[Fontconfig] Firefox & Typeface Selection

[Raimund Steger]

Jorge Fábregas wrote:
> [...]
> Their new CSS font-family property is:
> "Helvetica Neue", Helvetica, Arial, sans-serif;
> [...]
>
> When I go to Wikipedia, the actual font being rendered is "Nimbus Sans
> L" (confirmed by various Firefox addons I have).  This is the 2nd option
> in the CSS property (Helvetica).
>
> My question is:  Since I don't have any of these typefaces, why is the
> 2nd option being selected & not the 1st one (Helvetica Nueue)?  Is there
> some notion of "preference" in fontconfig? Or is it a Firefox issue?
> That is,  Firefox decided to use the 2nd option and asked fontconfig for it?

What does

   FC_DEBUG=1 fc-match "Helvetica Neue, Helvetica, Arial, sans-serif"

give you? (It is unlikely that Firefox executes several distinct 
FcFontMatch calls as in your example)

The above command prints the full pattern (with the family names you 
gave) after config substitution (i. e. after fontconfig executes all 
"pattern" rules that occur in your configuration files), as well as the 
font that gets the best score. Maybe the substituted pattern already 
tells you why Nimbus Sans L is used with higher precedence on your 
machine. I would guess that Deja Vu Sans is only used as "default" 
fallback, hence it has not a very prominent position in the substituted 
pattern.

Raimund

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