When QFont::fromString() in Qt 5.15 is used to read a description written with Qt 6, it fails because the number of values is too big (there is an explicit check for a maximum number of values in the code of QFont::fromString()).

The documentation for QFont::toString() states that a font description consists of 16 comma-separated values, and the documentation for QFont::fromString() states that it reads descriptions as returned by toString().

In Qt 5.15, however, only about 10 values are written and read.

It would be nice if in Qt5.15 ignore the additional fields and return a font that corresponds to the fields it recognizes.