Style: when and to what extent to re-use glyphs between scripts

[Paul Sladen]

(Tracking bug to keep general conversation off bug #609289 and bug #647092).

Various glyphs are re-used between multiple codepoints; this occurs when a glyph is used as the (only) component of another glyph, with only position, or scaling changes. For example Latin M ('M'), Cyrillic Em ('М') and Greek Mu ('Μ'), are all the same glyph. And this is the case for many characters common between the three scripts:

  A: afii10017,Alpha
  B: afii10019,Beta
  E: afii10022,Epsilon
  I: uni04CF,uni04C0,afii10055,Iota
  H: afii10031,Eta
  K: afii10028,Kappa
  M: afii10030,Mu
  O: afii10032,Omicron
  P: afii10034,Rho
  T: afii10036,Tau
  Y: uni04AE,Upsilon
  X: afii10039,Chi (bug 647092)
  o: afii10080,omicron
  x: afii10087,chi
  ...

In Ubuntu Font Family 0.68, there are roughly 80 base glyphs that are directly re-used, on average two times each. Note that a large proportion of these are simply numeric digit aliasing for superiors/inferiors/super- and sub-script.

  $ for i in ubuntu-private-fonts-0.68.orig/Ubuntu*.ttf ; do echo -n $i': ' ; ./glyph-reuse.py $i | wc -l ; done
  ubuntu-private-fonts-0.68.orig/UbuntuBdIt.ttf: 82
  ubuntu-private-fonts-0.68.orig/UbuntuBd.ttf: 82
  ubuntu-private-fonts-0.68.orig/UbuntuIt.ttf: 85
  ubuntu-private-fonts-0.68.orig/UbuntuRg.ttf: 79

See/take/use/extend the attached Python script for further analysis (sudo apt-get install fonttools).

[Paul Sladen (sladen)]

Output from Ubuntu Font Family 0.68 Regular/Bold/Italic/BoldItalic for ease-of-reference:

[Paul Sladen (sladen)]

Minor tweak to the script with slightly more pleasant sorting in the output.

[adoa (adoa)]

The glyph reuse is actually so common, that in most cases these characters are not used at the same time. Only Greek chi and Latin x and latin v and greek nu are used side by side in mathematical contexts since in most fonts they have different glyphs.

cf https://en.wikipedia.org/wiki/Greek_letters_used_in_mathematics

[Matthew Paul Thomas (mpt)]

This is an interesting summary of duplicate glyphs. Maybe the duplicate-finder should be included with Fontforge or some other font-development package? And/or maybe the list of duplicates should be documented in the Ubuntu font source package. If so, please reopen this bug report for that.

In the meantime, though, this bug report doesn't seem to describe a particular problem (which bug #609289 and bug #647092, whether valid or not, both do). Does the existence of duplicates at all suggest a problem (like a lack of code reuse)? Does the differing number of duplicates between variants indicate a problem?

[Launchpad Janitor (janitor)]

[Expired for Ubuntu Font Family because there has been no activity for 60 days.]