Add support for playing alert sound on MacOS (#19970)

flutter/flutter#62143

Author: tvolkert

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

@@ -146,7 +146,7 @@ - (void)dispatchKeyEvent:(NSEvent*)event ofType:(NSString*)type;
 - (void)sendInitialSettings;
 
 /**
- * Responsds to updates in the user settings and passes this data to the engine.
+ * Responds to updates in the user settings and passes this data to the engine.
  */
 - (void)onSettingsChanged:(NSNotification*)notification;
 
@@ -155,6 +155,12 @@ - (void)onSettingsChanged:(NSNotification*)notification;
  */
 - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result;
 
+/**
+ * Plays a system sound. |soundType| specifies which system sound to play. Valid
+ * values can be found in the SystemSoundType enum in the services SDK package.
+ */
+- (void)playSystemSound:(NSString*)soundType;
+
 /**
  * Reads the data from the clipboard. |format| specifies the media type of the
  * data to obtain.
@@ -490,6 +496,9 @@ - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
   if ([call.method isEqualToString:@"SystemNavigator.pop"]) {
     [NSApp terminate:self];
     result(nil);
+  } else if ([call.method isEqualToString:@"SystemSound.play"]) {
+    [self playSystemSound:call.arguments];
+    result(nil);
   } else if ([call.method isEqualToString:@"Clipboard.getData"]) {
     result([self getClipboardData:call.arguments]);
   } else if ([call.method isEqualToString:@"Clipboard.setData"]) {
@@ -500,6 +509,12 @@ - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
   }
 }
 
+- (void)playSystemSound:(NSString*)soundType {
+  if ([soundType isEqualToString:@"SystemSoundType.alert"]) {
+    NSBeep();
+  }
+}
+
 - (NSDictionary*)getClipboardData:(NSString*)format {
   NSPasteboard* pasteboard = [NSPasteboard generalPasteboard];
   if ([format isEqualToString:@(kTextPlainFormat)]) {