Fix glfwSetSystemThemeCallback and its Cocoa implementation

src/cocoa_init.m

@@ -175,6 +175,50 @@ static void createMenuBar(void)
     [NSApp performSelector:setAppleMenuSelector withObject:appMenu];
 }
 
+void nsAppearanceToGLFWTheme(NSAppearance* appearance, GLFWtheme* theme)
+{
+    NSAppearanceName name = appearance.name;
+    
+    if (name == NSAppearanceNameAqua)
+    {
+        theme->baseTheme = GLFW_BASE_THEME_LIGHT;
+    }
+    else if (name == NSAppearanceNameDarkAqua)
+    {
+        theme->baseTheme = GLFW_BASE_THEME_DARK;
+    }
+    else if (name == NSAppearanceNameVibrantLight)
+    {
+        theme->baseTheme = GLFW_BASE_THEME_LIGHT;
+        theme->flags |= GLFW_THEME_FLAG_VIBRANT;
+    }
+    else if (name == NSAppearanceNameVibrantDark)
+    {
+        theme->baseTheme = GLFW_BASE_THEME_DARK;
+        theme->flags |= GLFW_THEME_FLAG_VIBRANT;
+    }
+    if (name == NSAppearanceNameAccessibilityHighContrastAqua)
+    {
+        theme->baseTheme = GLFW_BASE_THEME_LIGHT;
+        theme->flags |= GLFW_THEME_FLAG_HIGH_CONTRAST;
+    }
+    else if (name == NSAppearanceNameAccessibilityHighContrastDarkAqua)
+    {
+        theme->baseTheme = GLFW_BASE_THEME_DARK;
+        theme->flags |= GLFW_THEME_FLAG_HIGH_CONTRAST;
+    }
+    else if (name == NSAppearanceNameAccessibilityHighContrastVibrantLight)
+    {
+        theme->baseTheme = GLFW_BASE_THEME_LIGHT;
+        theme->flags |= GLFW_THEME_FLAG_VIBRANT | GLFW_THEME_FLAG_HIGH_CONTRAST;
+    }
+    else if (name == NSAppearanceNameAccessibilityHighContrastVibrantDark)
+    {
+        theme->baseTheme = GLFW_BASE_THEME_DARK;
+        theme->flags |= GLFW_THEME_FLAG_VIBRANT | GLFW_THEME_FLAG_HIGH_CONTRAST;
+    }
+}
+
 // Create key code translation tables
 //
 static void createKeyTables(void)
@@ -393,6 +437,41 @@ static GLFWbool initializeTIS(void)
 - (void)doNothing:(id)object
 {
 }
+/*
+- (void)themeChanged:(NSNotification*)notification
+{
+    _glfwInputSystemTheme(NULL);
+}
+
+- (void)accentColorChanged
+{
+    _glfwInputSystemTheme(NULL);
+}*/
+
+- (void)observeValueForKeyPath:(NSString *)keyPath
+                      ofObject:(id)object
+                        change:(NSDictionary *)change
+                       context:(void *)context
+{
+    // This class is never subclassed, so it's safe to ignore the context parameter
+    
+    GLFWtheme theme = { 0, 0 };
+    nsAppearanceToGLFWTheme(NSApp.effectiveAppearance, &theme);
+    
+    NSColor* color = [[NSColor controlAccentColor] colorUsingColorSpace:NSColorSpace.genericRGBColorSpace];
+    
+    theme.flags |= GLFW_THEME_FLAG_HAS_COLOR;
+    theme.color[0] = color.redComponent * 255;
+    theme.color[1] = color.greenComponent * 255;
+    theme.color[2] = color.blueComponent * 255;
+    theme.color[3] = color.alphaComponent * 255;
+    
+    _glfwInputSystemTheme(&theme);
+    
+    /*if ([keyPath isEqualToString:@"controlAccentColor"]) {
+        [self accentColorChanged];
+    }*/
+}
 
 @end // GLFWHelper
 
@@ -641,6 +720,24 @@ int _glfwInitCocoa(void)
         return GLFW_FALSE;
 
     _glfwPollMonitorsCocoa();
+        
+    /*
+    [[NSNotificationCenter defaultCenter]
+        addObserver:_glfw.ns.helper
+           selector:@selector(themeChanged:)
+               name:@"AppleInterfaceThemeChangedNotification"
+             object:nil];
+    
+    [NSColor addObserver:_glfw.ns.helper
+              forKeyPath:@"controlAccentColor"
+                 options:0
+                 context:nil];
+    */
+    
+    [NSApp addObserver:_glfw.ns.helper
+            forKeyPath:@"effectiveAppearance"
+               options:0
+               context:nil];
 
     if (![[NSRunningApplication currentApplication] isFinishedLaunching])
         [NSApp run];

src/cocoa_platform.h

@@ -39,8 +39,10 @@
 #import <Cocoa/Cocoa.h>
 #else
 typedef void* id;
+typedef void NSAppearance;
 #endif
 
+
 // NOTE: Many Cocoa enum values have been renamed and we need to build across
 //       SDK versions where one is unavailable or deprecated.
 //       We use the newer names in code and replace them with the older names if
@@ -291,6 +293,8 @@ void _glfwRestoreVideoModeCocoa(_GLFWmonitor* monitor);
 
 float _glfwTransformYCocoa(float y);
 
