Kannada JIHVAMULIYA and UPADHMANIYA insert dotted circles

[roozbehp]

According to Unicode, these should display fine just appearing by themselves. But HarfBuzz inserts dotted circles after them. Here's the result of:

./test/shaping/hb-unicode-encode 0CF1 20 0CF2| ./util/hb-view --font-file=$HOME/src/noto-fonts/unhinted/NotoSansKannada-Regular.ttf --output-file=kannada.png

[jfkthame]

The same will presumably apply to the equivalent Brahmi signs U+11003 and U+11004, as these also have Indic_Syllabic_Category=Consonant_With_Stacker, which is not being handled correctly by harfbuzz. (See hb-ot-shape-complex-indic-private.hh, which treats it as OT_Repha, with a suspicious-looking TODO comment!)

[jfkthame]

BTW, does the Noto Kannada font have any support for these characters (besides just rendering simple glyphs)? From a quick look, I'm not seeing any sign of the expected ligatures for things like <U+0CF2, U+0CAB>.

[behdad]

From shaping point of view looks to me like just treating them as consonant is best. I'll commit that for now.

[roozbehp]

@jfkthame There's a bug open for complex behavior of these in Noto Sans Kannada at https://github.com/googlei18n/noto-fonts/issues/459

[dscorbett]

This change breaks the latest development version of FreeSerif. FreeSerif uses 'psts' to substitute consonants with their subjoined forms following jihvamuliya and upadhmaniya, but now that Consonant_With_Stacker is treated as Consonant, 'psts' does not get applied.

[behdad]

This change breaks the latest development version of FreeSerif.

Humm....

FreeSerif uses 'psts' to substitute consonants with their subjoined forms

That should happen in 'pstf', not 'psts'.

following jihvamuliya and upadhmaniya, but now that Consonant_With_Stacker is treated as Consonant, 'psts' does not get applied.

[dscorbett]

'pstf' applies to “Halant + Consonant combinations”, but these characters subjoin following consonants without any halant. So is 'pstf' appropriate?

[behdad]

Why does 'psts' not apply?!

[behdad]

We apply 'psts' globally.

[dscorbett]

Is it global to the cluster or global to the whole input string?

[behdad]

Is it global to the cluster or global to the whole input string?

Global to the syllable. Though, backtrack/lookahead can span across syllable boundaries.

[behdad]

Ok so the problem I suppose is that now the stacked component ends up in a separate cluster...