Fix Appearance module to observe application appearance (facebook#1340)

This fixes the `Appearance.getColorScheme()` API to return the application-level appearance instead of the last appearance of any root view, which breaks down in multi-window applications. In Messenger Desktop we always respect the OS appearance for main and setting windows, but force a darkTheme in the calling UI. W/o this change returning from the calling UI would result in a wrong appearance setting on light theme OS setting Co-authored-by: Scott Kyle <skyle@fb.com>
ryanlntn · Aug 10, 2022 · c3e847a · c3e847a
1 parent 24acd40
commit c3e847a
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Showing 2 changed files with 21 additions and 14 deletions.
diff --git a/React/Base/RCTRootView.m b/React/Base/RCTRootView.m
@@ -431,15 +431,6 @@ - (void)traitCollectionDidChange:(UITraitCollection *)previousTraitCollection
                     RCTUserInterfaceStyleDidChangeNotificationTraitCollectionKey : self.traitCollection,
                   }];
 }
-#else // [TODO(macOS GH#774)
-- (void)viewDidChangeEffectiveAppearance {
-  [[NSNotificationCenter defaultCenter] postNotificationName:RCTUserInterfaceStyleDidChangeNotification
-                                                      object:self
-                                                    userInfo:@{
-                                                      RCTUserInterfaceStyleDidChangeNotificationTraitCollectionKey: self.effectiveAppearance,
-                                                    }];
-
-}
 #endif // ]TODO(macOS GH#774)
 
 

diff --git a/React/CoreModules/RCTAppearance.mm b/React/CoreModules/RCTAppearance.mm
@@ -137,21 +137,26 @@ - (instancetype)init
   return _currentColorScheme;
 }
 
+#if !TARGET_OS_OSX // TODO(macOS GH#774)
 - (void)appearanceChanged:(NSNotification *)notification
 {
   NSDictionary *userInfo = [notification userInfo];
-#if !TARGET_OS_OSX // TODO(macOS GH#774)
   UITraitCollection *traitCollection = nil;
   if (userInfo) {
     traitCollection = userInfo[RCTUserInterfaceStyleDidChangeNotificationTraitCollectionKey];
   }
   NSString *newColorScheme = RCTColorSchemePreference(traitCollection);
 #else // [TODO(macOS GH#774)
-  NSAppearance *appearance = nil;
-  if (userInfo) {
-    appearance = userInfo[RCTUserInterfaceStyleDidChangeNotificationTraitCollectionKey];
+- (void)observeValueForKeyPath:(NSString *)keyPath
+                      ofObject:(id)object
+                        change:(NSDictionary *)change
+                       context:(void *)context
+{
+  if (object != NSApp || ![keyPath isEqualToString:@"effectiveAppearance"]) {
+    [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
+    return;
   }
-  NSString *newColorScheme = RCTColorSchemePreference(appearance);
+  NSString *newColorScheme = RCTColorSchemePreference(nil);
 #endif // ]TODO(macOS GH#774)
   if (![_currentColorScheme isEqualToString:newColorScheme]) {
     _currentColorScheme = newColorScheme;
@@ -168,19 +173,30 @@ - (void)appearanceChanged:(NSNotification *)notification
 
 - (void)startObserving
 {
+#if !TARGET_OS_OSX // [TODO(macOS GH#774)
   if (@available(iOS 13.0, *)) {
     [[NSNotificationCenter defaultCenter] addObserver:self
                                              selector:@selector(appearanceChanged:)
                                                  name:RCTUserInterfaceStyleDidChangeNotification
                                                object:nil];
   }
+#else  
+  [NSApp addObserver:self
+          forKeyPath:@"effectiveAppearance"
+             options:NSKeyValueObservingOptionNew
+             context:nil];  
+#endif // ]TODO(macOS GH#774)
 }
 
 - (void)stopObserving
 {
+#if !TARGET_OS_OSX // [TODO(macOS GH#774)
   if (@available(iOS 13.0, *)) {
     [[NSNotificationCenter defaultCenter] removeObserver:self];
   }
+#else  
+  [NSApp removeObserver:self forKeyPath:@"effectiveAppearance" context:nil];  
+#endif // ]TODO(macOS GH#774)
 }
 
 @end