Get an array of running applications ordered by last use

CopyLaunchedApplicationsInFrontToBackOrder.c

#import <Carbon/Carbon.h>
#import <dlfcn.h>

/*
 * Returns an array of CFDictionaryRef types, each of which contains information about one of the processes.
 * The processes are ordered in front to back, i.e. in the same order they appear when typing command + tab, from left to right.
 * See the ProcessInformationCopyDictionary function documentation for the keys used in the dictionaries.
 * If something goes wrong, then this function returns NULL.
 */
CFArrayRef CopyLaunchedApplicationsInFrontToBackOrder(void)
{    
    CFArrayRef (*_LSCopyApplicationArrayInFrontToBackOrder)(uint32_t sessionID) = NULL;
    void       (*_LSASNExtractHighAndLowParts)(void const* asn, UInt32* psnHigh, UInt32* psnLow) = NULL;
    CFTypeID   (*_LSASNGetTypeID)(void) = NULL;
    
    void *lsHandle = dlopen("/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/LaunchServices", RTLD_LAZY);
    if (!lsHandle) { return NULL; }
    
    _LSCopyApplicationArrayInFrontToBackOrder = (CFArrayRef(*)(uint32_t))dlsym(lsHandle, "_LSCopyApplicationArrayInFrontToBackOrder");
    _LSASNExtractHighAndLowParts = (void(*)(void const*, UInt32*, UInt32*))dlsym(lsHandle, "_LSASNExtractHighAndLowParts");
    _LSASNGetTypeID = (CFTypeID(*)(void))dlsym(lsHandle, "_LSASNGetTypeID");
    
    if (_LSCopyApplicationArrayInFrontToBackOrder == NULL || _LSASNExtractHighAndLowParts == NULL || _LSASNGetTypeID == NULL) { return NULL; }
    
    CFMutableArrayRef orderedApplications = CFArrayCreateMutable(kCFAllocatorDefault, 64, &kCFTypeArrayCallBacks);
    if (!orderedApplications) { return NULL; }
    
    CFArrayRef apps = _LSCopyApplicationArrayInFrontToBackOrder(-1);
    if (!apps) { CFRelease(orderedApplications); return NULL; }
    
    CFIndex count = CFArrayGetCount(apps);
    for (CFIndex i = 0; i < count; i++)
    {
        ProcessSerialNumber psn = {0, kNoProcess};
        CFTypeRef asn = CFArrayGetValueAtIndex(apps, i);
        if (CFGetTypeID(asn) == _LSASNGetTypeID())
        {
            _LSASNExtractHighAndLowParts(asn, &psn.highLongOfPSN, &psn.lowLongOfPSN);
            
            CFDictionaryRef processInfo = ProcessInformationCopyDictionary(&psn, kProcessDictionaryIncludeAllInformationMask);
            if (processInfo)
            {
                CFArrayAppendValue(orderedApplications, processInfo);
                CFRelease(processInfo);
            }
        }
    }
    CFRelease(apps);
    
    CFArrayRef result = CFArrayGetCount(orderedApplications) == 0 ? NULL : CFArrayCreateCopy(kCFAllocatorDefault, orderedApplications);
    CFRelease(orderedApplications);
    return result;
}