Fallback for Sinhala Consonant Clusters

[Martin J. Dürst via Unicode]

Hello Richard,

On 2018/10/14 09:02, Richard Wordingham via Unicode wrote:
> Are there fallback rules for Sinhala consonant clusters?  There are
> fallback rules for Devanagari, but I'm not sure if they read across.
> 
> The problem I am seeing is that the Pali syllable 'ndhe' න්‍ධෙ <U+0DB1
> NAYANNA, U+0DCA AL-LAKUNA, 200D ZWJ, U+0DB0 MAHAPRAANA DAYANNA, U+0DD9
> KOMBUVA>

Let's label this as (1)

> is being rendered identically to a hypothetical Sinhalese
> 'nēdha' නේධ <U+0DB1, U+0DDA DIGA KOMBUVA, U+0DB0>,

It (2) doesn't look identically to (1) here (Thunderbird on Win 8.1).

Your mail is written as if you are speaking about a general phenomenon, 
but I guess there are differences depending on the font and rendering stack.

> which in NFD is
> <U+0DB1, U+0DD9, U+0DCA, U+0DB0>, when I use a font that lacks the
> conjunct.  (Most fonts lack the conjunct.)  The Devanagari rules and my
> preference would lead to a fallback rendering as න්ධෙ  (Sinhalese
> 'ndhe'),

Here, this (3) looks like it has the same three components as (2), but 
the first two are exchanged, so that the piece that looks like @ is now 
in the middle (it was at the left in (1) and (2)).

Hope this helps.  Regards,    Martin.

> which is encoded as <U+0DB1 NAYANNA, U+0DCA AL-LAKUNA, U+0DB0
> MAHAPRAANA DAYANNA, U+0DD9 KOMBUVA>.  Is the rendering I am getting
> technically wrong, or is it merely undesirable?
> 
> The ambiguity arises in part because, like the Brahmi script, the
> Sinhala script uses its virama character as a vowel length indicator.
> 
> Missing touching consonants are being rendered almost as though there
> were no ZWJ, but the combination of consonant and al-lakuna is being
> rendered badly.
> 
> Richard.
> 
> .
> 

-- 
Prof. Dr.sc. Martin J. Dürst
Department of Intelligent Information Technology
College of Science and Engineering
Aoyama Gakuin University
Fuchinobe 5-1-10, Chuo-ku, Sagamihara
252-5258 Japan