Adobe World Ready Composer and ೊ
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Hi James,
Let me know if I understand you correctly. I assume you have a non-unicode glyph 'knDO' in your font that you want to activate when the input sequence is 'knDa' + 'knVowelO'. I would suggest you use the 'post' (Post-Base Substitutions) feature and simply substitute:feature post { sub knDa knVowelO by knDO; } post ;
From Microsoft's 'latest' spec (http://www.microsoft.com/typography/OpenTypeDev/kannada/intro.htm#features):Such substitutions can be used to create [...] post-base matra ligatures.
What you describe as InDesign's output is indeed the correct shaping behavior, except it isn't giving you ದೆ + ೂ but really ದ + ೊ (this obviously depends on the input character sequence). You can test this by copy/pasting the cluster into Richard Ishida's useful UniView web tool (http://r12a.github.io/uniview/). Paste into the 'Edit Buffer' field and click on the downward facing arrow.
I hope what I'm saying makes sense
Edit: Spelling and case.0 -
James Puckett said:Is this normal behavior for a Kannada shaping engine?It seem like it.
This will not work (at leat not in Indesign) as the knVowelO is not there any more at this point.feature post {
sub knDa knVowelO by knDO;
} post ;
You have to to do it like this:sub da_eMatra-kannada uuMatra-kannada by da_oMatra-kannada;
(sorry, I don't know the proper names in your naming but you should get the point)
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You can test this by copy/pasting the cluster into Richard Ishida's useful UniView web tool (http://r12a.github.io/uniview/). Paste into the 'Edit Buffer' field and click on the downward facing arrow.
Thanks for that! It’s a useful tool.
I figured it out from looking at ITF’s template code. The code that gets my stuff working is:feature post { sub knDa knVowelO by knDO; } post ;
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Hi Georg!
[...] knVowelO is not there any more at this point.
I don't understand what you mean here. The 'knVowelO' (Kannada Vowel Sign O 0CCA) is a an encoded character, and thus can be combined with a preceding base consonant to access a consonant-vowel mark ligature glyph using the 'post' feature.
Unrelated: Are you working on a Glyphs version for the iPad Pro?
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The 'knVowelO' (Kannada Vowel Sign O 0CCA) is a an encoded character, and thus can be combined with a preceding base consonant to access a consonant-vowel mark ligature glyph using the 'post' [sic] feature.
U+0CCA has a canonical decomposition to 0CC6 + 0CC2. As with other two-part vowel signs in Unicode, you can expect the layout engine to decompose at the character level, long before one gets to the glyph processing of features such as 'psts'* (which is processed relatively late in the shaping, after reordering).
* NB, the Post Base Substitutions feature tag is 'psts', not 'post'.
As the current Kannada specification** notes:4. Uniscribe splits two- or three-part matras into their parts. This splitting is a character-to-character operation.
So Georg is almost right to say that by the time the 'psts' feature is processed the Kannada vowel sign O glyph is no longer in the glyph stream: in fact, it was never there at all because the character has been decomposed even before the layout engine gets the glyphs from the cmap table.
** Note that Adobe's World Ready Composer implements the old XP 'knda' shaping model, not the current 'knd2' shaping. The older specifications are no longer available on the MS site, but I don't recall the behaviour differing with regard to two-part vowel signs.
In my Kannada fonts, I have typically already performed the substitutionkDa kSignE -> kDe
early in the 'psts' lookups; so then perform the substitutionkDe kSignUu -> kDo
Of course, you could do it various other ways, e.g. performingkDa kSignE kSignUu -> kDo
before performingkDa kSignE -> kDe
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PS. I encourage you to use a Uniscribe environment, rather than Adobe's WRC, as a core test environment, even for 'knda' (even if this means making a font with only 'knda' script tag support to force use of the old shaping model in a post-XP version of Windows). Over the years, I've seen small inconsistencies between Adobe's Indic implementations and that in Uniscribe (and Harfbuzz).
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That means testing in Firefox?0
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Firefox uses HarfBuzz, and though it strives to be Uniscribe-compatabile, if you really want to test against Uniscribe then IE (or Edge) would be a better choice (or pretty much any other MS product on Windows, for that matter).
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or pretty much any other MS product on Windows, for that matter
Keeping in mind that some Microsoft products may use different versions of Uniscribe. Office still, so far as I know, ships with its own version, which may differ from that which comes with Windows (this allows for compatibility within a given version of Office apps, regardless of which version of the OS they are running on).
To test the OS version of Uniscribe, I use Wordpad most of the time, but if I want to be sure to avoid anything coming between the font and OTLS — e.g. RichEdit — than I use NotePad.
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