See http://bugzilla.gnome.org/show_bug.cgi?id=334370 The Gimp has DejaVu ExtraLight renamed DejaVu UltraLight. Peeking at the code it seems UltraLight is just an alias for ExtraLight. Shouldn't they be different?
Here are some sample fonts: http://home.sus.mcgill.ca/~moyogo/fonts/test/ Jaja Thin, Light, Book, Medium, Demi, Bold, Black and Heavy. fc-list lists them as Jaja:style=Book Jaja:style=Bold Jaja:style=Light Jaja:style=Medium Jaja:style=Black Jaja:style=Heavy Jaja:style=Demi Jaja:style=Thin Applications get mixed up between some of them in different ways. Gimp has Black renamed Heavy, Heavy renamed Ultra-Bold, Demi renamed Semi-Bold, Thin renamed Ultra-Light, with Book and Medium sharing the same plain "Jaja" name. In the GTK font selector Medium is ordered before Book and displays the same weight.
Here's how the weight's are listed in the font properties in Fontlab and Fontforge: FontLab weights: Thin 100 UltraLight 200 ExtraLight 200 Light 300 Book 400 Regular 400 Normal 400 Medium 500 DemiBold 600 SemiBold 600 Bold 700 ExtraBold 800 Heavy 900 Black 900 Ultra 900 UltraBlack 900 Fat 1000 ExtraBlack 1000 Fontforge weights: Thin 100 Extra-Light 200 Light 300 Book 400 Medium 500 Demi-Bold 600 Bold 700 Heavy 800 Black 900 Note: Font weights names are not consistant across font families available.
Applications should not be using font weights to determine font styles. They should, instead, use the 'style' property. Unfortunately, most apps today do use font weight; in gimp's case, that would be pango's fault. See gnome bug 95043.
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