Fallback for Sinhala Consonant Clusters

Harshula via Unicode unicode at unicode.org
Tue Oct 16 06:00:18 CDT 2018

Hi Richard,

On 16/10/18 2:29 pm, Richard Wordingham via Unicode wrote:
> On Tue, 16 Oct 2018 11:59:54 +1100
> Harshula via Unicode <unicode at unicode.org> wrote:
>> Hi Richard,
>> On 16/10/18 6:57 am, Richard Wordingham via Unicode wrote:
>>> On Tue, 16 Oct 2018 02:47:36 +1100
>>> Harshula via Unicode <unicode at unicode.org> wrote:
>>>> Note, touching letters are formed by <ZWJ><AL-LAKUNA>, so they
>>>> should not be displayed as a fallback for <AL-LAKUNA><ZWJ>
>>>> conjuncts.  
>>> I don't follow that.  While the conjuncts with r-, -r and -y are
>>> very different to pairs of touching letters, the conjuncts for tth,
>>> nd, ndr, ndh, kv and tv would be very similar to the hypothetical
>>> corresponding touching letters and quite different to the fallbacks
>>> with visible al-lakuna.  
>> If you haven't already, it's best you read SLS 1134:2011:
>> http://www.language.lk/en/download/standards/
>> or the older SLS 1134:2004:
>> http://unicode.org/wg2/docs/n2737.pdf
> The latter actually says, in Section 5.8, that <AL-LAKUNA, ZWJ> may be
> used for either!  I suspect that that is a printing error.

The former (SLS1134:2011) has a section for Touching letters. It is
explicitly stated to use <ZWJ><AL-LAKUNA> for Touching letters.

Sorry, the file n2737.pdf hosted on unicode.org appears to be a draft.
It is not the final SLS1134:2004. The final contains a section on
Touching letters like SLS1134:2011.

> The Sri Lankan standard simply assumes that the rendering system can
> accommodate what is requested in the backing store.  It says nothing
> about fallbacks.  So, if the user specifies the the syllable ddho
> written with a conjunct and encoded as ද්‍ධො but the conjunct is
> missing from the fonts' repertoires, why is it right to display it with
> al-lakuna as though it were ද්ධො but wrong to display it with the
> touching letters encoded as ද‍්ධො?   There are three different
> correct ways of writing 'ddho', but many systems only support one of
> them (and some weirdly use a fourth method). 

When a font is missing a glyph during an *explicit* conjunct lookup, it
appears the most accurate solution is to display the missing glyph symbol.


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