434 lines
14 KiB
C++
434 lines
14 KiB
C++
/*
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* Copyright © 2011,2012 Google, Inc.
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*
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* This is part of HarfBuzz, a text shaping library.
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*
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* Permission is hereby granted, without written agreement and without
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* license or royalty fees, to use, copy, modify, and distribute this
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* software and its documentation for any purpose, provided that the
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* above copyright notice and the following two paragraphs appear in
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* all copies of this software.
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*
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* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
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* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
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* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*
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* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
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* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
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* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*
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* Google Author(s): Behdad Esfahbod
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*/
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#include "hb-ot-shape-normalize.hh"
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#include "hb-ot-shape-complex.hh"
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#include "hb-ot-shape.hh"
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/*
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* HIGHLEVEL DESIGN:
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*
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* This file exports one main function: _hb_ot_shape_normalize().
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*
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* This function closely reflects the Unicode Normalization Algorithm,
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* yet it's different.
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*
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* Each shaper specifies whether it prefers decomposed (NFD) or composed (NFC).
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* The logic however tries to use whatever the font can support.
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*
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* In general what happens is that: each grapheme is decomposed in a chain
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* of 1:2 decompositions, marks reordered, and then recomposed if desired,
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* so far it's like Unicode Normalization. However, the decomposition and
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* recomposition only happens if the font supports the resulting characters.
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*
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* The goals are:
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*
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* - Try to render all canonically equivalent strings similarly. To really
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* achieve this we have to always do the full decomposition and then
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* selectively recompose from there. It's kinda too expensive though, so
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* we skip some cases. For example, if composed is desired, we simply
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* don't touch 1-character clusters that are supported by the font, even
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* though their NFC may be different.
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*
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* - When a font has a precomposed character for a sequence but the 'ccmp'
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* feature in the font is not adequate, use the precomposed character
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* which typically has better mark positioning.
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*
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* - When a font does not support a combining mark, but supports it precomposed
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* with previous base, use that. This needs the itemizer to have this
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* knowledge too. We need to provide assistance to the itemizer.
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*
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* - When a font does not support a character but supports its canonical
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* decomposition, well, use the decomposition.
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*
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* - The complex shapers can customize the compose and decompose functions to
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* offload some of their requirements to the normalizer. For example, the
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* Indic shaper may want to disallow recomposing of two matras.
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*/
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static bool
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decompose_unicode (const hb_ot_shape_normalize_context_t *c,
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hb_codepoint_t ab,
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hb_codepoint_t *a,
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hb_codepoint_t *b)
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{
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return (bool) c->unicode->decompose (ab, a, b);
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}
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static bool
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compose_unicode (const hb_ot_shape_normalize_context_t *c,
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hb_codepoint_t a,
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hb_codepoint_t b,
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hb_codepoint_t *ab)
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{
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return (bool) c->unicode->compose (a, b, ab);
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}
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static inline void
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set_glyph (hb_glyph_info_t &info, hb_font_t *font)
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{
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(void) font->get_nominal_glyph (info.codepoint, &info.glyph_index());
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}
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static inline void
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output_char (hb_buffer_t *buffer, hb_codepoint_t unichar, hb_codepoint_t glyph)
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{
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buffer->cur().glyph_index() = glyph;
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buffer->output_glyph (unichar); /* This is very confusing indeed. */
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_hb_glyph_info_set_unicode_props (&buffer->prev(), buffer);
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}
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static inline void
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next_char (hb_buffer_t *buffer, hb_codepoint_t glyph)
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{
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buffer->cur().glyph_index() = glyph;
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buffer->next_glyph ();
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}
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static inline void
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skip_char (hb_buffer_t *buffer)
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{
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buffer->skip_glyph ();
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}
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/* Returns 0 if didn't decompose, number of resulting characters otherwise. */
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static inline unsigned int
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decompose (const hb_ot_shape_normalize_context_t *c, bool shortest, hb_codepoint_t ab)
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{
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hb_codepoint_t a = 0, b = 0, a_glyph = 0, b_glyph = 0;
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hb_buffer_t * const buffer = c->buffer;
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hb_font_t * const font = c->font;
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if (!c->decompose (c, ab, &a, &b) ||
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(b && !font->get_nominal_glyph (b, &b_glyph)))
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return 0;
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bool has_a = (bool) font->get_nominal_glyph (a, &a_glyph);
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if (shortest && has_a) {
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/* Output a and b */
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output_char (buffer, a, a_glyph);
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if (likely (b)) {
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output_char (buffer, b, b_glyph);
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return 2;
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}
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return 1;
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}
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unsigned int ret;
