CGDisplayIOServicePort is deprecated in OS X >= 10.9, how to replace? - objective-c

Question

I did small app to allow quickly change screen resolutions on multiple monitors. I want to show product name as title of the monitor, and it's very simple to find using this code:
NSDictionary *deviceInfo = (__bridge NSDictionary *)IODisplayCreateInfoDictionary(CGDisplayIOServicePort(dispID), kIODisplayOnlyPreferredName);
NSDictionary *localizedNames = [deviceInfo objectForKey:[NSString stringWithUTF8String:kDisplayProductName]];
if([localizedNames count] > 0) {
_title = [localizedNames objectForKey:[[localizedNames allKeys] objectAtIndex:0]];
} else {
_title = #"Unknown display";
}
But CGDisplayIOServicePort is deprecated in OS X >= 10.9 and Apple's documentation says there is no replacement. How to find service port or product name without using this method?
I tried to iterate through IO-registry and tried to use IOServiceGetMatchingServices method to find display services but I'm not very familiar with IO-registry so I couldn't find solution.
Thanks for help!

Answer 1

It looks like #Eun's post missed a piece of information to close this discussion. With a little search, I found that IOServicePortFromCGDisplayID is not an API which Apple provides. Rather, it's a piece of open source code found here:
https://github.com/glfw/glfw/blob/e0a6772e5e4c672179fc69a90bcda3369792ed1f/src/cocoa_monitor.m
I copied IOServicePortFromCGDisplayID and also 'getDisplayName' from it.
I needed two tweaks to make it work on OS X 10.10.
Remove the code to handle serial number in IOServicePortFromCGDisplayID. (CFDictionaryGetValue for
kDisplaySerialNumber returns NULL for me.)
Remove project specific
error handling code in getDisplayName.
If you need more information
Issue tracker of the problem: github.com/glfw/glfw/issues/165
Commit
for the solution:
github.com/glfw/glfw/commit/e0a6772e5e4c672179fc69a90bcda3369792ed1f
I would thank Matthew Henry who submitted the code there.

Answer 2

Here is my take on the issue. I also started with the code from GLFW 3.1, file cocoa_monitor.m.
But I had to modify it in different ways than Hiroshi said, so here goes:
// Get the name of the specified display
- (NSString*) screenNameForDisplay: (NSNumber*) screen_id
{
CGDirectDisplayID displayID = [screen_id unsignedIntValue];
io_service_t serv = [self IOServicePortFromCGDisplayID: displayID];
if (serv == 0)
return #"unknown";
CFDictionaryRef info = IODisplayCreateInfoDictionary(serv, kIODisplayOnlyPreferredName);
IOObjectRelease(serv);
CFStringRef display_name;
CFDictionaryRef names = CFDictionaryGetValue(info, CFSTR(kDisplayProductName));
if ( !names ||
!CFDictionaryGetValueIfPresent(names, CFSTR("en_US"), (const void**) & display_name) )
{
// This may happen if a desktop Mac is running headless
CFRelease( info );
return #"unknown";
}
NSString * displayname = [NSString stringWithString: (__bridge NSString *) display_name];
CFRelease(info);
return displayname;
}
// Returns the io_service_t (an int) corresponding to a CG display ID, or 0 on failure.
// The io_service_t should be released with IOObjectRelease when not needed.
- (io_service_t) IOServicePortFromCGDisplayID: (CGDirectDisplayID) displayID
{
io_iterator_t iter;
io_service_t serv, servicePort = 0;
CFMutableDictionaryRef matching = IOServiceMatching("IODisplayConnect");
// releases matching for us
kern_return_t err = IOServiceGetMatchingServices( kIOMasterPortDefault, matching, & iter );
if ( err )
return 0;
while ( (serv = IOIteratorNext(iter)) != 0 )
{
CFDictionaryRef displayInfo;
CFNumberRef vendorIDRef;
CFNumberRef productIDRef;
CFNumberRef serialNumberRef;
displayInfo = IODisplayCreateInfoDictionary( serv, kIODisplayOnlyPreferredName );
Boolean success;
success = CFDictionaryGetValueIfPresent( displayInfo, CFSTR(kDisplayVendorID), (const void**) & vendorIDRef );
success &= CFDictionaryGetValueIfPresent( displayInfo, CFSTR(kDisplayProductID), (const void**) & productIDRef );
if ( !success )
{
CFRelease(displayInfo);
continue;
}
SInt32 vendorID;
CFNumberGetValue( vendorIDRef, kCFNumberSInt32Type, &vendorID );
SInt32 productID;
CFNumberGetValue( productIDRef, kCFNumberSInt32Type, &productID );
// If a serial number is found, use it.
// Otherwise serial number will be nil (= 0) which will match with the output of 'CGDisplaySerialNumber'
SInt32 serialNumber = 0;
if ( CFDictionaryGetValueIfPresent(displayInfo, CFSTR(kDisplaySerialNumber), (const void**) & serialNumberRef) )
{
CFNumberGetValue( serialNumberRef, kCFNumberSInt32Type, &serialNumber );
}
// If the vendor and product id along with the serial don't match
// then we are not looking at the correct monitor.
// NOTE: The serial number is important in cases where two monitors
// are the exact same.
if( CGDisplayVendorNumber(displayID) != vendorID ||
CGDisplayModelNumber(displayID) != productID ||
CGDisplaySerialNumber(displayID) != serialNumber )
{
CFRelease(displayInfo);
continue;
}
servicePort = serv;
CFRelease(displayInfo);
break;
}
IOObjectRelease(iter);
return servicePort;
}
This works fine for me in a screensaver I wrote under macOS 10.11 (El Capitan).
I tested it with the built-in display of my MacBookPro and an Apple Display connected via Thunderbolt.

Answer 3

As of macOS 10.15 -[NSScreen localizedName] is available:
NSLog(#"Name of main display is %#", NSScreen.mainScreen.localizedName);

Answer 4

NSString* screenNameForDisplay(CGDirectDisplayID displayID)
{
NSString *screenName = nil;
io_service_t service = IOServicePortFromCGDisplayID(displayID);
if (service)
{
NSDictionary *deviceInfo = (NSDictionary *)IODisplayCreateInfoDictionary(service, 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];
}