c++ - 通过写入std::cout影响虚拟键码到unicode的映射？

我遇到了一个奇怪的问题，我真的不知道该如何解决。我正在用C++编写代码，该代码应该在按下键时触发事件。我可以使用GetAsyncKeystate来检测按键并释放良好，但是我无法可靠地将检测到的按键状态转换为unicode。 (请注意，我正在使用Qt，但这并不重要)

我的新闻/发布检测:

// This function is called in a loop
void KeyboardApi::Check()
{
    bool stat = false;
    for (int i = 7; i < 255; i++) { // 0 undefined, 3 VK_CANCEL can be ignored, 1 2 4 5 6 mouse keys, these are ignored
        stat = ((GetAsyncKeyState(i) & 0x8000) != 0);

        if (this->first_time) { // To prevent reporting keypresses upon initialization
            this->first_time = false;
            this->keystate[i] = stat;
            continue;
        }

        if (stat != this->keystate[i]) {
            this->keystate[i] = stat;

            if (i == VK_SHIFT)
                this->shift = stat;
            else if (i == VK_CONTROL)
                this->ctrl = stat;
            else if (i == VK_MENU)
                this->alt = stat;

            HKL locale = GetKeyboardLayout(GetCurrentThreadId());

            // ---!! If this portion is commented, the code does not work correctly.
            //       if this portion is *not* commented, the code works fine...
            /*
            std::wcout << "args for keycode_to_unicode:" << std::endl
                       << "  keycode: " << i << std::endl
                       << "  locale: " << locale << std::endl
                       << "  shift: " << this->shift << std::endl;
            */
            // ---!!

            QString key_string = keycode_to_unicode(i, locale, this->shift);

            if (stat)
                std::wcout << "Key pressed:  " << i <<  " unicode: " << key_string.toStdWString() << std::endl;
        }
    }
}

和keycode_to_unicode函数:

QString keycode_to_unicode(unsigned int key, HKL keyboardLayoutHandle, bool shiftPressed)
{
    int scanCodeEx = MapVirtualKeyExW(key, MAPVK_VK_TO_VSC_EX, keyboardLayoutHandle);

    if (scanCodeEx > 0) {
        unsigned char lpKeyState[256];

        if (shiftPressed) {
            lpKeyState[VK_SHIFT] = 0x80;
            lpKeyState[VK_LSHIFT] = 0x80;
        }

        wchar_t buffer[5];

        int rc = ToUnicodeEx(key, scanCodeEx, lpKeyState, buffer, 5, 0, keyboardLayoutHandle);

        if (rc > 0) {
            return QString::fromWCharArray(buffer);
        } else {
            // It's a dead key; let's flush out whats stored in the keyboard state.
            rc = ToUnicodeEx(key, scanCodeEx, lpKeyState, buffer, 5, 0, keyboardLayoutHandle);
            return QString();
        }
    }

    return QString();
}

所以奇怪的是，当我在那里有调试输出时，KeyboardApi::Check()可以正常工作，但是当我没有调试输出时，向Unicode的转换就会出错。例如，当我第一次按“A”键时，将输出“a”。第二次，“β”，“β”等。

编辑:
您可能会问自己为什么我不使用Qt的内置onKeyPress ...这是因为我的代码已注入(inject)到其他进程中，所以我不能使用这种方法。

最佳答案

原来是keycode_to_unicode的问题!

在我的代码中，我有:

unsigned char lpKeyState[256];

这意味着该数组未初始化；它的内容可以是任何东西。替换为:

unsigned char lpKeyState[256] = {0};

修复了奇数输入的问题。原来我还有其他一些问题(特别是死键)。我对代码进行了一些更改，现在可以在按下死键时正确检测死键，尽管我还没有成功地将死键与后续字符结合起来以检测带有重音符号的字符。为了完整起见，下面是修改后的代码:

注意:它不考虑大写锁定。

QString KeyboardApi::keycode_to_unicode(unsigned int key, HKL keyboardLayoutHandle, bool shiftPressed, bool ctrlPressed, bool altPressed, bool capslock)
{
    int scanCodeEx = MapVirtualKeyExW(key, MAPVK_VK_TO_VSC_EX, keyboardLayoutHandle);

    if (scanCodeEx <= 0)
        return QString();

    unsigned char lpKeyState[256] = {0};

    if (shiftPressed) {
        lpKeyState[VK_SHIFT] = 0x80;
        lpKeyState[VK_LSHIFT] = 0x80;
    }

    if (ctrlPressed)
        lpKeyState[VK_CONTROL] = 0x80;

    if (altPressed)
        lpKeyState[VK_MENU] = 0x80;

    if (capslock)
        lpKeyState[VK_CAPITAL] = 0x01;

    wchar_t buffer[5];

    ToUnicodeEx(key, scanCodeEx, lpKeyState, buffer, 5, 0, keyboardLayoutHandle);

    QString ret = QString::fromWCharArray(buffer);
    ret.truncate(1);

    return ret;
}

Qt::Key KeyboardApi::unicode_to_qtkey(QString key)
{
    unsigned int code = key[0].unicode();
    if (key[0].unicode() >= 'a' && key[0].unicode() <= 'z') {
        code = key[0].unicode() - 'a' + Qt::Key_A;
    }

    return (Qt::Key)code;
}

void KeyboardApi::Check()
{
    bool init = this->first_time;

    if (this->first_time)
        this->first_time = false;

    bool stat = false;
    for (int i = 7; i < 255; i++) { // yes, 255 is NOT valid! // 0 undefined, 3 VK_CANCEL can be ignored, 1 2 4 5 6 mouse keys
        stat = ((GetAsyncKeyState(i) & 0x8000) != 0);

        if (stat == this->keystate[i])
            continue;

        this->keystate[i] = stat;

        if (i == VK_SHIFT)
            this->shift = stat;
        else if (i == VK_CONTROL)
            this->ctrl = stat;
        else if (i == VK_MENU)
            this->alt = stat;
        else if (i == VK_CAPITAL)
            this->capslock = stat;

        HKL locale = GetKeyboardLayout(GetCurrentThreadId());

        QString key_string = keycode_to_unicode(i, locale, this->shift, this->ctrl, this->alt, false);

        // See qkeymapper_win.cpp for the table used to convert windows virtual key codes to Qt::Key
        Qt::Key key = key_string.isEmpty() ? (Qt::Key)win_vk_to_qt_key[i] : unicode_to_qtkey(key_string);

        if (init || i == VK_SHIFT || i == VK_CONTROL || i == VK_MENU)
            continue;

        if (stat) {
            emit this->OnKeyDown(this, QKeyEvent(QEvent::KeyPress, key, mods, key_string));
        } else
            emit this->OnKeyUp(this, QKeyEvent(QEvent::KeyPress, key, mods, key_string));
    }
}

关于c++ - 通过写入std::cout影响虚拟键码到unicode的映射？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/24955875/