[Bug 825115] New: [kn_IN] Lohit Kannada glyphs of consonants with vowel signs -II, -EE, -OO and -AI should be optimized

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=825115

            Bug ID: 825115
        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] Lohit Kannada glyphs of consonants with vowel
                    signs -II, -EE, -OO and -AI should be optimized
        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

Description of problem:

Currently the Lohit Kannada fonts unnecessarily contain separate glyphs for
consonants with vowel signs -II, -EE, -OO and -AI. These are merely sequences
of other glyphs.

In the case of -II, -EE, -OO the glyphs are the same as those of the
corresponding short vowels plus a separate glyph 0CD5 Kannada Length Mark ೕ
(unlike in Telugu where the length mark ligates with the syllable). Therefore
instead of doing substitutions of:

CONSONANT + VOWEL_SIGN_II/EE/OO --> CONSONANT_VOWELSIGN_II/EE/OO

the optimized way would be to do:

CONSONANT + VOWEL_SIGN_II/EE/OO --> CONSONANT_VOWELSIGN_I/E/O LENGTH_MARK

If this is done, any changes that are reflected on the
CONSONANT_VOWELSIGN_I/E/O glyphs would automatically reflect for the long
vowels as well without additional work being needed. For instance, see my
recent report of bug 825104. If that bug is fixed for short vowels I, E and O,
automatically it would reflect for II, EE and OO also.

As for -AI, it is merely sequence of glyph for -E plus 0CD6 Kannada AI Length
Mark ೖ. So instead of doing substitutions of:

CONSONANT + VOWEL_SIGN_AI --> CONSONANT_VOWELSIGN_AI

the optimized way would be to do:

CONSONANT + VOWEL_SIGN_AI --> CONSONANT_VOWELSIGN_E AI_LENGTH_MARK

with same benefits as above.

Further, when handling combinations of:

CONSONANT1 + VIRAMA + CONSONANT2 + VOWEL_SIGN_II/EE/OO/AU

by separating the length mark as recommended here, the sub-base form of
CONSONANT2 can be placed closer to the base CONSONANT1 which is also
typographically a desirable factor in a good font. The rules would be:

CONSONANT1 + VIRAMA + CONSONANT2 + VOWEL_SIGN_II/EE/OO/AU -->
CONSONANT1_VOWEL_SIGN_I/E/O + SUB_BASE_CONSONANT_2 + (AI_)LENGTH_MARK

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

2.5.1

How reproducible:

Examine the internals of Lohit Kannada font.

Actual results:

Currently there are separate glyphs for consonants with vowel signs -II, -EE,
-OO and -AI unnecessarily. These are merely sequences of other glyphs.
Therefore any change effected on the component glyphs has to be re-done here.

Expected results:

The superfluous glyphs should be removed and the appropriate effect should be
achieved by appropriate smartfont rules as indicated above.

Additional info:

This would also reduce the size of the font. Not an issue on laptops/desktops
but nowadays Lohit fonts are finding their way into smaller screens such as
smartphones, and it would be good to have a trim font with small footprint.

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