Kerning: '2G' in 'Linux2Go' appears to be spaced

[harry snotter]

Sample Glyphs:

x2G

Description:

My company is called Linux2Go. I have a separate e-mail account for it which is cleverly titled "Linux2Go" in my e-mail client. When I opened my e-mail client (having configured my desktop to use the new font everywhere by default) today and I saw "Linux2Go" I actually thought I'd accidentally put a space in between "Linux2" and "Go". Upon further inspection, it turns out that I didn't. I can't really tell if it's 'x' and '2' that are too close or if it's '2' and 'G' that are too far apart, but it really looks like there's an extra space there. I'm attaching a screenshot so that you can see for yourself.

UA String:

Mozilla/5.0 (X11; U; Linux x86_64; da-DK; rv:1.9.2.6) Gecko/20100628 Ubuntu/10.04 (lucid) Firefox/3.6.6

[Paul Sladen (sladen)]

Please could you attach a screenshot showing the spacing of the sequence 'Linux2Go' on the system that you've seen the issue with.

[Vincent Connare (vince-daltonmaag)]

The reason you are seeing this problem is that the standard figures in Ubuntu Sans are tabularly spaced figures. Meaning they are all on the same advance width as the figure zero. This is necessary for setting figures in consistent columns.

There are also proportionally spaced figures that are in the private use area of Unicode and can be accessed in OpenOffice with the menuitem Insert/Special Characters..then from the dropdown menu select 'Private Use' which and the glyphs with the unicode values of xF800..F809 are the proportional numerals.

There is also an OpenType feature in the font that applications that support OpenType fully can access.

regards,

Vincent Connare
DaltonMaag Ltd.

enc. png of the Linux2Go with tabular and proportional number 2.

[Tobias Wolf (towolf)]

Vincent, you really should be testing with the default font settings in Ubuntu. We don’t default to monochrome superhinting, we use the FreeType light autohinter and LCD filtering.

[Vincent Connare (vince-daltonmaag)]

LCD Subpixel 96dpi

[Paul Sladen (sladen)]

Vincent et al: even if the default of tabular width numerals, AFAICT, it should still be possible to /kern/ those against particularly combinations of letters where they don't look great.

How does kerning interact with alternates? Eg. if the features=pnum is choosen, will the same kerning set as for features=tnum be used?

[David Marshall (dave-daltonmaag)]

The following also applies to Bug 793074:

Yes, it's physically possible to kern every character against every
other character - the problem is that OpenType has a limit on the
maximum number of traditional kern pairs (in the "kern" table), so as a
character set gets larger you have to become increasingly selective
about which pairs you include, and which you ignore.

The solution is, of course, class-based kerning using GPOS, which allows
perfect kerning of everything against everything else, with minimal file
overhead, but that requires the text layout library to "do the right
thing" with the OpenType features.

Kerning is glyph-against-glyph, not character-against-character, so
alternate characters, substitutions etc. can still be handled properly.

Dave