使用 IOHIDManager 获取修改键事件

Question

我正在尝试使用 IOHIDManager 来获取修饰键事件，因为缺少 Cocoa flagsChanged 事件（很难区分按下/释放、左/右（如果两者都按下）等）这是我创建管理器并注册回调的代码。

IOHIDManagerRef hidManager = IOHIDManagerCreate(kCFAllocatorDefault,
        kIOHIDOptionsTypeNone);
if (CFGetTypeID(hidManager) != IOHIDManagerGetTypeID())
    return 1;

CFMutableDictionaryRef capsLock =
    myCreateDeviceMatchingDictionary(0x07, 0x39);
CFMutableDictionaryRef lctrl =
    myCreateDeviceMatchingDictionary(0x07, 0xE0);
CFMutableDictionaryRef lshift =
    myCreateDeviceMatchingDictionary(0x07, 0xE1);
CFMutableDictionaryRef lalt =
    myCreateDeviceMatchingDictionary(0x07, 0xE2);
CFMutableDictionaryRef lsuper =
    myCreateDeviceMatchingDictionary(0x07, 0xE3);
CFMutableDictionaryRef rctrl =
    myCreateDeviceMatchingDictionary(0x07, 0xE4);
CFMutableDictionaryRef rshift =
    myCreateDeviceMatchingDictionary(0x07, 0xE5);
CFMutableDictionaryRef ralt =
    myCreateDeviceMatchingDictionary(0x07, 0xE6);
CFMutableDictionaryRef rsuper =
    myCreateDeviceMatchingDictionary(0x07, 0xE7);

CFMutableDictionaryRef matchesList[] = {
    capsLock,
    lctrl,
    lshift,
    lalt,
    lsuper,
    rctrl,
    rshift,
    ralt,
    rsuper
};
CFArrayRef matches = CFArrayCreate(kCFAllocatorDefault,
        (const void **)matchesList, 9, NULL);
IOHIDManagerSetDeviceMatchingMultiple(hidManager, matches);

IOHIDManagerRegisterInputValueCallback(hidManager,
        myHandleModifiersCallback, NULL);

IOHIDManagerScheduleWithRunLoop(hidManager, CFRunLoopGetMain(),
        kCFRunLoopDefaultMode);

IOHIDManagerOpen(hidManager, kIOHIDOptionsTypeNone);

但是，回调永远不会运行。我错过了什么吗？

我不完全了解 HID 使用页面，因此我不知道是否使用带有键盘使用 ID (06) 的通用桌面页面 (0x01) 或带有个人使用 ID 的键盘/小键盘页面 (0x07)键。也许这有什么关系？

Answer 1

我想通了。实现方法是使用通用桌面页面 (0x01) 键盘 (06)（为了完整起见，还使用小键盘 (07)）与 IOHIDManagerSetDeviceMatchingMultiple 一起使用，然后输入值回调获取键盘/小键盘使用页面 (0x07) 内容。

例如，要为所有键盘/小键盘设置 HIDManager，可以执行以下操作：

IOHIDManagerRef hidManager = IOHIDManagerCreate(kCFAllocatorDefault,
        kIOHIDOptionsTypeNone);

CFMutableDictionaryRef keyboard =
    myCreateDeviceMatchingDictionary(0x01, 6);
CFMutableDictionaryRef keypad =
    myCreateDeviceMatchingDictionary(0x01, 7);

CFMutableDictionaryRef matchesList[] = {
    keyboard,
    keypad,
};
CFArrayRef matches = CFArrayCreate(kCFAllocatorDefault,
        (const void **)matchesList, 2, NULL);
IOHIDManagerSetDeviceMatchingMultiple(hidManager, matches);

IOHIDManagerRegisterInputValueCallback(hidManager,
        myHIDKeyboardCallback, NULL);

IOHIDManagerScheduleWithRunLoop(hidManager, CFRunLoopGetMain(),
        kCFRunLoopDefaultMode);

IOHIDManagerOpen(hidManager, kIOHIDOptionsTypeNone);

其中 myCreateDeviceMatchingDictionary 类似于：

CFMutableDictionaryRef myCreateDeviceMatchingDictionary(UInt32 usagePage,
        UInt32 usage) {
    CFMutableDictionaryRef ret = CFDictionaryCreateMutable(kCFAllocatorDefault,
            0, &kCFTypeDictionaryKeyCallBacks,
            &kCFTypeDictionaryValueCallBacks);
    if (!ret)
        return NULL;

    CFNumberRef pageNumberRef = CFNumberCreate(kCFAllocatorDefault,
            kCFNumberIntType, &usagePage );
    if (!pageNumberRef) {
        CFRelease(ret);
        return NULL;
    }

    CFDictionarySetValue(ret, CFSTR(kIOHIDDeviceUsagePageKey), pageNumberRef);
    CFRelease(pageNumberRef);

    CFNumberRef usageNumberRef = CFNumberCreate(kCFAllocatorDefault,
            kCFNumberIntType, &usage);
    if (!usageNumberRef) {
        CFRelease(ret);
        return NULL;
    }

    CFDictionarySetValue(ret, CFSTR(kIOHIDDeviceUsageKey), usageNumberRef);
    CFRelease(usageNumberRef);

    return ret;
}

而 myHIDKeyboardCallback 类似于：

void myHIDKeyboardCallback(void *context, IOReturn result, void *sender,
        IOHIDValueRef value) {
    IOHIDElementRef elem = IOHIDValueGetElement(value);
    if (IOHIDElementGetUsagePage(elem) != 0x07)
        return;
    uint32_t scancode = IOHIDElementGetUsage(elem);
    if (scancode < 4 || scancode > 231)
        return;
    long pressed = IOHIDValueGetIntegerValue(value);
    // ... Do something ...
}

请注意，每次按下或释放时，回调似乎都会被调用多次，但带有使用 ID超出正常范围，这就是“if (scancode < 4 || scancode > 231)”的作用。

Answer 2

感谢您回答您的问题。

您可以使用 IOHIDManagerSetInputValueMatching，而不是 myHIDKeyboardCallback 中检查 scancode<4 或 scancode>231 的 if 语句。

// before IOHIDManagerOpen
int usageMin = 4;
CFNumberRef minNumberRef = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &usageMin);
CFDictionarySetValue(inputValueFilter, CFSTR(kIOHIDElementUsageMinKey), minNumberRef);
CFRelease(minNumberRef);

int usageMax = 231;
CFNumberRef maxNumberRef = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &usageMax);
CFDictionarySetValue(inputValueFilter, CFSTR(kIOHIDElementUsageMaxKey), maxNumberRef);
CFRelease(maxNumberRef);

IOHIDManagerSetInputValueMatching(hidManager, inputValueFilter);

它比简单的 if 语句更具 LOC，但最终会得到一个更清晰的回调。