
   FlutterViewController* realVC = [[FlutterViewController alloc] initWithEngine:engine
                                                                         nibName:nil
                                                                          bundle:nil];
+  id flutterViewControllerClassMOCK = OCMClassMock([FlutterViewController class]);
+  [[[flutterViewControllerClassMOCK stub] andReturnValue:@YES] isUIAccessibilityIsVoiceOverRunning];
+
   XCTAssertFalse(realVC.view.accessibilityElementsHidden);
   [[NSNotificationCenter defaultCenter]
       postNotificationName:UIApplicationWillResignActiveNotification
@@ -949,6 +952,32 @@ - (void)testHideA11yElements {
                     object:nil];
   XCTAssertFalse(realVC.view.accessibilityElementsHidden);
   engine.viewController = nil;
+
+  [flutterViewControllerClassMOCK stopMocking];
+}
+
+- (void)testDontHideA11yElementsWhenVoiceOverIsOff {
+  FlutterDartProject* project = [[FlutterDartProject alloc] init];
+  FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"foobar" project:project];
+  [engine createShell:@"" libraryURI:@"" initialRoute:nil];
+  FlutterViewController* realVC = [[FlutterViewController alloc] initWithEngine:engine
+                                                                        nibName:nil
+                                                                         bundle:nil];
+  id flutterViewControllerClassMOCK = OCMClassMock([FlutterViewController class]);
+  [[[flutterViewControllerClassMOCK stub] andReturnValue:@NO] isUIAccessibilityIsVoiceOverRunning];
+
+  XCTAssertFalse(realVC.view.accessibilityElementsHidden);
+  [[NSNotificationCenter defaultCenter]
+      postNotificationName:UIApplicationWillResignActiveNotification
+                    object:nil];
+  XCTAssertFalse(realVC.view.accessibilityElementsHidden);
+  [[NSNotificationCenter defaultCenter]
+      postNotificationName:UIApplicationDidBecomeActiveNotification
+                    object:nil];
+  XCTAssertFalse(realVC.view.accessibilityElementsHidden);
+  engine.viewController = nil;
+
+  [flutterViewControllerClassMOCK stopMocking];
 }
 
 - (void)testNotifyLowMemory {