fix: AXManualAccessibility showing failure

docs/tutorial/accessibility.md

@@ -28,6 +28,8 @@ On macOS, third-party assistive technology can toggle accessibility features ins
 Electron applications by setting the `AXManualAccessibility` attribute
 programmatically:
 
+Using Objective-C:
+
 ```objc
 CFStringRef kAXManualAccessibility = CFSTR("AXManualAccessibility");
 
@@ -43,5 +45,16 @@ CFStringRef kAXManualAccessibility = CFSTR("AXManualAccessibility");
 }
 ```
 
+Using Swift:
+
+```swift
+import Cocoa
+let name = CommandLine.arguments.count >= 2 ? CommandLine.arguments[1] : "Electron"
+let pid = NSWorkspace.shared.runningApplications.first(where: {$0.localizedName == name})!.processIdentifier
+let axApp = AXUIElementCreateApplication(pid)
+let result = AXUIElementSetAttributeValue(axApp, "AXManualAccessibility" as CFString, true as CFTypeRef)
+print("Setting 'AXManualAccessibility' \(error.rawValue == 0 ? "succeeded" : "failed")")
+```
+
 [a11y-docs]: https://www.chromium.org/developers/design-documents/accessibility#TOC-How-Chrome-detects-the-presence-of-Assistive-Technology
 [setAccessibilitySupportEnabled]: ../api/app.md#appsetaccessibilitysupportenabledenabled-macos-windows

shell/browser/mac/electron_application.mm

@@ -175,11 +175,13 @@ - (void)handleURLEvent:(NSAppleEventDescriptor*)event
   electron::Browser::Get()->OpenURL(base::SysNSStringToUTF8(url));
 }
 
+// AXEnhancedUserInterface is an undocumented attribute that screen reader
+// related functionality sets when running, and AXManualAccessibility is an
+// attribute Electron specifically allows third-party apps to use to enable
+// a11y features in Electron.
 - (void)accessibilitySetValue:(id)value forAttribute:(NSString*)attribute {
-  // Undocumented attribute that screen reader related functionality
-  // sets when running.
-  if ([attribute isEqualToString:@"AXEnhancedUserInterface"] ||
-      [attribute isEqualToString:@"AXManualAccessibility"]) {
+  bool is_manual_ax = [attribute isEqualToString:@"AXManualAccessibility"];
+  if ([attribute isEqualToString:@"AXEnhancedUserInterface"] || is_manual_ax) {
     auto* ax_state = content::BrowserAccessibilityState::GetInstance();
     if ([value boolValue]) {
       ax_state->OnScreenReaderDetected();
@@ -188,6 +190,12 @@ - (void)accessibilitySetValue:(id)value forAttribute:(NSString*)attribute {
     }
 
     electron::Browser::Get()->OnAccessibilitySupportChanged();
+
+    // Don't call the superclass function for AXManualAccessibility,
+    // as it will log an AXError and make it appear as though the attribute
+    // failed to take effect.
+    if (is_manual_ax)
+      return;
   }
 
   return [super accessibilitySetValue:value forAttribute:attribute];