2011-07-21 06:51:18 +02:00
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/*
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* Copyright © 2011 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-private.hh"
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2011-07-21 21:25:01 +02:00
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#include "hb-ot-shape-complex-private.hh"
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2011-07-21 06:51:18 +02:00
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HB_BEGIN_DECLS
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2011-07-21 21:25:01 +02:00
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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. The shaper an either prefer decomposed (NFD) or
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* composed (NFC).
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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 desires,
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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, form 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 character but supports its decomposition,
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* well, use the decomposition.
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*
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* - The Indic shaper requests decomposed output. This will handle splitting
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* matra for the Indic shaper.
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*/
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2011-07-22 17:07:05 +02:00
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2011-07-21 17:31:08 +02:00
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static bool
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2011-07-22 17:07:05 +02:00
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decompose (hb_ot_shape_context_t *c,
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2011-07-22 22:15:32 +02:00
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bool shortest,
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2011-07-22 17:07:05 +02:00
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hb_codepoint_t ab)
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2011-07-21 06:51:18 +02:00
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{
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2011-07-22 17:07:05 +02:00
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hb_codepoint_t a, b, glyph;
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2011-07-22 22:15:32 +02:00
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if (!hb_unicode_decompose (c->buffer->unicode, ab, &a, &b) ||
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!hb_font_get_glyph (c->font, b, 0, &glyph))
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return FALSE;
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2011-07-22 17:07:05 +02:00
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2011-07-22 22:15:32 +02:00
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/* XXX handle singleton decompositions */
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bool has_a = hb_font_get_glyph (c->font, a, 0, &glyph);
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if (shortest && has_a) {
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/* Output a and b */
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c->buffer->output_glyph (a);
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c->buffer->output_glyph (b);
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return TRUE;
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}
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2011-07-21 06:51:18 +02:00
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2011-07-22 22:15:32 +02:00
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if (decompose (c, shortest, a)) {
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c->buffer->output_glyph (b);
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return TRUE;
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}
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2011-07-22 17:07:05 +02:00
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2011-07-22 22:15:32 +02:00
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if (has_a) {
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c->buffer->output_glyph (a);
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c->buffer->output_glyph (b);
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2011-07-22 17:07:05 +02:00
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return TRUE;
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}
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2011-07-22 22:15:32 +02:00
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return FALSE;
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2011-07-21 17:31:08 +02:00
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}
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2011-07-22 22:15:32 +02:00
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static void
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decompose_current_glyph (hb_ot_shape_context_t *c,
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bool shortest)
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2011-07-21 18:16:45 +02:00
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{
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2011-07-22 22:15:32 +02:00
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if (decompose (c, shortest, c->buffer->info[c->buffer->idx].codepoint))
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c->buffer->skip_glyph ();
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else
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c->buffer->next_glyph ();
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2011-07-21 18:16:45 +02:00
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}
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2011-07-22 17:07:05 +02:00
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static void
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2011-07-22 22:15:32 +02:00
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decompose_single_char_cluster (hb_ot_shape_context_t *c,
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bool will_recompose)
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2011-07-21 17:31:08 +02:00
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{
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2011-07-22 22:15:32 +02:00
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hb_codepoint_t glyph;
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/* If recomposing and font supports this, we're good to go */
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if (will_recompose && hb_font_get_glyph (c->font, c->buffer->info[c->buffer->idx].codepoint, 0, &glyph)) {
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c->buffer->next_glyph ();
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return;
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}
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decompose_current_glyph (c, will_recompose);
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2011-07-21 06:51:18 +02:00
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}
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2011-07-22 17:07:05 +02:00
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static void
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2011-07-22 22:15:32 +02:00
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decompose_multi_char_cluster (hb_ot_shape_context_t *c,
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unsigned int end)
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2011-07-21 06:51:18 +02:00
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{
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2011-07-21 21:25:01 +02:00
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/* TODO Currently if there's a variation-selector we give-up, it's just too hard. */
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2011-07-22 22:15:32 +02:00
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for (unsigned int i = c->buffer->idx; i < end; i++)
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2011-07-21 18:16:45 +02:00
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if (unlikely (is_variation_selector (c->buffer->info[i].codepoint)))
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2011-07-22 17:07:05 +02:00
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return;
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2011-07-21 18:16:45 +02:00
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2011-07-22 22:15:32 +02:00
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while (c->buffer->idx < end)
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decompose_current_glyph (c, FALSE);
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2011-07-21 06:51:18 +02:00
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}
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2011-07-22 17:07:05 +02:00
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void
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2011-07-21 21:25:01 +02:00
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_hb_ot_shape_normalize (hb_ot_shape_context_t *c)
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2011-07-21 06:51:18 +02:00
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{
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hb_buffer_t *buffer = c->buffer;
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bool recompose = !hb_ot_shape_complex_prefer_decomposed (c->plan->shaper);
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2011-07-22 22:15:32 +02:00
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bool has_multichar_clusters = FALSE;
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2011-07-21 21:25:01 +02:00
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buffer->clear_output ();
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2011-07-22 22:15:32 +02:00
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/* First round, decompose */
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2011-07-21 21:25:01 +02:00
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unsigned int count = buffer->len;
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2011-07-22 17:28:07 +02:00
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for (buffer->idx = 0; buffer->idx < count;)
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2011-07-21 21:25:01 +02:00
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{
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unsigned int end;
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2011-07-22 17:28:07 +02:00
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for (end = buffer->idx + 1; end < count; end++)
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if (buffer->info[buffer->idx].cluster != buffer->info[end].cluster)
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break;
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2011-07-21 21:25:01 +02:00
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2011-07-22 17:28:07 +02:00
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if (buffer->idx + 1 == end)
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2011-07-22 22:15:32 +02:00
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decompose_single_char_cluster (c, recompose);
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else {
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decompose_multi_char_cluster (c, end);
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has_multichar_clusters = TRUE;
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}
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2011-07-21 06:51:18 +02:00
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}
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2011-07-22 17:28:07 +02:00
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buffer->swap_buffers ();
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2011-07-22 22:15:32 +02:00
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/* Technically speaking, two characters with ccc=0 may combine. But all
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* those cases are in languages that the indic module handles (which expects
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* decomposed), or in Hangul jamo, which again, we want decomposed anyway.
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* So we don't bother combining across cluster boundaries. */
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if (!has_multichar_clusters)
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return; /* Done! */
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/* Second round, reorder (inplace) */
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/* Third round, recompose */
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if (recompose) {
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}
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2011-07-21 06:51:18 +02:00
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}
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HB_END_DECLS
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