[Libreoffice-bugs] [Bug 40319] New: Tamil grapheme clusters

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=40319

           Summary: Tamil grapheme clusters
           Product: LibreOffice
           Version: unspecified
          Platform: Other
        OS/Version: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: medium
         Component: Libreoffice
        AssignedTo: libreoffice-bugs at lists.freedesktop.org
        ReportedBy: samjnaa at gmail.com


For information in relation to bug 40292:

The following individual characters are considered independent grapheme
clusters in Tamil and hence should allow cursor placement immediately before
and after them:

INDEPENDENT_VOWEL
CONSONANT
TAMIL AYTAM (VISARGA)

The following character sequences are considered independent grapheme clusters
in Tamil and hence should allow cursor placement immediately before and after
them but not in between:

CONSONANT + VOWEL_SIGN
CONSONANT + VIRAMA

If a font provides the K.SSA ligature for KA + VIRAMA + SSA, then CONSONANT +
VIRAMA here, i.e. KA + VIRAMA on its own is *not* a grapheme cluster. In such a
case, the following character sequences are considered independent grapheme
clusters and hence should allow cursor placement immediately before and after
them but not in between, *despite* the above rule about CONSONANT + VIRAMA:

KA + VIRAMA + SSA
KA + VIRAMA + SSA + VOWEL_SIGN
KA + VIRAMA + SSA + VIRAMA

If a font *does not provide* a K.SSA ligature, and KA + VIRAMA + SSA is
displayed as KA with an overt virama followed by SSA, then the previous rule
should apply. (I'm not sure whether you will be able to alter the cursor
placement rule based on whether the font provides a ligature or not, but I am
giving the native users' perception. Cater to it as best as you can.)

The so called TAMIL ANUSVARA is a wrongly encoded character as it is never used
and never will be used in Tamil Unicode. Anyhow, as it is a combining mark, one
does not expect to place a cursor between it and its base. The general rule is
that no cursor placement is allowed in between a combining mark and its base.

Please ask if you wish to have more feedback or clarification.

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