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

Question

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

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:

#import <Foundation/Foundation.h>
#import <IOKit/graphics/IOGraphicsLib.h>

NSString* _Nullable ScreenNameForDisplay(CGDirectDisplayID displayID)
{
    NSString *screenName = nil;
    
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
    NSDictionary *deviceInfo = CFBridgingRelease(IODisplayCreateInfoDictionary(CGDisplayIOServicePort(displayID), kIODisplayOnlyPreferredName));
#pragma clang diagnostic pop
    
    NSDictionary *localizedNames = deviceInfo[@(kDisplayProductName)];
    
    if (localizedNames.count > 0) {
        return localizedNames[localizedNames.allKeys[0]];
    }
    
    return nil;
}

int main(int argc, char *argv[])
{
    @autoreleasepool
    {
        NSLog(@"Main Display: %@", ScreenNameForDisplay(CGMainDisplayID()));
    }
}

Note: the CoreGraphics framework must be linked (-framework CoreGraphics)

Answer 2

Other answers use CGDisplayIOServicePort which was deprecated.

As of macOS 10.15 -[NSScreen localizedName] is available:

NSLog(@"Name of main display is %@", NSScreen.mainScreen.localizedName);

For the display ID you can still use -[NSScreen deviceDescription]:

NSLog(@"The ID of the main display is %@", NSScreen.mainScreen.deviceDescription[@"NSScreenNumber"]);

Answer 3

Categories rulez =)

NSArray *screens = [NSScreen screens];

for (NSScreen *screen in screens) {
    NSLog([NSString stringWithFormat:@"%@", [screen displayID]]);
    NSLog([NSString stringWithFormat:@"%@", [screen displayName]]);
}  

NSScreen+DisplayInfo.h

#import <Cocoa/Cocoa.h>

@interface NSScreen (DisplayInfo)

-(NSString*) displayName;
-(NSNumber*) displayID;

@end

NSScreen+DisplayInfo.m

#import "NSScreen+DisplayInfo.h"   
#import <IOKit/graphics/IOGraphicsLib.h>

@implementation NSScreen (DisplayInfo)

-(NSString*) displayName
{
    CGDirectDisplayID displayID = [[self displayID] intValue];

    NSString *screenName = nil;

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

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

    return screenName;
}

-(NSNumber*) displayID
{
    return [[self deviceDescription] valueForKey:@"NSScreenNumber"];
}
@end

Answer 4

I created an example project on github.com using the implementation of Robert Harder.
@robert-harder Thank you for providing the idea!

Answer 5

And here's a whole app that puts it together (http://cl.ly/40Hw):

/* 
 DisplayID.m
 Author: Robert Harder, rob@iHarder.net
 with help from http://stackoverflow.com/questions/1236498/how-to-get-the-display-name-with-the-display-id-in-mac-os-x

 Returns a list of display names and display IDs.
 Add the flag -v for more information on the screens.

 Compile from the command line:
   cc DisplayID.m -o DisplayID \
     -framework AppKit -framework Foundation -framework IOKit \
     -arch x86_64 -arch i386 -arch ppc7400

 Examples:

   $ DisplayID
   Color LCD : 69675202

   $ DisplayID -v
   Color LCD : 69675202
   {
       NSDeviceBitsPerSample = 8;
       NSDeviceColorSpaceName = NSCalibratedRGBColorSpace;
       NSDeviceIsScreen = YES;
       NSDeviceResolution = "NSSize: {72, 72}";
       NSDeviceSize = "NSSize: {1440, 900}";
       NSScreenNumber = 69675202;
   }
 */

#import <Foundation/Foundation.h>
#import <AppKit/AppKit.h>
#import <IOKit/graphics/IOGraphicsLib.h>

#define str_eq(s1,s2)  (!strcmp ((s1),(s2)))

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];
}


int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    BOOL verbose = NO;
    BOOL extraVerbose = NO;

    if( argc >= 2 ){
        if( str_eq( "-v",argv[1]) ){
            verbose = YES;
        } else if( str_eq( "-vv", argv[1] ) ){
            verbose = YES;
            extraVerbose = YES;
        } else {
            printf("USAGE: %s [-v[v]]\n", argv[0]);
            printf("Prints a list of names and numeric IDs for attached displays.\n");
            printf("  -v    Verbose mode. Prints more information about each display.\n");
            printf("  -vv   Extra verbose. Prints even more information.\n");
            return argc;
        }
    }

    NSArray *screenArray = [NSScreen screens];
    for( NSScreen *screen in screenArray ){

        NSDictionary *screenDescription = [screen deviceDescription];

        NSNumber *displayID = [screenDescription objectForKey:@"NSScreenNumber"];
        NSString *displayName =screenNameForDisplay([displayID intValue]);


        printf( "%s : %d\n", [displayName UTF8String], [displayID intValue]);       
        if( verbose ){
            printf( "%s\n", [[screenDescription description] UTF8String] );         
        }
        if( extraVerbose ){ 
            NSDictionary *deviceInfo = (NSDictionary *)IODisplayCreateInfoDictionary(CGDisplayIOServicePort([displayID intValue]), kIODisplayOnlyPreferredName);
            printf( "%s\n", [[deviceInfo description] UTF8String] );
        }

    }   // end for:


    [pool drain];
    return 0;
}

Answer 6

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];
}