Does not provide Uniscribe-compatible results, but should at least avoid
breaking hb-view due to out-of-order cluster values.
For RTL runs, ensure cluster values are non-increasing (instead of
non-decreasing).
Backporting from upstream:
commit b847f24ce855d24f6822bcd9c0006905e81b94d8
Author: Behdad Esfahbod <behdad@behdad.org>
Date: Wed Jul 25 19:29:16 2012 -0400
[arabic] Fix Arabic cursive positioning
This was clearly broken in testing. Who knows... Fixes for me.
Test with a Nastaleeq font, or with Arabic Typesetting.
Backporting from Chromium.
This was broken as a result of 7b84c536c1.
As Khaled reported, MarkMark positioning was broken with glyphs
resulting from a MultipleSubst. Fixed. Test with the ALLAH character
in Amiri.
Does not attempt to handle clusters in a Uniscribe- or HarfBuzz-compatible way;
just returns the original string indexes that CT maintains. These may even be
out-of-order in the case of reordrant glyphs.
The font is forming a post-base consonant in some samples, and Uniscribe
positions top matra on the post-base. Do the same.
Gurmukhi failures down from 59 to 41 (0.0674242%).
Just put it before base, which is what's expected.
Malayalam failures down from 1559 to 1197 (0.114172%).
BENGALI: 353988 out of 354285 tests passed. 297 failed (0.0838308%)
DEVANAGARI: 693571 out of 693628 tests passed. 57 failed (0.00821766%)
GUJARATI: 366489 out of 366506 tests passed. 17 failed (0.0046384%)
GURMUKHI: 60750 out of 60809 tests passed. 59 failed (0.0970251%)
KANNADA: 950956 out of 951913 tests passed. 957 failed (0.100534%)
KHMER: 299094 out of 299124 tests passed. 30 failed (0.0100293%)
MALAYALAM: 1047219 out of 1048416 tests passed. 1197 failed (0.114172%)
ORIYA: 42320 out of 42329 tests passed. 9 failed (0.021262%)
SINHALA: 271699 out of 271847 tests passed. 148 failed (0.0544424%)
TAMIL: 1091837 out of 1091837 tests passed. 0 failed (0%)
TELUGU: 970524 out of 970573 tests passed. 49 failed (0.00504856%)
The sequence Ra,H,Ya in Bengali is ambigious and Unicode encoded that to
get Ya-Phalaa, one would place ZWJ before Halant. Ie. a ZWJ,H sequence
requests subjoining, while a H,ZWJ requests Half form. Implement that.
Bengali failures go down from 377 to 297 (0.0838308%).
Gujarati is down by 4 to 17 (0.0046384%).
Kannada is down by 226 to 957 (0.100534%).
Current status:
BENGALI: 353988 out of 354285 tests passed. 297 failed (0.0838308%)
DEVANAGARI: 693571 out of 693628 tests passed. 57 failed (0.00821766%)
GUJARATI: 366489 out of 366506 tests passed. 17 failed (0.0046384%)
GURMUKHI: 60750 out of 60809 tests passed. 59 failed (0.0970251%)
KANNADA: 950956 out of 951913 tests passed. 957 failed (0.100534%)
KHMER: 299094 out of 299124 tests passed. 30 failed (0.0100293%)
MALAYALAM: 1046857 out of 1048416 tests passed. 1559 failed (0.148701%)
ORIYA: 42320 out of 42329 tests passed. 9 failed (0.021262%)
SINHALA: 271699 out of 271847 tests passed. 148 failed (0.0544424%)
TAMIL: 1091837 out of 1091837 tests passed. 0 failed (0%)
TELUGU: 970524 out of 970573 tests passed. 49 failed (0.00504856%)
Also limit joiners.
This limits our syllable length to a constant, and is
closer to what Uniscribe does anyway.
Two Devanagari tests regressed, but who cares about tests with 20
joiners in a row?! Devanagari at 57 (0.00821766%) now.
