/* * Copyright © 2011,2012 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-normalize-private.hh" #include "hb-ot-shape-complex-private.hh" #include "hb-ot-shape-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. * * Each shaper specifies whether it prefers decomposed (NFD) or composed (NFC). * The logic however tries to use whatever the font can support. * * In general what happens is that: each grapheme is decomposed in a chain * of 1:2 decompositions, marks reordered, and then recomposed if desired, * 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, use the precomposed character * which typically has better mark positioning. * * - When a font does not support a combining mark, but supports it precomposed * with previous base, use that. This needs the itemizer to have this * knowledge too. We need to provide assistance to the itemizer. * * - When a font does not support a character but supports its decomposition, * well, use the decomposition (preferring the canonical decomposition, but * falling back to the compatibility decomposition if necessary). The * compatibility decomposition is really nice to have, for characters like * ellipsis, or various-sized space characters. * * - The complex shapers can customize the compose and decompose functions to * offload some of their requirements to the normalizer. For example, the * Indic shaper may want to disallow recomposing of two matras. * * - We try compatibility decomposition if decomposing through canonical * decomposition alone failed to find a sequence that the font supports. * We don't try compatibility decomposition recursively during the canonical * decomposition phase. This has minimal impact. There are only a handful * of Greek letter that have canonical decompositions that include characters * with compatibility decomposition. Those can be found using this command: * * egrep "`echo -n ';('; grep ';<' UnicodeData.txt | cut -d';' -f1 | tr '\n' '|'; echo ') '`" UnicodeData.txt */ static bool decompose_unicode (const hb_ot_shape_normalize_context_t *c, hb_codepoint_t ab, hb_codepoint_t *a, hb_codepoint_t *b) { return c->unicode->decompose (ab, a, b); } static bool compose_unicode (const hb_ot_shape_normalize_context_t *c, hb_codepoint_t a, hb_codepoint_t b, hb_codepoint_t *ab) { return c->unicode->compose (a, b, ab); } static inline void set_glyph (hb_glyph_info_t &info, hb_font_t *font) { font->get_glyph (info.codepoint, 0, &info.glyph_index()); } static inline void output_char (hb_buffer_t *buffer, hb_codepoint_t unichar, hb_codepoint_t glyph) { buffer->cur().glyph_index() = glyph; buffer->output_glyph (unichar); _hb_glyph_info_set_unicode_props (&buffer->prev(), buffer->unicode); } static inline void next_char (hb_buffer_t *buffer, hb_codepoint_t glyph) { buffer->cur().glyph_index() = glyph; buffer->next_glyph (); } static inline void skip_char (hb_buffer_t *buffer) { buffer->skip_glyph (); } /* Returns 0 if didn't decompose, number of resulting characters otherwise. */ static inline unsigned int decompose (const hb_ot_shape_normalize_context_t *c, bool shortest, hb_codepoint_t ab) { hb_codepoint_t a, b, a_glyph, b_glyph; hb_buffer_t * const buffer = c->buffer; hb_font_t * const font = c->font; if (!c->decompose (c, ab, &a, &b) || (b && !font->get_glyph (b, 0, &b_glyph))) return 0; bool has_a = font->get_glyph (a, 0, &a_glyph); if (shortest && has_a) { /* Output a and b */ output_char (buffer, a, a_glyph); if (likely (b)) { output_char (buffer, b, b_glyph); return 2; } return 1; } unsigned int ret; if ((ret = decompose (c, shortest, a))) { if (b) { output_char (buffer, b, b_glyph); return ret + 1; } return ret; } if (has_a) { output_char (buffer, a, a_glyph); if (likely (b)) { output_char (buffer, b, b_glyph); return 2; } return 1; } return 0; } static inline void decompose_current_character (const hb_ot_shape_normalize_context_t *c, bool shortest) { hb_buffer_t * const buffer = c->buffer; hb_codepoint_t u = buffer->cur().codepoint; hb_codepoint_t glyph; /* Kind of a cute waterfall here... */ if (shortest && c->font->get_glyph (u, 0, &glyph)) next_char (buffer, glyph); else if (decompose (c, shortest, u)) skip_char (buffer); else if (!shortest && c->font->get_glyph (u, 0, &glyph)) next_char (buffer, glyph); else next_char (buffer, glyph); /* glyph is initialized in earlier branches. */ } static inline void handle_variation_selector_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool short_circuit) { /* TODO Currently if there's a variation-selector we give-up, it's just too hard. */ hb_buffer_t * const buffer = c->buffer; hb_font_t * const font = c->font; for (; buffer->idx < end - 1;) { if (unlikely (buffer->unicode->is_variation_selector (buffer->cur(+1).codepoint))) { /* The next two lines are some ugly lines... But work. */ if (font->get_glyph (buffer->cur().codepoint, buffer->cur(+1).codepoint, &buffer->cur().glyph_index())) { buffer->replace_glyphs (2, 1, &buffer->cur().codepoint); } else { /* Just pass on the two characters separately, let GSUB do its magic. */ set_glyph (buffer->cur(), font); buffer->next_glyph (); set_glyph (buffer->cur(), font); buffer->next_glyph (); } /* Skip any further variation selectors. */ while (buffer->idx < end && unlikely (buffer->unicode->is_variation_selector (buffer->cur().codepoint))) { set_glyph (buffer->cur(), font); buffer->next_glyph (); } } else { set_glyph (buffer->cur(), font); buffer->next_glyph (); } } if (likely (buffer->idx < end)) { set_glyph (buffer->cur(), font); buffer->next_glyph (); } } static inline void decompose_multi_char_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool short_circuit) { hb_buffer_t * const buffer = c->buffer; for (unsigned int i = buffer->idx; i < end; i++) if (unlikely (buffer->unicode->is_variation_selector (buffer->info[i].codepoint))) { handle_variation_selector_cluster (c, end, short_circuit); return; } while (buffer->idx < end) decompose_current_character (c, short_circuit); } static inline void decompose_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool might_short_circuit, bool always_short_circuit) { if (likely (c->buffer->idx + 1 == end)) decompose_current_character (c, might_short_circuit); else decompose_multi_char_cluster (c, end, always_short_circuit); } static int compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb) { unsigned int a = _hb_glyph_info_get_modified_combining_class (pa); unsigned int b = _hb_glyph_info_get_modified_combining_class (pb); return a < b ? -1 : a == b ? 0 : +1; } void _hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan, hb_buffer_t *buffer, hb_font_t *font) { if (unlikely (!buffer->len)) return; _hb_buffer_assert_unicode_vars (buffer); hb_ot_shape_normalization_mode_t mode = plan->shaper->normalization_preference; const hb_ot_shape_normalize_context_t c = { plan, buffer, font, buffer->unicode, plan->shaper->decompose ? plan->shaper->decompose : decompose_unicode, plan->shaper->compose ? plan->shaper->compose : compose_unicode }; bool always_short_circuit = mode == HB_OT_SHAPE_NORMALIZATION_MODE_NONE; bool might_short_circuit = always_short_circuit || (mode != HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED && mode != HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT); 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 (likely (!HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->info[end])))) break; decompose_cluster (&c, end, might_short_circuit, always_short_circuit); } buffer->swap_buffers (); /* Second round, reorder (inplace) */ count = buffer->len; for (unsigned int i = 0; i < count; i++) { if (_hb_glyph_info_get_modified_combining_class (&buffer->info[i]) == 0) continue; unsigned int end; for (end = i + 1; end < count; end++) if (_hb_glyph_info_get_modified_combining_class (&buffer->info[end]) == 0) break; /* We are going to do a O(n^2). Only do this if the sequence is short. */ if (end - i > 10) { i = end; continue; } buffer->sort (i, end, compare_combining_class); i = end; } if (mode == HB_OT_SHAPE_NORMALIZATION_MODE_NONE || mode == HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED) 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) { hb_codepoint_t composed, glyph; if (/* We don't try to compose a non-mark character with it's preceding starter. * This is both an optimization to avoid trying to compose every two neighboring * glyphs in most scripts AND a desired feature for Hangul. Apparently Hangul * fonts are not designed to mix-and-match pre-composed syllables and Jamo. */ HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->cur())) && /* If there's anything between the starter and this char, they should have CCC * smaller than this character's. */ (starter == buffer->out_len - 1 || _hb_glyph_info_get_modified_combining_class (&buffer->prev()) < _hb_glyph_info_get_modified_combining_class (&buffer->cur())) && /* And compose. */ c.compose (&c, buffer->out_info[starter].codepoint, buffer->cur().codepoint, &composed) && /* And the font has glyph for the composite. */ font->get_glyph (composed, 0, &glyph)) { /* Composes. */ buffer->next_glyph (); /* Copy to out-buffer. */ if (unlikely (buffer->in_error)) return; buffer->merge_out_clusters (starter, buffer->out_len); buffer->out_len--; /* Remove the second composable. */ /* Modify starter and carry on. */ buffer->out_info[starter].codepoint = composed; buffer->out_info[starter].glyph_index() = glyph; _hb_glyph_info_set_unicode_props (&buffer->out_info[starter], buffer->unicode); continue; } /* Blocked, or doesn't compose. */ buffer->next_glyph (); if (_hb_glyph_info_get_modified_combining_class (&buffer->prev()) == 0) starter = buffer->out_len - 1; } buffer->swap_buffers (); }