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Fix text shaping of precomposed characters with HarfBuzz

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* src/hbfont.c (hbfont_shape): Fix setting TO of lglyph for
the case when Lisp shape-gstring function performed some
compositions by itself.  This happens with hebrew.el.  See
https://lists.freedesktop.org/archives/harfbuzz/2019-June/007396.html
for the details of the problem this solves.
This commit is contained in:
Eli Zaretskii 2019-06-13 11:49:30 +03:00
parent 4c3e78a9f4
commit 769e9fa5ae
1 changed files with 11 additions and 1 deletions
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12
src/hbfont.c
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@ -435,7 +435,17 @@ hbfont_shape (Lisp_Object lgstring, Lisp_Object direction)
/* All the glyphs in a cluster have the same values of FROM and TO. */
LGLYPH_SET_FROM (lglyph, from);
LGLYPH_SET_TO (lglyph, to);
/* This heuristic is for when the Lisp shape-gstring function
substitutes known precomposed characters for decomposed
sequences. E.g., hebrew.el does that. This makes TEXT_LEN
be smaller than the original length of the composed character
sequence. In that case, we must not alter the largest TO,
because the display engine must know that all the characters
in the original sequence were processed by the composition.
If we don't do this, some of the composed characters will be
displayed again as separate glyphs. */
if (!(to == text_len - 1 && LGLYPH_TO (lglyph) > to))
LGLYPH_SET_TO (lglyph, to);
/* Not every glyph in a cluster maps directly to a single
character; in general, N characters can yield M glyphs, where