touchbar IOHID watcher

HID.c

// compile and run from the commandline with:
//    clang -framework CoreFoundation -framework CoreGraphics -framework IOKit ./HID.c -o hid
//    ./hid

#include <IOKit/hid/IOHIDValue.h>
#include <IOKit/hid/IOHIDManager.h>
#include <ApplicationServices/ApplicationServices.h>

CFMutableDictionaryRef myCreateDeviceMatchingDictionary(UInt32 pUsagePage, UInt32 pUsage)
{
    CFMutableDictionaryRef matchDict = CFDictionaryCreateMutable(kCFAllocatorDefault, 1, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
    CFNumberRef usagePage = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &pUsagePage);
    CFNumberRef usage = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &pUsage);
    if (matchDict && usagePage && usage) {
        CFDictionarySetValue(matchDict, CFSTR(kIOHIDDeviceUsagePageKey), usagePage);
        CFDictionarySetValue(matchDict, CFSTR(kIOHIDDeviceUsageKey), usage);
        CFRelease(usagePage);
        CFRelease(usage);
        return matchDict;
    }
    return 0;
}

CFMachPortRef eventTap;
CFRunLoopTimerRef disableTimer;

static void TimerCallback(CFRunLoopTimerRef timer, void *info)
{
    printf("disabling CGEventTap\n");
    CGEventTapEnable(eventTap, false);
    CFRelease(disableTimer);
    disableTimer = NULL;
}

static CGEventRef EventTapCallback(CGEventTapProxy proxy, CGEventType type, CGEventRef eventRef, void *_Nullable userInfo)
{
    printf("EventTapCallback type:%d\n", type);
    if (type != -1) {
        if (disableTimer) {
            CFRunLoopRemoveTimer(CFRunLoopGetCurrent(), disableTimer, kCFRunLoopDefaultMode);
            CFRelease(disableTimer);
            disableTimer = NULL;
        }
        CFRunLoopTimerContext timerContext = {0, NULL, NULL, NULL, NULL};
        disableTimer = CFRunLoopTimerCreate(kCFAllocatorDefault,
                         // 50ms is just a guess. One iteration with CFRunLoopPerformBlock was not enough
                         CFAbsoluteTimeGetCurrent() + 0.050,
                         0, 0, 0,
                         TimerCallback,
                         &timerContext);
        CFRunLoopAddTimer(CFRunLoopGetCurrent(), disableTimer, kCFRunLoopDefaultMode);
    }
    return eventRef;
}

static void hidInputReportCallback(void *context, IOReturn result, void *sender, IOHIDReportType type,
                                   uint32_t reportID, uint8_t *reportValue, CFIndex reportLength)
{
    IOHIDDeviceRef device = (IOHIDDeviceRef)sender;
    CFTypeRef name = IOHIDDeviceGetProperty(device, CFSTR(kIOHIDProductKey));
    printf("Device `%s`: ", CFStringGetCStringPtr(name, kCFStringEncodingUTF8));
    for (int i = 0 ; i < reportLength; i++) {
        printf("%3d ", (char)reportValue[i]);
    }
    printf("\nEnabling CGEventTap\n");
    CGEventTapEnable(eventTap, true);
}

int main(void)
{
    IOHIDManagerRef hidManager = IOHIDManagerCreate(kCFAllocatorDefault, kIOHIDOptionsTypeNone);

    // found from: ioreg -irc IOHIDDevice -w 0
    CFMutableDictionaryRef touchbar = myCreateDeviceMatchingDictionary(13, 5);
    CFMutableDictionaryRef touchbar2 = myCreateDeviceMatchingDictionary(65280, 35);
    CFMutableDictionaryRef touchbar3 = myCreateDeviceMatchingDictionary(65280, 22);

    CFMutableDictionaryRef matchesList[] = {touchbar3};

    CFArrayRef matches = CFArrayCreate(kCFAllocatorDefault, (const void **)matchesList, sizeof(matchesList)/sizeof(matchesList[0]), NULL);

    IOHIDManagerSetDeviceMatchingMultiple(hidManager, matches);
    IOHIDManagerRegisterInputReportCallback(hidManager, hidInputReportCallback, NULL);
    IOHIDManagerScheduleWithRunLoop(hidManager, CFRunLoopGetMain(), kCFRunLoopDefaultMode);
    IOHIDManagerOpen(hidManager, kIOHIDOptionsTypeNone);

    eventTap = CGEventTapCreate(kCGSessionEventTap, kCGHeadInsertEventTap, 0, kCGEventMaskForAllEvents, EventTapCallback, NULL);
    CFRunLoopSourceRef runLoopSource = CFMachPortCreateRunLoopSource(kCFAllocatorDefault, eventTap, 0);
    if (runLoopSource) {
        CFRunLoopAddSource(CFRunLoopGetMain(), runLoopSource, kCFRunLoopDefaultMode);
        CGEventTapEnable(eventTap, false);
    }

    CFRunLoopRun();
}