NSRunningApplication category to dynamically show and hide any running application icon in the Dock

NSRunningApplication+DockIcon.h

//
//  Created by Cédric Luthi on 2011-05-03
//  Copyright 2011-2012 Cédric Luthi. All rights reserved.
//

#import <AppKit/AppKit.h>

@interface NSRunningApplication (DockIcon)

- (BOOL) setDockIconHidden_xcd:(BOOL)dockIconHidden;

@end

NSRunningApplication+DockIcon.m

//
//  Created by Cédric Luthi on 2011-05-03
//  Copyright 2011-2012 Cédric Luthi. All rights reserved.
//

#import "NSRunningApplication+DockIcon.h"
#import <dlfcn.h>

@interface NSRunningApplication (Private)
- (CFTypeRef) applicationSerialNumber;
@end

@implementation NSRunningApplication (DockIcon)

static NSString *const HideDockIconKey = @"HideDockIcon";

static OSStatus (*_LSSetApplicationInformationItem)(int, CFTypeRef asn, CFStringRef key, CFStringRef value, CFDictionaryRef *info) = NULL;
static CFStringRef _kLSApplicationTypeKey = NULL;
static CFStringRef _kLSApplicationForegroundTypeKey = NULL;
static CFStringRef _kLSApplicationUIElementTypeKey = NULL;
static CFStringRef _kLSApplicationBackgroundOnlyTypeKey = NULL;

static BOOL isSafe = NO;

+ (void) load
{
	NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
	[self performSelector:@selector(initializeDockIcon) withObject:nil afterDelay:0.0];
	[pool drain];
}

static CFStringRef launchServicesKey(const char *symbol)
{
	CFStringRef *keyPtr = dlsym(RTLD_DEFAULT, symbol);
	return keyPtr ? *keyPtr : NULL;
}

+ (void) initializeDockIcon
{
	if (![[NSUserDefaults standardUserDefaults] boolForKey:HideDockIconKey])
		[[NSRunningApplication currentApplication] setDockIconHidden_xcd:NO];
	
	_LSSetApplicationInformationItem = dlsym(RTLD_DEFAULT, "_LSSetApplicationInformationItem");
	_kLSApplicationTypeKey = launchServicesKey("_kLSApplicationTypeKey");
	_kLSApplicationForegroundTypeKey = launchServicesKey("_kLSApplicationForegroundTypeKey");
	_kLSApplicationUIElementTypeKey = launchServicesKey("_kLSApplicationUIElementTypeKey");
	_kLSApplicationBackgroundOnlyTypeKey = launchServicesKey("_kLSApplicationBackgroundOnlyTypeKey");
	
	BOOL allSymbolsFound = _LSSetApplicationInformationItem && _kLSApplicationTypeKey &&
	                       _kLSApplicationForegroundTypeKey && _kLSApplicationUIElementTypeKey && _kLSApplicationBackgroundOnlyTypeKey;
	if (!allSymbolsFound)
		return;
	
	NSMethodSignature *asnMethodSignature = [NSRunningApplication instanceMethodSignatureForSelector:@selector(applicationSerialNumber)];
	NSString *asnMethodReturnType = asnMethodSignature ? [NSString stringWithUTF8String:[asnMethodSignature methodReturnType]] : @"";
	
	isSafe = [asnMethodReturnType isEqualToString:@"^{__LSASN=}"];
}

- (BOOL) setDockIconHidden_xcd:(BOOL)dockIconHidden
{
	BOOL isCurrentApplication = [self isEqual:[NSRunningApplication currentApplication]];
	if (isCurrentApplication)
		[[NSUserDefaults standardUserDefaults] setBool:dockIconHidden forKey:HideDockIconKey];
	
	OSStatus status = noErr;
	if (dockIconHidden)
	{
		if (!isSafe)
			return NO;
		
		BOOL isBackgroundOnlyType = self.bundleURL ? [[[NSBundle bundleWithURL:self.bundleURL] objectForInfoDictionaryKey:@"LSBackgroundOnly"] boolValue] : YES;
		CFStringRef applicationType = isBackgroundOnlyType ? _kLSApplicationBackgroundOnlyTypeKey : _kLSApplicationUIElementTypeKey;
		status = _LSSetApplicationInformationItem(-2, [self applicationSerialNumber], _kLSApplicationTypeKey, applicationType, NULL);
	}
	else
	{
		if (isCurrentApplication)
		{
			ProcessSerialNumber psn;
			status = GetProcessForPID(self.processIdentifier, &psn);
			if (status != noErr)
				return NO;
			
			status = TransformProcessType(&psn, kProcessTransformToForegroundApplication);
		}
		else
		{
			if (!isSafe)
				return NO;
			
			status = _LSSetApplicationInformationItem(-2, [self applicationSerialNumber], _kLSApplicationTypeKey, _kLSApplicationForegroundTypeKey, NULL);
		}
	}
	
	return status == noErr;
}

@end