refactor: match upstream macOS a11y handling (#47144)

shell/browser/mac/electron_application.mm

@@ -8,12 +8,14 @@
 #include <utility>
 
 #include "base/auto_reset.h"
+#include "base/mac/mac_util.h"
 #include "base/observer_list.h"
 #include "base/strings/sys_string_conversions.h"
 #include "content/public/browser/browser_accessibility_state.h"
 #include "content/public/browser/native_event_processor_mac.h"
 #include "content/public/browser/native_event_processor_observer_mac.h"
 #include "content/public/browser/scoped_accessibility_mode.h"
+#include "content/public/common/content_features.h"
 #include "shell/browser/browser.h"
 #include "shell/browser/mac/dict_util.h"
 #import "shell/browser/mac/electron_application_delegate.h"
@@ -31,12 +33,19 @@ inline void dispatch_sync_main(dispatch_block_t block) {
 }  // namespace
 
 @interface AtomApplication () <NativeEventProcessor> {
+  int _AXEnhancedUserInterfaceRequests;
+  BOOL _voiceOverEnabled;
+  BOOL _sonomaAccessibilityRefinementsAreActive;
   base::ObserverList<content::NativeEventProcessorObserver>::Unchecked
       observers_;
 }
+// Enables/disables screen reader support on changes to VoiceOver status.
+- (void)voiceOverStateChanged:(BOOL)voiceOverEnabled;
 @end
 
 @implementation AtomApplication {
+  std::unique_ptr<content::ScopedAccessibilityMode>
+      _scoped_accessibility_mode_voiceover;
   std::unique_ptr<content::ScopedAccessibilityMode>
       _scoped_accessibility_mode_general;
 }
@@ -45,6 +54,37 @@ inline void dispatch_sync_main(dispatch_block_t block) {
   return (AtomApplication*)[super sharedApplication];
 }
 
+- (void)finishLaunching {
+  [super finishLaunching];
+
+  _sonomaAccessibilityRefinementsAreActive =
+      base::mac::MacOSVersion() >= 14'00'00 &&
+      base::FeatureList::IsEnabled(
+          features::kSonomaAccessibilityActivationRefinements);
+}
+
+- (void)observeValueForKeyPath:(NSString*)keyPath
+                      ofObject:(id)object
+                        change:(NSDictionary*)change
+                       context:(void*)context {
+  if ([keyPath isEqualToString:@"voiceOverEnabled"] &&
+      context == content::BrowserAccessibilityState::GetInstance()) {
+    NSNumber* newValueNumber = [change objectForKey:NSKeyValueChangeNewKey];
+    DCHECK([newValueNumber isKindOfClass:[NSNumber class]]);
+
+    if ([newValueNumber isKindOfClass:[NSNumber class]]) {
+      [self voiceOverStateChanged:[newValueNumber boolValue]];
+    }
+
+    return;
+  }
+
+  [super observeValueForKeyPath:keyPath
+                       ofObject:object
+                         change:change
+                        context:context];
+}
+
 - (void)willPowerOff:(NSNotification*)notify {
   userStoppedShutdown_ = shouldShutdown_ && !shouldShutdown_.Run();
 }
@@ -214,14 +254,7 @@ inline void dispatch_sync_main(dispatch_block_t block) {
 - (void)accessibilitySetValue:(id)value forAttribute:(NSString*)attribute {
   bool is_manual_ax = [attribute isEqualToString:@"AXManualAccessibility"];
   if ([attribute isEqualToString:@"AXEnhancedUserInterface"] || is_manual_ax) {
-    if (![value boolValue]) {
-      _scoped_accessibility_mode_general.reset();
-    } else if (!_scoped_accessibility_mode_general) {
-      _scoped_accessibility_mode_general =
-          content::BrowserAccessibilityState::GetInstance()
-              ->CreateScopedModeForProcess(ui::kAXModeComplete);
-    }
-
+    [self enableScreenReaderCompleteModeAfterDelay:[value boolValue]];
     electron::Browser::Get()->OnAccessibilitySupportChanged();
 