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if ((ret = decompose (c, shortest, a))) {
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if (b) {
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output_char (buffer, b, b_glyph);
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return ret + 1;
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}
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return ret;
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}
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if (has_a) {
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output_char (buffer, a, a_glyph);
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if (likely (b)) {
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output_char (buffer, b, b_glyph);
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return 2;
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}
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return 1;
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}
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return 0;
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}
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static inline void
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decompose_current_character (const hb_ot_shape_normalize_context_t *c, bool shortest)
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{
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hb_buffer_t * const buffer = c->buffer;
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hb_codepoint_t u = buffer->cur().codepoint;
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hb_codepoint_t glyph = 0;
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if (shortest && c->font->get_nominal_glyph (u, &glyph))
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{
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next_char (buffer, glyph);
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return;
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}
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if (decompose (c, shortest, u))
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{
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skip_char (buffer);
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return;
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}
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if (!shortest && c->font->get_nominal_glyph (u, &glyph))
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{
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next_char (buffer, glyph);
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return;
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}
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if (_hb_glyph_info_is_unicode_space (&buffer->cur()))
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{
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hb_codepoint_t space_glyph;
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hb_unicode_funcs_t::space_t space_type = buffer->unicode->space_fallback_type (u);
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if (space_type != hb_unicode_funcs_t::NOT_SPACE && c->font->get_nominal_glyph (0x0020u, &space_glyph))
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{
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_hb_glyph_info_set_unicode_space_fallback_type (&buffer->cur(), space_type);
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next_char (buffer, space_glyph);
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buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_SPACE_FALLBACK;
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return;
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}
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}
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if (u == 0x2011u)
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{
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/* U+2011 is the only sensible character that is a no-break version of another character
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* and not a space. The space ones are handled already. Handle this lone one. */
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hb_codepoint_t other_glyph;
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if (c->font->get_nominal_glyph (0x2010u, &other_glyph))
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{
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next_char (buffer, other_glyph);
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return;
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}
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}
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next_char (buffer, glyph); /* glyph is initialized in earlier branches. */
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}
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static inline void
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handle_variation_selector_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool short_circuit)
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{
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/* TODO Currently if there's a variation-selector we give-up, it's just too hard. */
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hb_buffer_t * const buffer = c->buffer;
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hb_font_t * const font = c->font;
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for (; buffer->idx < end - 1 && buffer->successful;) {
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if (unlikely (buffer->unicode->is_variation_selector (buffer->cur(+1).codepoint))) {
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/* The next two lines are some ugly lines... But work. */
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if (font->get_variation_glyph (buffer->cur().codepoint, buffer->cur(+1).codepoint, &buffer->cur().glyph_index()))
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{
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buffer->replace_glyphs (2, 1, &buffer->cur().codepoint);
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}
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else
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{
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/* Just pass on the two characters separately, let GSUB do its magic. */
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set_glyph (buffer->cur(), font);
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buffer->next_glyph ();
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set_glyph (buffer->cur(), font);
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buffer->next_glyph ();
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}
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/* Skip any further variation selectors. */
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while (buffer->idx < end && unlikely (buffer->unicode->is_variation_selector (buffer->cur().codepoint)))
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{
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set_glyph (buffer->cur(), font);
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buffer->next_glyph ();
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}
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} else {
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set_glyph (buffer->cur(), font);
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buffer->next_glyph ();
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}
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}
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if (likely (buffer->idx < end)) {
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set_glyph (buffer->cur(), font);
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buffer->next_glyph ();
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}
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}
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static inline void
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decompose_multi_char_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool short_circuit)
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{
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hb_buffer_t * const buffer = c->buffer;
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for (unsigned int i = buffer->idx; i < end && buffer->successful; i++)
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if (unlikely (buffer->unicode->is_variation_selector (buffer->info[i].codepoint))) {
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handle_variation_selector_cluster (c, end, short_circuit);
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return;
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}
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while (buffer->idx < end && buffer->successful)
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decompose_current_character (c, short_circuit);
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}
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static inline void
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decompose_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool might_short_circuit, bool always_short_circuit)
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{
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if (likely (c->buffer->idx + 1 == end))
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decompose_current_character (c, might_short_circuit);
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else
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decompose_multi_char_cluster (c, end, always_short_circuit);
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}
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static int
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compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb)
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{
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unsigned int a = _hb_glyph_info_get_modified_combining_class (pa);
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unsigned int b = _hb_glyph_info_get_modified_combining_class (pb);
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return a < b ? -1 : a == b ? 0 : +1;
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}
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void
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_hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan,