+void nsAppearanceToGLFWTheme(NSAppearance* appearance, GLFWtheme* theme);
+
 void* _glfwLoadLocalVulkanLoaderCocoa(void);
 
 GLFWbool _glfwInitNSGL(void);

src/cocoa_window.m

@@ -1930,58 +1930,16 @@ void _glfwSetThemeCocoa(_GLFWwindow* window, GLFWtheme* theme)
 
 GLFWtheme* _glfwGetThemeCocoa(_GLFWwindow* window)
 {
-    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED, NULL); // TODO: remove
-    
-    // TODO: must use KVO to observe NSApplication NSAppearance for theme callback.
-    
     GLFWtheme* theme = &window->theme;
-    NSAppearanceName name = [window->ns.object appearance].name;
     
     theme->baseTheme = 0;
     theme->flags = 0;
     
-    if (name == NSAppearanceNameAqua)
-    {
-        theme->baseTheme = GLFW_BASE_THEME_LIGHT;
-    }
-    else if (name == NSAppearanceNameDarkAqua)
-    {
-        theme->baseTheme = GLFW_BASE_THEME_DARK;
-    }
-    else if (name == NSAppearanceNameVibrantLight)
-    {
-        theme->baseTheme = GLFW_BASE_THEME_LIGHT;
-        theme->flags |= GLFW_THEME_FLAG_VIBRANT;
-    }
-    else if (name == NSAppearanceNameVibrantDark)
-    {
-        theme->baseTheme = GLFW_BASE_THEME_DARK;
-        theme->flags |= GLFW_THEME_FLAG_VIBRANT;
-    }
-    if (name == NSAppearanceNameAccessibilityHighContrastAqua)
-    {
-        theme->baseTheme = GLFW_BASE_THEME_LIGHT;
-        theme->flags |= GLFW_THEME_FLAG_HIGH_CONTRAST;
-    }
-    else if (name == NSAppearanceNameAccessibilityHighContrastDarkAqua)
-    {
-        theme->baseTheme = GLFW_BASE_THEME_DARK;
-        theme->flags |= GLFW_THEME_FLAG_HIGH_CONTRAST;
-    }
-    else if (name == NSAppearanceNameAccessibilityHighContrastVibrantLight)
-    {
-        theme->baseTheme = GLFW_BASE_THEME_LIGHT;
-        theme->flags |= GLFW_THEME_FLAG_VIBRANT | GLFW_THEME_FLAG_HIGH_CONTRAST;
-    }
-    else if (name == NSAppearanceNameAccessibilityHighContrastVibrantDark)
-    {
-        theme->baseTheme = GLFW_BASE_THEME_DARK;
-        theme->flags |= GLFW_THEME_FLAG_VIBRANT | GLFW_THEME_FLAG_HIGH_CONTRAST;
-    }
+    nsAppearanceToGLFWTheme([window->ns.object appearance], theme);
     
     // TODO: this is not settable. Is there any reason in overriding a similar value? Does it apply to menu item highlights? If yes, then it must be overridden.
-    // TODO: must use KVO to observe the controlAccentColor for the theme callback.
     NSColor* color = [[NSColor controlAccentColor] colorUsingColorSpace:NSColorSpace.genericRGBColorSpace];
+    // TODO: Cannot use the accent color directly, for window themes, because the accent color is never overridden.
     
     theme->flags |= GLFW_THEME_FLAG_HAS_COLOR;
     theme->color[0] = color.redComponent * 255;

src/init.c

@@ -554,8 +554,9 @@ GLFWAPI GLFWthemefun glfwSetSystemThemeCallback(GLFWthemefun callback)
     
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
     
-    //return _glfw.platform.setSystemThemeCallback(callback);
-    
-    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED, NULL);
-    return NULL; // TODO: implement
+    //return _glfw.platform.setSystemThemeCallback(callback
+
+    _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
+    _GLFW_SWAP(GLFWthemefun, _glfw.callbacks.theme, callback);
+    return callback;
 }

src/input.c

@@ -477,6 +477,13 @@ void _glfwInputJoystickHat(_GLFWjoystick* js, int hat, char value)
     js->hats[hat] = value;
 }
 
+void _glfwInputSystemTheme(GLFWtheme* theme)
+{
+    assert(theme != NULL);
+    
+    if (_glfw.callbacks.theme)
+        _glfw.callbacks.theme(theme);
+}
 
 //////////////////////////////////////////////////////////////////////////
 //////                       GLFW internal API                      //////

src/internal.h

@@ -868,6 +868,7 @@ struct _GLFWlibrary
     struct {
         GLFWmonitorfun  monitor;
         GLFWjoystickfun joystick;
+        GLFWthemefun    theme;
     } callbacks;
 
     // These are defined in platform.h
@@ -934,6 +935,8 @@ void _glfwInputJoystickAxis(_GLFWjoystick* js, int axis, float value);
 void _glfwInputJoystickButton(_GLFWjoystick* js, int button, char value);
 void _glfwInputJoystickHat(_GLFWjoystick* js, int hat, char value);
 
+void _glfwInputSystemTheme(GLFWtheme* theme);
+
 void _glfwInputMonitor(_GLFWmonitor* monitor, int action, int placement);
 void _glfwInputMonitorWindow(_GLFWmonitor* monitor, _GLFWwindow* window);