[Bug 827516] New: [kn_IN] Vowel Signs U and UU do not correctly attach to many consonants in Lohit Kannada

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=827516

            Bug ID: 827516
        QA Contact: extras-qa at fedoraproject.org
          Severity: unspecified
           Version: 16
          Priority: unspecified
                CC: fonts-bugs at lists.fedoraproject.org,
                    i18n-bugs at lists.fedoraproject.org, psatpute at redhat.com
          Assignee: psatpute at redhat.com
           Summary: [kn_IN] Vowel Signs U and UU do not correctly attach
                    to many consonants in Lohit Kannada
        Regression: ---
      Story Points: ---
    Classification: Fedora
                OS: Unspecified
          Reporter: samjnaa at gmail.com
              Type: Bug
     Documentation: ---
          Hardware: Unspecified
        Mount Type: ---
            Status: NEW
         Component: lohit-kannada-fonts
           Product: Fedora

Created attachment 588536
  --> https://bugzilla.redhat.com/attachment.cgi?id=588536&action=edit
ODT and PDF for test-case

Description of problem:

While most other CONSONANT + VOWEL SIGN combinations in Lohit Kannada are
mapped to precomposed glyphs, there are no pre-composed glyphs for vowel signs
U and UU except for the consonants PA, PHA and VA (where the stroke for U/UU
needs to come from below the consonant rather than the normal right side of the
consonant).

While in most cases, by virtue of appropriate RSB and LSB values of the
consonant glyph and vowel sign glyph, the simple sequence of the two glyphs
creates an appropriate appearance, this leaves out several instances where the
glyphs do not overlap at all and hence appear disjointed. For a professional
appearance of the font, this should be fixed.

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

2.5.1

How reproducible:

Input all possible sequences of Kannada consonants with vowel signs U and UU.
(See attached ODT for text. Use BabelMap
[http://www.babelstone.co.uk/software/babelmap.html] if you want the
codepoints.)

Actual results:

You can see (as in the attached PDF) that some consonants do not properly get
attached to the vowel signs U and UU.

Expected results:

All consonants should properly get attached to the vowel signs U and UU.

Additional info:

Consonants which are not properly joined with vowel sign U:

KA* NYA DDA DA BA RA SSA** RRA LLLA***

* = see at high magnification
** = may need separate precomposed glyph with some adjustment to shape of left
side of vowel sign
*** = so-called FA of Kannada Unicode

Consonants which are not properly joined with vowel sign UU:

Those already listed above for U, plus GHA and LLA, due to the shorter height
of the left-side ending node of this vowel sign.

I think in most cases appropriate kerning should solve the problem, except for
SSA + -U/-UU, GHA + -UU and LLA + -UU where separate glyphs would be advisable.

It is curious to note that DDA DA and BA are all disjointed whereas their
aspirated counterparts DDHA DHA and BHA which all have only an additional
notch-like stroke at the bottom are correctly joined with the vowel sign. I
think the LSB RSB values are carelessly allotted in some cases, unfortunately.

Other problems:

CU JU -- the pointed part on the left of the vowel sign U passes through the
consonants and comes out above (see carefully) -- actually *negative* kerning
is needed here so that the pointed part should only enter the consonant and not
again exit it. 

(It seems this problem does not occur for vowel sign UU due to the shorter
height of the left-side ending node of this vowel sign which causes a problem
with GHA and LLA instead -- see above!)

Note:

Unfortunately I will not be able to provide a TTF patch for this as I am
already short of time on my official projects. Please take care of it. Thank
you!

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