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hb_buffer_t *buffer,
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hb_font_t *font)
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{
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if (unlikely (!buffer->len)) return;
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_hb_buffer_assert_unicode_vars (buffer);
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hb_ot_shape_normalization_mode_t mode = plan->shaper->normalization_preference;
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const hb_ot_shape_normalize_context_t c = {
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plan,
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buffer,
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font,
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buffer->unicode,
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plan->shaper->decompose ? plan->shaper->decompose : decompose_unicode,
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plan->shaper->compose ? plan->shaper->compose : compose_unicode
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};
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bool always_short_circuit = mode == HB_OT_SHAPE_NORMALIZATION_MODE_NONE;
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bool might_short_circuit = always_short_circuit ||
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(mode != HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED &&
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mode != HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT);
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unsigned int count;
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/* We do a fairly straightforward yet custom normalization process in three
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* separate rounds: decompose, reorder, recompose (if desired). Currently
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* this makes two buffer swaps. We can make it faster by moving the last
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* two rounds into the inner loop for the first round, but it's more readable
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* this way. */
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/* First round, decompose */
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buffer->clear_output ();
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count = buffer->len;
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for (buffer->idx = 0; buffer->idx < count && buffer->successful;)
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{
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unsigned int end;
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for (end = buffer->idx + 1; end < count; end++)
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if (likely (!HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->info[end]))))
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break;
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decompose_cluster (&c, end, might_short_circuit, always_short_circuit);
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}
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buffer->swap_buffers ();
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/* Second round, reorder (inplace) */
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count = buffer->len;
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for (unsigned int i = 0; i < count; i++)
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{
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if (_hb_glyph_info_get_modified_combining_class (&buffer->info[i]) == 0)
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continue;
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unsigned int end;
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for (end = i + 1; end < count; end++)
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if (_hb_glyph_info_get_modified_combining_class (&buffer->info[end]) == 0)
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break;
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/* We are going to do a O(n^2). Only do this if the sequence is short. */
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if (end - i > HB_OT_SHAPE_COMPLEX_MAX_COMBINING_MARKS) {
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i = end;
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continue;
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}
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buffer->sort (i, end, compare_combining_class);
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if (plan->shaper->reorder_marks)
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plan->shaper->reorder_marks (plan, buffer, i, end);
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i = end;
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}
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if (mode == HB_OT_SHAPE_NORMALIZATION_MODE_NONE ||
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mode == HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED)
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return;
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/* Third round, recompose */
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/* As noted in the comment earlier, we don't try to combine
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* ccc=0 chars with their previous Starter. */
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buffer->clear_output ();
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count = buffer->len;
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unsigned int starter = 0;
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buffer->next_glyph ();
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while (buffer->idx < count && buffer->successful)
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{
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hb_codepoint_t composed, glyph;
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if (/* We don't try to compose a non-mark character with it's preceding starter.
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* This is both an optimization to avoid trying to compose every two neighboring
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* glyphs in most scripts AND a desired feature for Hangul. Apparently Hangul
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* fonts are not designed to mix-and-match pre-composed syllables and Jamo. */
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HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->cur())))
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{
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if (/* If there's anything between the starter and this char, they should have CCC
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* smaller than this character's. */
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(starter == buffer->out_len - 1 ||
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info_cc (buffer->prev()) < info_cc (buffer->cur())) &&
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/* And compose. */
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c.compose (&c,
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buffer->out_info[starter].codepoint,
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buffer->cur().codepoint,
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&composed) &&
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/* And the font has glyph for the composite. */
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font->get_nominal_glyph (composed, &glyph))
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{
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/* Composes. */
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buffer->next_glyph (); /* Copy to out-buffer. */
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if (unlikely (!buffer->successful))
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return;
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buffer->merge_out_clusters (starter, buffer->out_len);
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buffer->out_len--; /* Remove the second composable. */
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/* Modify starter and carry on. */
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buffer->out_info[starter].codepoint = composed;
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buffer->out_info[starter].glyph_index() = glyph;
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_hb_glyph_info_set_unicode_props (&buffer->out_info[starter], buffer);
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continue;
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}
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}
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/* Blocked, or doesn't compose. */
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buffer->next_glyph ();
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if (info_cc (buffer->prev()) == 0)
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starter = buffer->out_len - 1;
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}
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buffer->swap_buffers ();
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if (buffer->scratch_flags & HB_BUFFER_SCRATCH_FLAG_HAS_CGJ)
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{
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/* For all CGJ, check if it prevented any reordering at all.
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* If it did NOT, then make it skippable.
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* https://github.com/harfbuzz/harfbuzz/issues/554
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*/
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for (unsigned int i = 1; i + 1 < buffer->len; i++)
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if (buffer->info[i].codepoint == 0x034Fu/*CGJ*/ &&
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info_cc(buffer->info[i-1]) <= info_cc(buffer->info[i+1]))
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{
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_hb_glyph_info_unhide (&buffer->info[i]);
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}
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}
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}
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