Comment 1 for bug 813373

No news on this?
For me the bug lies in the fonts properties.
Doing for example:
$ fc-query /usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-M.ttf

the Medium variant (and the Light also) report double values on some properties, like this:

family: "Ubuntu"(s) "Ubuntu Medium"(s)
familylang: "en"(s) "en"(s)
style: "Medium"(s) "Bold"(s)
stylelang: "en"(s) "en"(s)
fullname: "Ubuntu Medium"(s)
fullnamelang: "en"(s)
slant: 0(i)(s)
weight: 100(i)(s)

I don't know what the '(s)' stands for.
Probably that 'Bold' on the style property is misinterpreted by some programs, that cannot distinguish between this and the true Bold, using only the first (or last) variant read, that seems to be "Medium".

This is an example how Helvetica Neue sets those properties:

family: "Helvetica Neue"(s)
style: "中黑"(s) "Medium"(s) "Halbfett"(s) "Moyen"(s) "Medio"(s) "ミディアム"(s) "중간체"(s) "Médio"(s) "Средний"(s) "Medel"(s) "中等"(s) "متوسط"(s) "Media"(s)
stylelang: "zh-tw"(s) "da"(s) "de"(s) "fr"(s) "it"(s) "ja"(s) "ko"(s) "pt"(s) "ru"(s) "sv"(s) "zh-cn"(s) "ar"(s) "es"(s)
slant: 0(i)(s)
weight: 100(i)(s)

It declares only one family, and various styles seems to correspond to various languages. I can see correctly each variant this way (in the few programs that I use), but he suffers bug #744812 too (like probably every font family that has more than 5 variants or doesn't set the 'weight' property the way Qt requires).

While waiting for a fix, I workaround-ed this problem with fontconfig (file attached), moving the Light and Medium variants in a new family called "Ubuntu Light", where Medium is the 'Light Bold'.
This way Regular and Bold are listed under "Ubuntu" family, while Light and Medium are listed under "Ubuntu Light" family, and each variant shows up correctly.
But it's only a "concept patch", as this workaround probably needs more fine-tuning (for example, the involved fonts name in Gimp are a bit weird).