Edit
kc3-lang/harfbuzz/src/hb-ot-shape-normalize.cc
Behdad Esfahbod
- src/hb-ot-shape-normalize.cc
-
/* * Copyright © 2011 Google, Inc. * * This is part of HarfBuzz, a text shaping library. * * Permission is hereby granted, without written agreement and without * license or royalty fees, to use, copy, modify, and distribute this * software and its documentation for any purpose, provided that the * above copyright notice and the following two paragraphs appear in * all copies of this software. * * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH * DAMAGE. * * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND * FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. * * Google Author(s): Behdad Esfahbod */ #include "hb-ot-shape-private.hh" #include "hb-ot-shape-complex-private.hh" /* * HIGHLEVEL DESIGN: * * This file exports one main function: _hb_ot_shape_normalize(). * * This function closely reflects the Unicode Normalization Algorithm, * yet it's different. The shaper an either prefer decomposed (NFD) or * composed (NFC). * * In general what happens is that: each grapheme is decomposed in a chain * of 1:2 decompositions, marks reordered, and then recomposed if desires, * so far it's like Unicode Normalization. However, the decomposition and * recomposition only happens if the font supports the resulting characters. * * The goals are: * * - Try to render all canonically equivalent strings similarly. To really * achieve this we have to always do the full decomposition and then * selectively recompose from there. It's kinda too expensive though, so * we skip some cases. For example, if composed is desired, we simply * don't touch 1-character clusters that are supported by the font, even * though their NFC may be different. * * - When a font has a precomposed character for a sequence but the 'ccmp' * feature in the font is not adequate, form use the precomposed character * which typically has better mark positioning. * * - When a font does not support a character but supports its decomposition, * well, use the decomposition. * * - The Indic shaper requests decomposed output. This will handle splitting * matra for the Indic shaper. */ static void output_glyph (hb_ot_shape_context_t *c, hb_codepoint_t glyph) { hb_buffer_t *buffer = c->buffer; buffer->output_glyph (glyph); hb_glyph_info_set_unicode_props (&buffer->out_info[buffer->out_len - 1], buffer->unicode); } static bool decompose (hb_ot_shape_context_t *c, bool shortest, hb_codepoint_t ab) { hb_codepoint_t a, b, glyph; if (!hb_unicode_decompose (c->buffer->unicode, ab, &a, &b) || (b && !hb_font_get_glyph (c->font, b, 0, &glyph))) return FALSE; bool has_a = hb_font_get_glyph (c->font, a, 0, &glyph); if (shortest && has_a) { /* Output a and b */ output_glyph (c, a); if (b) output_glyph (c, b); return TRUE; } if (decompose (c, shortest, a)) { if (b) output_glyph (c, b); return TRUE; } if (has_a) { output_glyph (c, a); if (b) output_glyph (c, b); return TRUE; } return FALSE; } static void decompose_current_glyph (hb_ot_shape_context_t *c, bool shortest) { if (decompose (c, shortest, c->buffer->info[c->buffer->idx].codepoint)) c->buffer->skip_glyph (); else c->buffer->next_glyph (); } static void decompose_single_char_cluster (hb_ot_shape_context_t *c, bool will_recompose) { hb_codepoint_t glyph; /* If recomposing and font supports this, we're good to go */ if (will_recompose && hb_font_get_glyph (c->font, c->buffer->info[c->buffer->idx].codepoint, 0, &glyph)) { c->buffer->next_glyph (); return; } decompose_current_glyph (c, will_recompose); } static void decompose_multi_char_cluster (hb_ot_shape_context_t *c, unsigned int end) { /* TODO Currently if there's a variation-selector we give-up, it's just too hard. */ for (unsigned int i = c->buffer->idx; i < end; i++) if (unlikely (is_variation_selector (c->buffer->info[i].codepoint))) return; while (c->buffer->idx < end) decompose_current_glyph (c, FALSE); } static int compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb) { unsigned int a = pa->combining_class(); unsigned int b = pb->combining_class(); return a < b ? -1 : a == b ? 0 : +1; } void _hb_ot_shape_normalize (hb_ot_shape_context_t *c) { hb_buffer_t *buffer = c->buffer; bool recompose = !hb_ot_shape_complex_prefer_decomposed (c->plan->shaper); bool has_multichar_clusters = FALSE; unsigned int count; /* We do a fairly straightforward yet custom normalization process in three * separate rounds: decompose, reorder, recompose (if desired). Currently * this makes two buffer swaps. We can make it faster by moving the last * two rounds into the inner loop for the first round, but it's more readable * this way. */ /* First round, decompose */ buffer->clear_output (); count = buffer->len; for (buffer->idx = 0; buffer->idx < count;) { unsigned int end; for (end = buffer->idx + 1; end < count; end++) if (buffer->info[buffer->idx].cluster != buffer->info[end].cluster) break; if (buffer->idx + 1 == end) decompose_single_char_cluster (c, recompose); else { decompose_multi_char_cluster (c, end); has_multichar_clusters = TRUE; } } buffer->swap_buffers (); /* Technically speaking, two characters with ccc=0 may combine. But all * those cases are in languages that the indic module handles (which expects * decomposed), or in Hangul jamo, which again, we want decomposed anyway. * So we don't bother combining across cluster boundaries. * * TODO: Am I right about Hangul? If I am, we should add a Hangul module * that requests decomposed. */ if (!has_multichar_clusters) return; /* Done! */ /* Second round, reorder (inplace) */ count = buffer->len; for (unsigned int i = 0; i < count; i++) { if (buffer->info[i].combining_class() == 0) continue; unsigned int end; for (end = i + 1; end < count; end++) if (buffer->info[end].combining_class() == 0) break; /* We are going to do a bubble-sort. Only do this if the * sequence is short. Doing it on long sequences can result * in an O(n^2) DoS. */ if (end - i > 10) { i = end; continue; } hb_bubble_sort (buffer->info + i, end - i, compare_combining_class); i = end; } if (!recompose) return; /* Third round, recompose */ /* As noted in the comment earlier, we don't try to combine * ccc=0 chars with their previous Starter. */ buffer->clear_output (); count = buffer->len; unsigned int starter = 0; buffer->next_glyph (); while (buffer->idx < count) { if (buffer->info[buffer->idx].combining_class() == 0) { starter = buffer->out_len; buffer->next_glyph (); continue; } hb_codepoint_t composed, glyph; if ((buffer->out_info[buffer->out_len - 1].combining_class() >= buffer->info[buffer->idx].combining_class()) || !hb_unicode_compose (c->buffer->unicode, buffer->out_info[starter].codepoint, buffer->info[buffer->idx].codepoint, &composed) || !hb_font_get_glyph (c->font, composed, 0, &glyph)) { /* Blocked, or doesn't compose. */ buffer->next_glyph (); continue; } /* Composes. Modify starter and carry on. */ buffer->out_info[starter].codepoint = composed; hb_glyph_info_set_unicode_props (&buffer->out_info[starter], buffer->unicode); buffer->skip_glyph (); } buffer->swap_buffers (); }