Convert std::string to QString
QString::fromStdString(content) is better since it is more robust. Also note, that if std::string is encoded in UTF-8, then it should give exactly the same result as QString::fromUtf8(content.data(), int(content.size())).
There's a QString function called fromUtf8 that takes a const char*:
QString str = QString::fromUtf8(content.c_str());