Technical: Medium and Bold both have WeightClass=700

This is something we do to work round a bug in HP printer drivers, which
we first identified in around 2001. Coincidentally we're just trying to
establish internally whether we still need to do this - whether clients
are still likely to encounter buggy drivers out in the wild.

The driver bug was basically that any value above 700 would result in
the font being even further algorithmically emboldened by the printer -
with catastrophic results.

Dave

For Google Web Fonts, a medium weight has a value of 500, so I'm unsure why the decade old HP printer bug workaround is relevant :)

Here are the label:number weights Google Web Fonts uses:

Thin: 100
ExtraLight: 200
UltraLight: 200
Light: 300
Normal: 400
Regular: 400
Medium: 500
SemiBold: 600
DemiBold: 600
Bold: 700
ExtraBold: 800
UltraBold: 800
Black: 900
Heavy: 900

Well, I couldn't say for sure that the bug has gone away or been fixed,
or that the affected drivers aren't still in widespread use. So I'd want
to exercise some caution, and do a bit of testing, before changing the
WeightClass.

Breaking the fonts for one combination of platform and printer
manufacturer while making them work for webfont provision would be a
step backwards.

Dave

David: I don't think that it needs to go above 700, but rather down to 500.

Sorry, yes, I managed to completely misread which weights we were
talking about (having just been discussing Black weights elsewhere,
which have this problem). The Medium should indeed be 500.

Dave

Add unittest for font weights to build setup:

  http://bazaar.launchpad.net/~sladen/ubuntu-font-family/midstream/revision/25

which currently gives a failure and so will catch it in the future:

  $ ./midstream/rules -k
  midstream/validate-weight.py 500 FinalFonts/UbuntuMd.ttf
    assert f['OS/2'].usWeightClass == int(weight)
  midstream/validate-weight.py 500 FinalFonts/UbuntuMdIt.ttf
    assert f['OS/2'].usWeightClass == int(weight)
  make: Target `all' not remade because of errors.

This a new upstream version of the Ubuntu Font Family. In addition to
the extensive bug fixes it doubles the number of .ttfs files, from four
to eight with the inclusion of Light, Medium and italics.

Upstream changelog:

2010-03-08 (Paul Sladen) Ubuntu Font Family version 0.71.2

* (Production) Adjust Medium WeightClass to 500 (Md, MdIt) (LP:
#730912)

2010-03-07 (Paul Sladen) Ubuntu Font Family version 0.71.1

* (Design) Add Capitalised version of glyphs and kern. (Lt, LtIt,
Md, MdIt) DM (LP: #677446)
* (Design) Re-space and tighen Regular and Italic by amount specified
by Mark Shuttleworth (minus 4 FUnits). (Rg, It) (LP: #677149)
* (Design) Design: Latin (U+0192) made straight more like l/c f with
tail (LP: #670768)
* (Design) (U+01B3) should have hook on right, as the lowercase
(U+01B4) (LP: #681026)
* (Design) Tail of Light Italic germandbls, longs and lowercase 'f'
to match Italic/BoldItalic (LP: #623925)
* (Production) Update <case> feature (Lt, LtIt, Md, MdIt). DM
(LP: #676538, #676539)
* (Production) Remove Bulgarian locl feature for Italics. (LP: #708578)
* (Production) Update Description information with new string:
"The Ubuntu Font Family are libre fonts funded by Canonical Ltd
on behalf of the Ubuntu project. The font design work and
technical implementation is being undertaken by Dalton Maag. The
typeface is sans-serif, uses OpenType features and is manually
hinted for clarity on desktop and mobile computing screens. The
scope of the Ubuntu Font Family includes all the languages used
by the various Ubuntu users around the world in tune with
Ubuntu's philosophy which states that every user should be able
to use their software in the language of their choice. The
project is ongoing, and we expect the family will be extended to
cover many written languages in the coming years."
(Rg, It, Bd, BdIt, Lt, LtIt, Md, MdIt) (LP: #690590)
* (Production) Pixel per em indicator added at U+F000 (Lt, LtIt, Md,
MdIt) (LP: #615787)
* (Production) Version number indicator added at U+EFFD (Lt, LtIt, Md,
MdIt) (LP: #640623)
* (Production) fstype bit set to 0 - Editable (Lt, LtIt, Md, MdIt)
(LP: #648406)
* (Production) Localisation of name table has been removed because
of problems with Mac OS/X interpretation of localisation. DM
(LP: #730785)
* (Hinting) Regular '?' dot non-circular (has incorrect control
value). (LP: #654336)
* (Hinting) Too much space after latin capital 'G' in 13pt
regular. Now reduced. (LP: #683437)
* (Hinting) Balance Indian Rupee at 18,19pt (LP: #662177)
* (Hinting) Make Regular '£' less ambiguous at 13-15 ppm (LP: #685562)
* (Hinting) Regular capital 'W' made symmetrical at 31 ppem (LP: #686168)