QFont: More Fine Grained Font Substitution

It would be really nice if there was more fine-grained control of font
substitution in Qt. With QFont, you can set a substitute font to be used
if a given Unicode character isn't found in a certain font.

it would be very helpful if substitute fonts could be set based
on unicode ranges rather than just if a font doesn't have a character.
Thus, I would like to be able to use Font1 in the Unicode range of
0000-00FF (the Latin range), use Font2 in the Unicode range of 0600-07FF
(Arabic), use Font3 in the Unicode range of 0590-05FF (Hebrew), etc. Of
course you could still have ordering if the ranges overlap, characters are
missing, etc.