Choosing font for GTK+ applications with KDE Settings -> Application style -> GNOME Application Style (GTK) -> GTK Themes:
if I choose font with font style written not with english (latin) characters, then KDE writes it in a file with settings
/home/MyName/.config/gtk-3.0/settings.ini
in UTF8 string coding:
gtk-font-name=Bitstream Charter Regular 11
but
gtk-font-name=Courier New \xd0\x9e\xd0\xb1\xd1\x8b\xd1\x87\xd0\xbd\xd1\x8b\xd0\xb9 11
Here
“\xd0\x9e\xd0\xb1\xd1\x8b\xd1\x87\xd0\xbd\xd1\x8b\xd0\xb9” = “Обычный”.
Decoding: http://ddecode.com/hexdecoder/
If program uses GTK+, then it cannot get neither font style, nor font size.
It is possible to correct it by hands and get what we expext:
gtk-font-name=Courier New Обычный 11