     // Don't call the superclass function for AXManualAccessibility,
@@ -241,8 +274,11 @@ inline void dispatch_sync_main(dispatch_block_t block) {
   // recommends turning on a11y when an AT accesses the 'accessibilityRole'
   // property. This function is accessed frequently, so we only change the
   // accessibility state when accessibility is already disabled.
-  if (!_scoped_accessibility_mode_general) {
-    ui::AXMode target_mode = ui::kAXModeBasic;
+  if (!_scoped_accessibility_mode_general &&
+      !_scoped_accessibility_mode_voiceover) {
+    ui::AXMode target_mode = _sonomaAccessibilityRefinementsAreActive
+                                 ? ui::AXMode::kNativeAPIs
+                                 : ui::kAXModeBasic;
     _scoped_accessibility_mode_general =
         content::BrowserAccessibilityState::GetInstance()
             ->CreateScopedModeForProcess(target_mode |
@@ -252,6 +288,82 @@ inline void dispatch_sync_main(dispatch_block_t block) {
   return [super accessibilityRole];
 }
 
+- (void)enableScreenReaderCompleteMode:(BOOL)enable {
+  if (enable) {
+    if (!_scoped_accessibility_mode_voiceover) {
+      _scoped_accessibility_mode_voiceover =
+          content::BrowserAccessibilityState::GetInstance()
+              ->CreateScopedModeForProcess(ui::kAXModeComplete |
+                                           ui::AXMode::kFromPlatform |
+                                           ui::AXMode::kScreenReader);
+    }
+  } else {
+    _scoped_accessibility_mode_voiceover.reset();
+  }
+}
+
+// We need to call enableScreenReaderCompleteMode:YES from performSelector:...
+// but there's no way to supply a BOOL as a parameter, so we have this
+// explicit enable... helper method.
+- (void)enableScreenReaderCompleteMode {
+  _AXEnhancedUserInterfaceRequests = 0;
+  [self enableScreenReaderCompleteMode:YES];
+}
+
+- (void)voiceOverStateChanged:(BOOL)voiceOverEnabled {
+  _voiceOverEnabled = voiceOverEnabled;
+
+  [self enableScreenReaderCompleteMode:voiceOverEnabled];
+}
+
+// Enables or disables screen reader support for non-VoiceOver assistive
+// technology (AT), possibly after a delay.
+//
+// Now that we directly monitor VoiceOver status, we no longer watch for
+// changes to AXEnhancedUserInterface for that signal from VO. However, other
+// AT can set a value for AXEnhancedUserInterface, so we can't ignore it.
+// Unfortunately, as of macOS Sonoma, we sometimes see spurious changes to
+// AXEnhancedUserInterface (quick on and off). We debounce by waiting for these
+// changes to settle down before updating the screen reader state.
+- (void)enableScreenReaderCompleteModeAfterDelay:(BOOL)enable {
+  // If VoiceOver is already explicitly enabled, ignore requests from other AT.
+  if (_voiceOverEnabled) {
+    return;
+  }
+
+  // If this is a request to disable screen reader support, and we haven't seen
+  // a corresponding enable request, go ahead and disable.
+  if (!enable && _AXEnhancedUserInterfaceRequests == 0) {
+    [self enableScreenReaderCompleteMode:NO];
+    return;
+  }
+
+  // Use a counter to track requests for changes to the screen reader state.
+  if (enable) {
+    _AXEnhancedUserInterfaceRequests++;
+  } else {
+    _AXEnhancedUserInterfaceRequests--;
+  }
+
+  DCHECK_GE(_AXEnhancedUserInterfaceRequests, 0);
+
+  // _AXEnhancedUserInterfaceRequests > 0 means we want to enable screen
+  // reader support, but we'll delay that action until there are no more state
+  // change requests within a two-second window. Cancel any pending
+  // performSelector:..., and schedule a new one to restart the countdown.
+  [NSObject cancelPreviousPerformRequestsWithTarget:self
+                                           selector:@selector
+                                           (enableScreenReaderCompleteMode)
+                                             object:nil];
+
+  if (_AXEnhancedUserInterfaceRequests > 0) {
+    const float kTwoSecondDelay = 2.0;
+    [self performSelector:@selector(enableScreenReaderCompleteMode)
+               withObject:nil
+               afterDelay:kTwoSecondDelay];
+  }
+}
+
 - (void)orderFrontStandardAboutPanel:(id)sender {
   electron::Browser::Get()->ShowAboutPanel();
 }