如何在OS X中检测屏幕是否关闭？

#import <IOKit/IOKitLib.h>

BOOL isScreenClosed() {
    io_service_t service = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceNameMatching("IODisplayWrangler"));
    if (service) {
        CFDictionaryRef displayInfo = IODisplayCreateInfoDictionary(service, kIODisplayOnlyPreferredName);
        if (displayInfo) {
            CFBooleanRef isAsleep = CFDictionaryGetValue(displayInfo, CFSTR(kIODisplayIsAsleepKey));
            if (isAsleep != NULL && CFBooleanGetValue(isAsleep)) {
                CFRelease(displayInfo);
                IOObjectRelease(service);
                return YES;
            }
            CFRelease(displayInfo);
        }
        IOObjectRelease(service);
    }
    return NO;
}