hidcode.c

#include <IOKit/hid/IOHIDLib.h>
#include <IOKit/hidsystem/event_status_driver.h>

static int hid_mousex, hid_mousey;

static void hidCallback(void* context, IOReturn result, void* sender, IOHIDValueRef valueRef)
{
    IOHIDElementRef element = IOHIDValueGetElement(valueRef);
    if (mouse_capture > 0 && IOHIDElementGetUsagePage(element) == kHIDPage_GenericDesktop) {
        int value = (int)IOHIDValueGetIntegerValue(valueRef);
        switch (IOHIDElementGetUsage(element)) {
        case kHIDUsage_GD_X:
            hid_mousex += value;
            break;
        case kHIDUsage_GD_Y:
            hid_mousey += value;
            break;
        }
    }
}

... init ...

    sys_log(SYSLOG_NONE, "Initializing the HID manager");
    hidManager = IOHIDManagerCreate(kCFAllocatorSystemDefault, kIOHIDOptionsTypeNone);
    if (!hidManager) {
        sys_log(SYSLOG_FATAL, "Failed to initialize the HID manager");
        eng_shutdown();
        return 0;
    }

    sys_log(SYSLOG_NONE, "Initializing the HID callbacks");
    IOHIDManagerSetDeviceMatching(hidManager, NULL);
    IOHIDManagerRegisterInputValueCallback(hidManager, hidCallback, NULL);
    IOHIDManagerScheduleWithRunLoop(hidManager, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
    if (IOHIDManagerOpen(hidManager, kIOHIDOptionsTypeNone) != kIOReturnSuccess) {
        sys_log(SYSLOG_FATAL, "Failed to open the HID manager");
        eng_shutdown();
        return 0;
    }

... shutdown ...

    IOHIDManagerUnscheduleFromRunLoop(hidManager, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
    CFRelease(hidManager);

... main loop ...

    if (hid_mousex) {
        eng_key(KEY_MOUSE_X, hid_mousex);
        hid_mousex = 0;
    }
    if (hid_mousey) {
        eng_key(KEY_MOUSE_Y, hid_mousey);
        hid_mousey = 0;
    }