In Khmer coeng model, a V,Ra can go *after* matras. If it goes after a
split matra, it should be reordered to *before* the left part of such matra.
Khmer failures down from 136 to 39 (0.0130381%).
Apparently if there is C,V,ZWJ,C, the first C will be base, but if
it's C,ZWJ,V,C, the second one will be.
Note that Uniscribe implements this differently, by breaking syllable in
the case of C,ZWJ,V,C and putting the first consonant in one syllable
and the rest in the next syllable.
Sinhala failures down from 208 to 158 (0.0581209%). No changes to
Khmer.
Sinhala does not have half forms. And most (all?) consonants can be
base, except when preceded by ZWJ, which would request a subjoined form.
Hence switch the base algorithm to categorize with Khmer, start search
at start, and stop at a ZWJ.
Also, mark all pos=base consonants after base to be subjoined. Mark
base itself to have pos=base.
Finally, adjust Sinhala's reph position to after-main.
Brings down Sinhala failures from 455 to 328 (0.120656%).
If, say, a H,ZWJ,C ligature was formed, we don't want the code to detec
that as a Halant. So, ignore ligatures when matching category in
final_reordering.
Sinhala failures down from 514 to 455 (0.167374%).
Seems to be about what Uniscribe does. Not exactly. But close enough.
More consonants will start a new cluster.
A few scripts went way down in failures. In particular:
- Devanagari failures went down from 490 to 56.
- Telugu went down from 113 to 49.
Other scripts went down slightly or didn't change. New numbers:
BENGALI: 353908 out of 354285 tests passed. 377 failed (0.106412%)
DEVANAGARI: 693572 out of 693628 tests passed. 56 failed (0.00807349%)
GUJARATI: 366485 out of 366506 tests passed. 21 failed (0.00572978%)
GURMUKHI: 60750 out of 60809 tests passed. 59 failed (0.0970251%)
KANNADA: 950730 out of 951913 tests passed. 1183 failed (0.124276%)
KHMER: 298613 out of 299124 tests passed. 511 failed (0.170832%)
MALAYALAM: 1046881 out of 1048416 tests passed. 1535 failed (0.146411%)
ORIYA: 42320 out of 42329 tests passed. 9 failed (0.021262%)
SINHALA: 271333 out of 271847 tests passed. 514 failed (0.189077%)
TAMIL: 1091837 out of 1091837 tests passed. 0 failed (0%)
TELUGU: 970524 out of 970573 tests passed. 49 failed (0.00504856%)
Some of the remaining Telugu and Devanagari issues seem to be Uniscribe
eating Anusvara when placed before a non-joiner. Ouch!
Uniscribe reorders U+0E3A to be after U+0E38 and U+0E39. We do that by
modifying the ccc for U+0E3A.
Fixes the two remaining Thai failures (see previous commit).
Adjust the list of marks before SARA AM that get the reordering
treatment. Also adjust cluster formation to match Uniscribe.
With Wikipedia test data, now I see:
- For Thai, with the Angsana New font from Win7, I see 54 failures out
of over 4M tests (0.00129107%). Of the 54, two are legitimate
reordering issues (fix coming soon), and the other 52 are simply
Uniscribe using a zero-width space char instead of an unknown
character for missing glyphs. No idea why. The missing-glyph
sequences include one that is a Thai character followed by an Arabic
Sokun. Someone confused it with Nikhahit I assume!
- For Lao, with the Dokchampa font from Win7, 33 tests fail out of
54k (0.0615167%). All seem to be insignificant mark positioning
with two marks on a base. Have to investigate.
Althought IndicMatraCategory.txt classifies it as Top_And_Right matra,
it does not have Unicode decomposition, and Uniscribe does not do
anything special about it either.
Gujarati failures down from 0.672% to 0.0130966%.
That's really what Uniscribe does, and explains a lot of pecularities of
Halant,ZWNJ before the base.
Sent Telugu from 1% failures to 0.03%. Improved Kannada and Malayalam
slightly. Fixed half of Bengali, and did NOT break anything!
