#65 OpenType 2005 'v.2' Indic script support ('dev2' etc)

v0.9999
closed
Khaled Hosny
5
2013-03-11
2012-03-27
Stevan White
No

Looks like XeTeX really has no functioning support for the 2005 v.2 Indic script tags.
(This was discovered in bug 3511113)

I've particularly investigated the Devanagari ones.

dev2: http://www.microsoft.com/typography/otfntdev/devanot/features.aspx
deva: http://www.microsoft.com/typography/OpenType%20Dev/devanagari/introO.mspx

dev2 adds

  • locl Localized form substitution
  • rkrf Rakaar form substitution NOTE a typo has 'pref' instead of 'rkrf'
  • cjct Conjunct form substitution
  • calt Contextual alternates
  • kern Kerning

Also, in dev2, 'dist' is applied after 'abvm' and 'blwm'.

Questions had arisen regarding a font that had specifications set to be activated
for either 'dev2' or 'deva'. I removed all the specifications of 'deva', and ran a test (attached)
which specified runs of script 'deva' and 'dev2'. Result: no lookups were activated for either
script tag.

Discussion

  • Stevan White
    Stevan White
    2012-03-27

    the test

     
    Attachments
  • Stevan White
    Stevan White
    2012-03-27

    result of test using font with only dev2 tags

     
  • Stevan White
    Stevan White
    2012-03-27

    result of test using font with deva and dev2 tags

     
  • Stevan White
    Stevan White
    2012-03-27

    Added a couple of PDFs illustrating the problem with different builds of FreeSerif.

    Only the file deva-plain-deva-and-dev2.pdf contains correct rendering, in the section labelled "FreeSerif 'deva'"

    Notice the 'dev2' section in both PDFs has diagonal lines (viramas) beneath letters, which ought to have had the effect of transforming the letter, and in the dev2-only.pdf file, both sections show this problem.

    Furthermore, if you look carefully in the dev2-and-deva.pfd file, at the last word in the first line of the two sections,
    there is a letter consisting of a vertical line with a big right hook at top. It comes in the wrong order in the dev2 section. This is the vowel "i", which is supposed to undergo a re-ordering by the Indic shaping engine. This means the Indic shaping engine isn't functioning at all for 'dev2'.

    (The third run of text in the two files is Lohit Hindi, -- which has no Latin range -- )

    I should also add: Support for 'dev2' is very poor in Linux at this time, although Windows and Mac already use it heavily, and modern fonts are being produced using 'dev2' only.

     
  • Stevan White
    Stevan White
    2012-03-28

    I had found that LibreOffice behaves very differently with respect to TrueType or OpenType tables.
    https://bugs.freedesktop.org/show_bug.cgi?id=47995

    So I repeated the tests on TrueType files.
    But evidently it's not the same thing as in LibreOffice: the results for TrueType are identical to OpenType for the XeTeX test.

     
  • Khaled Hosny
    Khaled Hosny
    2012-11-26

    We are switching XeTeX to use HarfBuzz for OpenType shaping (already done in master), since I don’t know much Indic, I’m attaching the result of the test file on my machine using Free Serif 0412.2263 and Lohit Hindi 2.4.3 (probably I should use the latest versions).

     
    Attachments
  • Khaled Hosny
    Khaled Hosny
    2012-11-26

    • Description has changed:

    Diff:

    --- old
    +++ new
    @@ -1,5 +1,5 @@
     Looks like XeTeX really has no functioning support for the 2005 v.2 Indic script tags.
    -\(This was discovered in bug 3511113\)
    +(This was discovered in bug 3511113)
    
     I've particularly investigated the Devanagari ones.
    
    @@ -7,16 +7,17 @@
     deva: http://www.microsoft.com/typography/OpenType%20Dev/devanagari/introO.mspx
    
     dev2 adds
    -\* locl  Localized form substitution
    -\* rkrf   Rakaar form substitution   \*NOTE a typo has 'pref' instead of 'rkrf'
    -\* cjct  Conjunct form substitution
    -\* calt  Contextual alternates 
    -\* kern  Kerning
    
    -Also, in dev2, 'dist' is applied \*after\* 'abvm' and 'blwm'.
    +* locl  Localized form substitution
    +* rkrf   Rakaar form substitution   *NOTE a typo has 'pref' instead of 'rkrf'*
    +* cjct  Conjunct form substitution
    +* calt  Contextual alternates 
    +* kern  Kerning
    +
    +Also, in dev2, 'dist' is applied *after* 'abvm' and 'blwm'.
    
     Questions had arisen regarding a font that had specifications set to be activated
    -for either 'dev2' or 'deva'.  I removed all the specifications of 'deva', and ran a test \(attached\)
    +for either 'dev2' or 'deva'.  I removed all the specifications of 'deva', and ran a test (attached)
     which specified runs of script 'deva' and 'dev2'.  Result: no lookups were activated for either
     script tag.
    
    • status: open --> pending
    • assigned_to: Jonathan Kew --> Khaled Hosny
    • milestone: --> v0.9999
     
  • Khaled Hosny
    Khaled Hosny
    2013-03-11

    • Status: pending --> closed
     


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