RUfl font substitution

[W P Blatchley]

Now I've expanded the repertoire of UCS fonts on my system, I'm wondering  
how RUfl decides from which fonts to take glyphs for substituting when  
they're not present in the font being painted with. Could someone explain,  
please? Is any attempt made to match styles and weights, and if so, how  
does RUfl determine the style and weight of a font?

TIA, WPB