Following what the spec says.
Brings down Telugu failures from 40% to 3.75%, and Kannada failures from
44% to 10%. Does NOT affect other scripts' test results.
This is a hack for now. Will be fixed when we do complex-shaper-driven
normalization properly.
The results with or without decomposition are the same, but Uniscribe
does not normalize, so this matches better.
In Sinhala, Rakar is formed by Al-Lakuna,ZWJ,Ra. If you put that at the
end of a Consonant,Matra syllable, you get a dotted-circle from
Uniscribe. Apparently adding a ZWJ before the Al-Lakuna "fixes" that.
And people have been encoding that sequence... So, allow a forced
"ZWJ,Virama,ZWJ,Ra" sequence at the of syllables.
Fixes some 100 or more of Sinhala failures. Now at 622 only (0.23%).
POS_BASE can disappear if base ligated backward. Define base as last
with position not after base.
Fixes a few hundred of Sinhala failures with Iskoola Pota.
It's a visual Repha.
Still not positioning logical Repha as occurs in Malayalam.
Another 200 Khmer failures fixed. 547 to go. That's better than
Devanagari!
This reorders glyphs within the cluster to a nominal order. This should
have no visible effect on the output, but helps with testing, for
getting the same hb-shape output for visually-equal glyphs for each
cluster.
In such scripts (ie. Khmer), a ZWJ/ZWNJ shouldn't stop the search for
base. So, instead just choose the first consonant as base directly.
Test sequence:
U+1798,200c,U+17C9,U+17D2,U+179B,U+17C1,U+17C7
Mark stuff after a pre-base reordering Ro 'cfar'. Used in Khmer.
This allows distinguishing the following cases with MS Khmer fonts:
U+1784,U+17D2,U+179A,U+17D2,U+1782
U+1784,U+17D2,U+1782,U+17D2,U+179A
In Khmer, a final subjoined consonant or independent vowel can occur
after matras. This final subjoined thing should NOT be reordered to
before the matra even though it's subjoined.
Fixes another 1k of the Khmer failures. Not much left really.
Amend the syllable structure to allow a final subscripted consonant
(Coeng+C) and a final subscripted independent vowel (Coeng+V).
Fixes another 2k of Khmer failures.
Normally, we attach the Halant to the previous character and move it
with it. For after-base consonants however, the Halant "belongs" to the
consonant after, so attach it so.
This fixes Bengali sequences involving post-base consonant Ya, which
should ligate with the Halant to form Ya Phala, but previously a
reordered matras was blocking the ligation.
Seems like this is what Uniscribe is doing, and does not break any fonts
we tested (with Devanagari, Malayalam, Khmer, and Bengali), while fixing
some Ra Phala sequences for Bengali with Vrinda. Fixes another 2% of
Bengali failures (a couple more to go).
Uniscribe does not apply 'kern' in the Indic module. Some of the Khmer
fonts they ship have small adjustments in the 'kern' table. Disable
'kern' in the Indic module under Uniscribe bug compatibility mode.
Fixes some 10% of the Khmer failures. Remains under 3% (excluding
dotted-circle ones).
Mark them the same as the Register Shifters for now. Need to rename
that category to something more sensible after all is settled.
Fixes another percent of Khmer failures. Down to under 3%!
We are going to split matras without a Unicode decompositions in a way
that the second half takes the codepoint of the whole matra. So,
position them where the second half is supposed to end up.
Since we use the OpenType versions of Uniscribe functions, we are
relying on that version of the WINNT API. Otherwise, usp10.h will hide
those symbols.
Previously was failing to match fonts that didn't support CHARSET_ANSI.
There still remains a problem with the Uniscribe backend, in that if a
font with the same family name is installed, and is newer, the native
one is preferred over the font we provide. Fixing it requires rewriting
the name table with a unique family name...
This was causing all object types to be non-POD and have static
initializers. We don't need that!
Now, most nil objects just moved from .bss to .data. Fixing for that
coming soon.
Behdad Esfahbod
Jonathan Kew