Previously we only synthesized GDEF glyph classes if the glyphClassDef
array in GDEF was null. This worked well enough, and is indeed what
OpenType requires: "If the font does not include a GlyphClassDef table,
the client must define and maintain this information when using the
GSUB and GPOS tables." That sentence does not quite make sense since
one needs Unicode properties as well, but is close enough.
However, looks like Arial Unicode as shipped on WinXP, does have GDEF
glyph class array, but defines no classes for Hebrew. This results
in Hebrew marks not getting their widths zeroed. So, with this change,
we synthesize glyph class for any glyph that is not specified in the
GDEF glyph class table. Since, from our point of view, a glyph not
being listed in that table is a font bug, any unwanted consequence of
this change is a font bug :).
Note that we still don't get the same rendering as Uniscribe, since
Uniscribe seems to do fallback positioning as well, even though the
font does have a GPOS table (which does NOT cover Hebrew!). We are
not going to try to match that though.
Test string for Arial Unicode:
U+05E9,U+05B8,U+05C1,U+05DC
Before: [gid1166=3+991|gid1142=0+737|gid5798=0+1434]
After: [gid1166=3+991|gid1142=0+0|gid5798=0+1434]
Uniscribe: [gid1166=3+991|gid1142=0@348,0+0|gid5798=0+1434]
Note that our new output matches what we were generating until July
2014, because the Hebrew shaper used to zero mark advances based on
Unicode, NOT GDEF. That's 9e834e29e0.
Reported by Greg Douglas.
API changes:
- If NDEBUG is defined, define HB_NDEBUG
- Disable costlier sanity checks if HB_NDEBUG is defined.
In 1.2.3 introduced some code to disable costly sanity checks if
NDEBUG is defined. NDEBUG, however, disables all assert()s as
well. With HB_NDEBUG, one can disable costlier checks but keep
assert()s.
I'll probably add a way to define HB_NDEBUG automatically in
release tarballs. But for now, production systems that do NOT
define NDEBUG, are encouraged to define HB_NDEBUG for our build.
New API:
- hb_font_get_nominal_glyph_func_t
- hb_font_get_variation_glyph_func_t
- hb_font_funcs_set_nominal_glyph_func()
- hb_font_funcs_set_variation_glyph_func()
- hb_font_get_nominal_glyph()
- hb_font_get_variation_glyph()
Deprecated API:
- hb_font_get_glyph_func_t
- hb_font_funcs_set_glyph_func()
Clients that implement their own font-funcs are encouraged to replace
their get_glyph() implementation with a get_nominal_glyph() and
get_variation_glyph() pair. The variation version can assume that
variation_selector argument is not zero.
That commit moved the advance adjustment for mark positioning to
be applied immediately, instead of doing late before. This breaks
if mark advances are zeroed late, like in Arabic. Also, easier to
hit it in RTL scripts since a single mark with non-zero advance is
enough to hit the bug, whereas in LTR, at least two marks are needed.
This reopens https://github.com/behdad/harfbuzz/issues/211
The cursive+mark interaction is broken again. To be fixed in a
different way.
This better emulates Unicode grapheme clusters.
Note that Uniscribe does NOT do this, but should be harmless with most clients,
and improve fallback with clients that use HarfBuzz cluster as unit of fallback.
Fixes https://github.com/behdad/harfbuzz/issues/217
Fixes https://github.com/behdad/harfbuzz/issues/223
Right now we cannot test this because it has to be tested using hb-fuzzer.
We should move all fuzzing tests from test/shaping/tests/fuzzed.tests to
test/fuzzing/ and have its own test runner. At that point, should add
test from this issue as well.
This is what Microsoft's implementation does. Marks that need advance
need to add it back using 'dist' or other feature in GPOS. Update tests to
match.
Fixes https://github.com/behdad/harfbuzz/issues/211
What happens in that bug is that a mark is attached to base first,
then a second mark is cursive-chained to the first mark. This only
"works" because it's in the Indic shaper where mark advances are
not zeroed.
Before, we didn't allow cursive to run on marks at all. Fix that.
We also where updating mark major offsets at the end of GPOS, such
that changes in advance of base will not change the mark attachment
position. That was superior to the alternative (which is what Uniscribe
does BTW), but made it hard to apply cursive to the mark after it
was positioned. We could track major-direction offset changes and
apply that to cursive in the post process, but that's a much trickier
thing to do than the fix here, which is to immediately apply the
major-direction advance-width offsets... Ie.:
https://github.com/behdad/harfbuzz/issues/211#issuecomment-183194739
If this breaks any fonts, the font should be fixed to do mark attachment
after all the advances are set up first (kerning, etc).
Finally, this, still doesn't make us match Uniscribe, for I explained
in that bug. Looks like Uniscribe applies minor-direction cursive
adjustment immediate as well. We don't, and we like it our way, at
least for now. Eg. the sequence in the test case does this:
- The first subscript attaches with mark-to-base, moving in x only,
- The second subscript attaches with cursive attachment to first subscript
moving in x only,
- A final context rule moves the first subscript up by 104 units.
The way we do, the final shift-up, also shifts up the second subscript
mark because it's cursively-attached. Uniscribe doesn't. We get:
[ttaorya=0+1307|casubscriptorya=0@-242,104+-231|casubscriptnarroworya=0@20,104+507]
while Uniscribe gets:
[ttaorya=0+1307|casubscriptorya=0@-242,104+-211|casubscriptnarroworya=0+487]
note the different y-offset of the last glyph. In our view, after cursive,
things move together, period.
Behdad Esfahbod
Kal Conley
Konstantin Ritt