MacOS Media Key Press Emulation

main.m

@import CoreGraphics;

static const CGEventField kCGEventSubtype = 0x53;
static const CGEventField kCGEventData1 = 0x95;
static const CGEventField kCGEventData2 = 0x96;

static CGEventRef CGEventCreateMediaKeyEvent(CGEventSourceRef _Nullable source, int64_t key, BOOL down) {
    CGEventFlags flags = (down ? NX_KEYDOWN : NX_KEYUP) << 8;

    CGEventRef e = CGEventCreate(source);
    CGEventSetType(e, NX_SYSDEFINED);
    CGEventSetFlags(e, flags);
    CGEventSetIntegerValueField(e, kCGEventSubtype, NX_SUBTYPE_AUX_CONTROL_BUTTONS);
    CGEventSetIntegerValueField(e, kCGEventData1, flags | (key << 16));
    CGEventSetIntegerValueField(e, kCGEventData2, -1);
    return e;
}

static void PostKey(CGEventSourceRef _Nullable source, uint64_t key) {
    {
        CGEventRef e = CGEventCreateMediaKeyEvent(source, key, YES);
        CGEventPost(kCGHIDEventTap, e);
        CFRelease(e);
    }
    {
        CGEventRef e = CGEventCreateMediaKeyEvent(source, key, NO);
        CGEventPost(kCGHIDEventTap, e);
        CFRelease(e);
    }
}

int main(int argc, const char * argv[]) {
    CGEventSourceRef source = CGEventSourceCreate(kCGEventSourceStateHIDSystemState);
    PostKey(source, NX_KEYTYPE_SOUND_UP);
    CFRelease(source);
    return 0;
}