QFile::open(int fd, ...) refers to 'raw' mode

https://doc.qt.io/qt-5/qfile.html#open-2

The QFile that is opened using this function is automatically set to be in raw mode; this means that the file input/output functions are slow. If you run into performance issues, you should try to use one of the other open functions.

1. IO_Raw is a mode from Qt3
2. The statement seems to be wrong - the QIODevice is always opened with `mode` unchanged:
   https://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/io/qfile.cpp#n1044