Bug 1945302 - Support "Prefer non-blinking cursor" setting on macOS. r=mac-reviewers,mstange

Safari and Chrome both supports this a11y setting.

Differential Revision: https://phabricator.services.mozilla.com/D236451

Author: emilio

widget/cocoa/moz.build

@@ -165,6 +165,7 @@ RESOURCE_FILES.__setattr__(
 )
 
 OS_LIBS += [
+    "-framework Accessibility",
     "-framework IOSurface",
     "-framework Vision",
 ]

widget/cocoa/nsLookAndFeel.mm

@@ -23,6 +23,7 @@
 
 #import <Cocoa/Cocoa.h>
 #import <Carbon/Carbon.h>
+#import <Accessibility/Accessibility.h>
 #import <AppKit/NSColor.h>
 
 // This must be included last:
@@ -386,6 +387,13 @@ static bool SystemWantsDarkTheme() {
   return [aquaOrDarkAqua isEqualToString:NSAppearanceNameDarkAqua];
 }
 
+static bool PrefersNonBlinkingTextInsertionIndicator() {
+  if (@available(macOS 15.0, *)) {
+    return AXPrefersNonBlinkingTextInsertionIndicator();
+  }
+  return false;
+}
+
 nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
   NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
 
@@ -400,7 +408,7 @@ static bool SystemWantsDarkTheme() {
       aResult = 3;
       break;
     case IntID::CaretBlinkTime:
-      aResult = 567;
+      aResult = PrefersNonBlinkingTextInsertionIndicator() ? -1 : 567;
       break;
     case IntID::CaretWidth:
       aResult = 1;
@@ -609,6 +617,15 @@ + (void)startObserving {
 - (instancetype)init {
   self = [super init];
 
+  if (@available(macOS 15.0, *)) {
+    [NSNotificationCenter.defaultCenter
+        addObserver:self
+           selector:@selector(cachedValuesChanged)
+               name:
+                   AXPrefersNonBlinkingTextInsertionIndicatorDidChangeNotification
+             object:nil];
+  }
+
   [NSNotificationCenter.defaultCenter
       addObserver:self
          selector:@selector(colorsChanged)