Animated Dark Mode Switch for macOS 26

AnimatedDarkMode.m

#import <AppKit/AppKit.h>
#import <dispatch/dispatch.h>
#import <dlfcn.h>
#import <objc/message.h>

typedef bool (*SLSGetAppearanceThemeLegacyFunc)(void);
typedef void (*SLSSetAppearanceThemeNotifyingFunc)(BOOL, BOOL);
typedef id (*ObjCClassMessageSendFunc)(id, SEL);
typedef void (*ObjCPostChangeMessageSendFunc)(id, SEL, unsigned long long, void (^)(void));

static void ExitWithMessage(int code, NSString *message) {
    fprintf(stderr, "%s\n", message.UTF8String);
    exit(code);
}

static void *LoadSkyLight(void) {
    void *handle = dlopen(
        "/System/Library/PrivateFrameworks/SkyLight.framework/SkyLight",
        RTLD_LAZY | RTLD_LOCAL
    );

    if (!handle) {
        handle = dlopen(
            "/System/Library/PrivateFrameworks/SkyLight.framework/Versions/A/SkyLight",
            RTLD_LAZY | RTLD_LOCAL
        );
    }

    if (!handle) {
        ExitWithMessage(1, [NSString stringWithFormat:@"dlopen SkyLight failed: %s", dlerror()]);
    }

    return handle;
}

int main(int argc, const char *argv[]) {
    @autoreleasepool {
        void *skyLight = LoadSkyLight();
        SLSGetAppearanceThemeLegacyFunc getAppearance =
            (SLSGetAppearanceThemeLegacyFunc)dlsym(skyLight, "SLSGetAppearanceThemeLegacy");
        SLSSetAppearanceThemeNotifyingFunc setAppearance =
            (SLSSetAppearanceThemeNotifyingFunc)dlsym(skyLight, "SLSSetAppearanceThemeNotifying");

        if (!getAppearance || !setAppearance) {
            ExitWithMessage(1, @"Could not resolve SkyLight appearance functions.");
        }

        Class transitionClass = NSClassFromString(@"NSGlobalPreferenceTransition");
        SEL transitionSelector = NSSelectorFromString(@"transition");
        SEL postSelector = NSSelectorFromString(@"postChangeNotification:completionHandler:");

        if (![transitionClass respondsToSelector:transitionSelector]) {
            ExitWithMessage(1, @"NSGlobalPreferenceTransition +transition is unavailable.");
        }

        BOOL targetDarkMode = !getAppearance();
        setAppearance(targetDarkMode, false);

        id transition = ((ObjCClassMessageSendFunc)objc_msgSend)(transitionClass, transitionSelector);
        if (![transition respondsToSelector:postSelector]) {
            ExitWithMessage(
                1,
                @"NSGlobalPreferenceTransition -postChangeNotification:completionHandler: is unavailable."
            );
        }

        __block BOOL didExit = NO;
        void (^finish)(void) = ^{
            if (didExit) {
                return;
            }

            didExit = YES;
            exit(0);
        };

        ((ObjCPostChangeMessageSendFunc)objc_msgSend)(transition, postSelector, 0, finish);
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 3 * NSEC_PER_SEC), dispatch_get_main_queue(), finish);

        [[NSRunLoop mainRunLoop] run];
    }

    return 0;
}