How to Get the Display Name with the Display ID in Mac OS X?

Question

Hello! I was wondering if you could help me figure out how to progmatically get the Display Name for a monitor by using its Display ID number in Mac OS X (10.5)? A requirement is if I give a function the Display ID, it'll provide the Display Name in return (or vice versa).

Display Name looks something like this: "Color LCD", "SAMSUNG"

Display ID looks something like this: "69671872", "893830283"

NSScreen in Cocoa (Obj-C), or CGGetActiveDisplayList in Quartz (C), allow you to get the Display ID number for a monitor. Neither appear to have a method to get the Display Name. Oh no! Here's the code for NSScreen to get the Display ID:

NSArray *screenArray = [NSScreen screens];
NSDictionary *screenDescription = [[screenArray objectAtIndex:0] deviceDescription];
NSLog(@"Device ID: %@", [screenDescription objectForKey:@"NSScreenNumber"]);

System Profiler, and Displays under System Preferences, reference displays by Display Name, not Display ID.

I'm asking as I want to run an AppleScript, and it requires a Display Name rather than a Display ID. Any help is MUCH appreciated! :)

Answer 1

This gives you the localized display name:

static void KeyArrayCallback(const void* key, const void* value, void* context) { CFArrayAppendValue(context, key);  }

- (NSString*)localizedDisplayProductName
{
    NSDictionary* screenDictionary = [[NSScreen mainScreen] deviceDescription];
    NSNumber* screenID = [screenDictionary objectForKey:@"NSScreenNumber"];
    CGDirectDisplayID aID = [screenID unsignedIntValue];   
    CFStringRef localName = NULL;
    io_connect_t displayPort = CGDisplayIOServicePort(aID);
    CFDictionaryRef dict = (CFDictionaryRef)IODisplayCreateInfoDictionary(displayPort, 0);
    CFDictionaryRef names = CFDictionaryGetValue(dict, CFSTR(kDisplayProductName));
    if(names)
    {
     CFArrayRef langKeys = CFArrayCreateMutable(kCFAllocatorDefault, 0, &kCFTypeArrayCallBacks );
     CFDictionaryApplyFunction(names, KeyArrayCallback, (void*)langKeys);
     CFArrayRef orderLangKeys = CFBundleCopyPreferredLocalizationsFromArray(langKeys);
     CFRelease(langKeys);
     if(orderLangKeys && CFArrayGetCount(orderLangKeys))
     {
      CFStringRef langKey = CFArrayGetValueAtIndex(orderLangKeys, 0);
      localName = CFDictionaryGetValue(names, langKey);
      CFRetain(localName);
     }
     CFRelease(orderLangKeys);
    }
    CFRelease(dict);
    return [(NSString*)localName autorelease];
}

Answer 2

Or if you don't want to mess with the preferred localization array, pass the kIODisplayOnlyPreferredName flag to IODisplayCreateInfoDictionary()

Here is a less CoreFoundation, more Cocoa and somewhat reduced code that will do the same thing:

NSString* screenNameForDisplay(CGDirectDisplayID displayID)
{
    NSString *screenName = nil;

    NSDictionary *deviceInfo = (NSDictionary *)IODisplayCreateInfoDictionary(CGDisplayIOServicePort(displayID), kIODisplayOnlyPreferredName);
    NSDictionary *localizedNames = [deviceInfo objectForKey:[NSString stringWithUTF8String:kDisplayProductName]];

    if ([localizedNames count] > 0) {
     screenName = [[localizedNames objectForKey:[[localizedNames allKeys] objectAtIndex:0]] retain];
    }

    [deviceInfo release];
    return [screenName autorelease];
}