The numbers for right-to-left scripts are processed also from right to
left, so the order of applying “numr” and “dnom” features should be
reversed in such case.
Fixes https://github.com/behdad/harfbuzz/issues/395
New approach to fix this:
69f9fbc420
Previous approach was reverted as it was too broad. See context:
https://github.com/behdad/harfbuzz/issues/347#issuecomment-267838368
With U+05E9,U+05B8,U+05C1,U+05DC and Arial Unicode, we now (correctly) disable
GDEF and GPOS, so we get results very close to Uniscribe, but slightly different
since our fallback position logic is not exactly the same:
Before: [gid1166=3+991|gid1142=0+737|gid5798=0+1434]
After: [gid1166=3+991|gid1142=0@402,-26+0|gid5798=0+1434]
Uniscribe: [gid1166=3+991|gid1142=0@348,0+0|gid5798=0+1434]
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.
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.
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
This was brorken earlier, though, it's really hard to notice it.
Unlike the glyph_h_origin(), an unset glyph_v_origin() does NOT
mean that the vertical origin is at 0,0.
Related to https://github.com/behdad/harfbuzz/issues/187
Separate the loops for the two cases of replacing with space
and deleting. For deleting, use the out-buffer machinery.
Needed for upcoming cluster merge fix.
The reason we turned it on is because Kazuraki uses it. But that's
not reason enough. Until the OpenType spec gets its act together re
adding design-direction to lookups, this is better user experience.
Previously, we expected users to provide BOT/EOT flags when the
text *segment* was at paragraph boundaries. This meant that for
clients that provide full paragraph to HarfBuzz (eg. Pango), they
had code like this:
hb_buffer_set_flags (hb_buffer,
(item_offset == 0 ? HB_BUFFER_FLAG_BOT : 0) |
(item_offset + item_length == paragraph_length ?
HB_BUFFER_FLAG_EOT : 0));
hb_buffer_add_utf8 (hb_buffer,
paragraph_text, paragraph_length,
item_offset, item_length);
After this change such clients can simply say:
hb_buffer_set_flags (hb_buffer,
HB_BUFFER_FLAG_BOT | HB_BUFFER_FLAG_EOT);
hb_buffer_add_utf8 (hb_buffer,
paragraph_text, paragraph_length,
item_offset, item_length);
Ie, HarfBuzz itself checks whether the segment is at the beginning/end
of the paragraph. Clients that only pass item-at-a-time to HarfBuzz
continue not setting any flags whatsoever.
Another way to put it is: if there's pre-context text in the buffer,
HarfBuzz ignores the BOT flag. If there's post-context, it ignores
EOT flag.
Originally we fixed those in 79d1007a50.
However, fonts like MongolianWhite don't have GDEF, but have IgnoreMarks
in their LigatureSubstitute init/etc features. We were synthesizing a
GDEF class of mark for Mongolian Variation Selectors and as such the
ligature lookups where not matching. Uniscribe doesn't do that.
I tried with more sophisticated fixes, like, if there is no GDEF and
a lookup-flag mismatch happens, instead of rejecting a match, try
skipping that glyph. That surely produces some interesting behavior,
but since we don't want to support fonts missing GDEF more than we have
to, I went for this simpler fix which is to always mark
default-ignorables as base when synthesizing GDEF.
Micro-test added.
Fixes rest of https://bugs.freedesktop.org/show_bug.cgi?id=65258
When seeing U+2044 FRACTION SLASH in the text, find decimal
digits (Unicode General Category Decimal_Number) around it,
and mark the pre-slash digits with 'numr' feature, the post-slash
digits with 'dnom' feature, and the whole sequence with 'frac'
feature.
This beautifully renders fractions with major Windows fonts,
and any other font that implements those features (numr/dnom is
enough for most fonts.)
Not the fastest way to do this, but good enough for a start.
This reverts commit d5bd0590ae.
The reasoning behind that logic was flawed and made under
a misunderstanding of the original problem, and caused
regressions as reported by Jonathan Kew in thread titled
"tibetan marks" in Oct 2013. Apparently I have had fixed
the original problem with this commit:
7e08f1258d
So, revert the faulty commit and everything seems to be in good
shape.
Before, if one called hb_shape() without setting script, language, and
direction on the buffer, hb_shape() was calling
hb_buffer_guess_segment_properties() on the user's behalf to guess
these.
This is very dangerous, since any serious user of HarfBuzz must set
these properly (specially important is direction). So now, we don't
guess properties by default. People not setting direction will get
an abort() now. If the old behavior is desired (fragile, good for
simple testing only), users can call
hb_buffer_guess_segment_properties() on the buffer just before calling
hb_shape().
This is a followup to 568000274c.
Looks like in the Latin shaper, Uniscribe zeroes all Unicode NSM
advances *after* GPOS, not before. Match that.
Can be tested using DejaVu Sans Mono, since that font has GPOS
rules to zero the mark advances on its own.
Before, we were zeroing advance width of attached marks for
non-Indic scripts, and not doing it for Indic.
We have now three different behaviors, which seem to better
reflect what Uniscribe is doing:
- For Indic, no explicit zeroing happens whatsoever, which
is the same as before,
- For Myanmar, zero advance width of glyphs marked as marks
*in GDEF*, and do that *before* applying GPOS. This seems
to be what the new Win8 Myanmar shaper does,
- For everything else, zero advance width of glyphs that are
from General_Category=Mn Unicode characters, and do so
before applying GPOS. This seems to be what Uniscribe does
for Latin at least.
With these changes, positioning of all tests matches for Myanmar,
except for the glitch in Uniscribe not applying 'mark'. See preivous
commit.
ebraminio
Behdad Esfahbod
Khaled Hosny
ThePhD
Sascha Brawer
Jonathan Kew