QStringList splitUnicodeString(const QString &str, quint32 limit)
{
    if (limit < 4) {
        qDebug() << "splitUnicodeString error: limit < 4";
        return QStringList();
    }
    QStringList result;
    std::u32string u32str = str.toStdU32String();

    quint32 len = 0;
    QString tmp;
    for (quint32 ch : u32str) {
        if (ch <= UCHAR_MAX) {
            if (len + 1 > limit) {
                result.push_back(tmp);
                tmp.clear();
                len = 1;
            } else {
                len += 1;
            }
        } else if (ch <= USHRT_MAX) {
            if (len + 2 > limit) {
                result.push_back(tmp);
                tmp.clear();
                len = 2;
            } else {
                len += 2;
            }
        } else if (ch <= UINT_MAX) {
            if (len + 4 > limit) {
                result.push_back(tmp);
                tmp.clear();
                len = 4;
            } else {
                len += 4;
            }
        }
        tmp.push_back(ch);
    }
    return result;
}

int main(int argc, char *argv[])
{
    qDebug() << splitUnicodeString("lol😀lolазазазаз", 7);