Convert string representation of keycode to Qt::Key (or any int) and back

You were already on the right track looking at QKeySequence, as this can be used to convert between string and key codes:

QKeySequence seq = QKeySequence("SPACE");
qDebug() << seq.count(); // 1

// If the sequence contained more than one key, you
// could loop over them. But there is only one here.
uint keyCode = seq[0]; 
bool isSpace = keyCode==Qt::Key_Space;
qDebug() << keyCode << isSpace;  // 32 true

QString keyStr = seq.toString().toUpper();
qDebug() << keyStr;  // "SPACE"

added by OP

The above does not support modifier keys such as Ctrl, Alt, Shift, etc. Unfortunately, QKeySequence does not acknowledge a Ctrl key by itself as a key. So, to support modifier keys, you must split the string representation using "+" sign and then process separately each substring. The following is the complete function:

QVector<int> EmoKey::splitKeys(const QString &comb)
{
    QVector<int> keys;
    const auto keyList = comb.split('+');
    for (const auto &key: keyList) {
        if (0 == key.compare("Alt", Qt::CaseInsensitive)) {
            keys << Qt::Key_Alt;
        } else if (0 == key.compare("Ctrl", Qt::CaseInsensitive)) {
            keys << Qt::Key_Control;
        } else if (0 == key.compare("Shift", Qt::CaseInsensitive)) {
            keys << Qt::Key_Shift;
        } else if (0 == key.compare("Meta", Qt::CaseInsensitive)) {
            keys << Qt::Key_Meta;
        } else {
            const QKeySequence keySeq(key);
            if (1 == keySeq.count()) {
                keys << keySeq[0];
            }
        }
    }
    return keys;
}