[DejaVu-bugs] [Bug 47339] New: ISO 15919 transliteration of Indic vocalic R/RR/L/LL not displayed properly in DejaVu fonts

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Thu Mar 15 02:23:22 PDT 2012


https://bugs.freedesktop.org/show_bug.cgi?id=47339

             Bug #: 47339
           Summary: ISO 15919 transliteration of Indic vocalic R/RR/L/LL
                    not displayed properly in DejaVu fonts
    Classification: Unclassified
           Product: DejaVu
           Version: unspecified
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: General
        AssignedTo: dejavu-bugs at lists.freedesktop.org
        ReportedBy: samjnaa at gmail.com


Created attachment 58478
  --> https://bugs.freedesktop.org/attachment.cgi?id=58478
ZIP of ODT containing relevant text, PDFs showing current rendering and TTF of
sample glyphs

Using DejaVu fonts 2.33.

In the ISO 15919 transliteration standard for Indic scripts, R and L with ring
below, and the same with macron above (and ring below) are prescribed for
transliterating the so-called vocalic R/RR/L/LL characters (as per Unicode
parlance) of Indic scripts. See
http://homepage.ntlworld.com/stone-catend/trimain1.htm

However these are also among the written forms that do not have a pre-composed
Unicode character as you can see in
http://homepage.ntlworld.com/stone-catend/trinoun1.gif

The rest of the characters (which are having tilde) in the above chart are not
of primary importance as they are only for nasalized vowels which are very rare
and as such not listed in the transliteration chart linked first. But the
vocalic R/RR/L/LL are quite important for Sanskrit/Vedic. As such it is
important for the DejaVu fonts to support them correctly.

However, I have tested the latest DejaVu fonts on LibreOffice 3.5 (latest) on
Windows XP (sorry I don't use the latest) and Kubuntu Oneiric (latest
released). The fonts exhibit various degrees of supporting the ISO-prescribed
sequences, and what's more the rendering on Windows is different from (i.e.
worse than) the rendering on Linux. 

Mono has the worst behaviour with overlappings on Windows and misplacement of
diacritics on Linux. Sans and Serif don't place the macron above the base (see
small L, capital R/L) on Linux whereas they seem to do so on Windows. 

As for lesser problems:

Sans and Serif also don't position the ring correctly centered below small l
and capital R. Sans also doesn't center the macron correctly above the base in
small R/L and capital R. (Placing the macron centered above the vertical stroke
of capital L is acceptable.)

As a general solution to all above problems, I would recommend following the
diacritic placements of the unified precomposed characters 1E5C Ṝ 1E5D ṝ 1E38 Ḹ
1E39 ḹ (used for the same purpose in the alternate IAST transliteration scheme
for Sanskrit). The ring should merely replace the dot below. I have included a
sample TTF from the regular versions of all three fonts.

Now it is up to you whether you are going to add a pre-composed unmapped glyph
following that placement and do a GSUB substitution mapping to that glyph
(easier?) or whether you actually position the diacritics correctly using the
GPOS table or such (more difficult?). 

In any case, it would be great if you could support these characters which are
very important for us for Indic transliteration. Thank you!

P.S.:

FWIW I checked the other multiple-character ISO 15919 written forms listed at
http://homepage.ntlworld.com/stone-catend/trinoun2.gif and
http://homepage.ntlworld.com/stone-catend/trinoun4.gif:
M̐m̐H̱N̆n̆M̆m̆R̆r̆S̱s̱H̤h̤S̤s̤T̤t̤ and they seem to work correctly with all
three fonts.

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