[Bug 795327] New: Request to add Lohit Tamil Classical with old Tamil ligatures of -aa and -ai

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Mon Feb 20 09:25:11 UTC 2012


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Summary: Request to add Lohit Tamil Classical with old Tamil ligatures of -aa and -ai

https://bugzilla.redhat.com/show_bug.cgi?id=795327

           Summary: Request to add Lohit Tamil Classical with old Tamil
                    ligatures of -aa and -ai
           Product: Fedora
           Version: rawhide
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: unspecified
          Priority: unspecified
         Component: lohit-tamil-fonts
        AssignedTo: psatpute at redhat.com
        ReportedBy: samjnaa at gmail.com
         QAContact: extras-qa at fedoraproject.org
                CC: fonts-bugs at lists.fedoraproject.org,
                    psatpute at redhat.com, i18n-bugs at lists.fedoraproject.org
    Classification: Fedora
      Story Points: ---
              Type: ---
        Regression: ---
        Mount Type: ---
     Documentation: ---


Created attachment 564352
  --> https://bugzilla.redhat.com/attachment.cgi?id=564352
Lohit Tamil font v2.5.0 with name changed to Lohit Tamil Classical, and
additional glyphs added to PUA temporarily

Description of problem:

The Tamil script has a classical orthography in which the vowel sign -aa
ligates with the consonants ண NNA ன NNNA ற RRA and the vowel sign -ai ligates
with the consonants ண NNA ன NNNA ல LA ள LLA. 

Thus ணா னா றா (also seen in the right part of ணொ னொ றொ ணோ னோ றோ) and ணை னை லை
ளை would be presented differently. 

This classical style has been documented in the Unicode chapter on Tamil:
http://www.unicode.org/versions/Unicode6.0.0/ch09.pdf p 300 and 301 (in the
book, not of the PDF) under the name of "Ligatures with -aa in Traditional
Tamil Orthography" and "Ligatures with -ai in Traditional Tamil Orthography".

So far we are aware of only one Unicode Tamil font which supports it, e-Tamil
OTC by Elmar Kniprath from
http://www.aai.uni-hamburg.de/indtib/INDOLIPI/Indolipi.htm
(http://www.aai.uni-hamburg.de/indtib/INDOLIPI/Tamil.zip). You can check how
that font renders the text: ணா னா றா / ணொ னொ றொ / ணோ னோ றோ / ணை னை லை ளை.
However we especially like the visual style of Lohit Tamil so we wanted to do a
classical style Tamil font based on Lohit Tamil. 

So we have added the glyphs to the Lohit Tamil TTF font version 2.5.0 and
request to convert it into a Lohit Tamil Classical font to be separately
parallelly released apart from the Lohit Tamil font.

Version-Release number of selected component (if applicable):

2.5.0

How reproducible:

Install Lohit Tamil font. Type ணா னா றா / ணொ னொ றொ / ணோ னோ றோ / ணை னை லை ளை.

Actual results:

There are no ligatures of vowel signs -aa and -ai. This is CORRECT behaviour in
modern orthography but NOT in classical orthography.

Expected results:

The vowel signs -ai and -ai should ligate with the consonants as described
above.

Additional info:

The ligating presentation of the vowel sign -ai is colloquially called
"elephant's trunk ai" due to resemblance. After reordering the consonant and
-ai ை, the ை glyph can be replaced by the elephant's trunk glyph in contextual
substitution before NNA NNNA LA and LLA.

The metrics of the {elephant-ai} glyph should however be such that when it
simply replaces the regular {ai} glyph ை, it will correctly go and touch into
the nna ண nnna ன etc glyphs. Specifically, it will definitely have a negative
RSB. Currently we have determined that with an RSB of -118 it will look correct
and join with the following ண ன ல ள consonants correctly.

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