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Diffstat (limited to 'gfx/harfbuzz/src/hb-ot-shape-normalize.cc')
| -rw-r--r-- | gfx/harfbuzz/src/hb-ot-shape-normalize.cc | 415 |
1 files changed, 415 insertions, 0 deletions
diff --git a/gfx/harfbuzz/src/hb-ot-shape-normalize.cc b/gfx/harfbuzz/src/hb-ot-shape-normalize.cc new file mode 100644 index 000000000..107617e81 --- /dev/null +++ b/gfx/harfbuzz/src/hb-ot-shape-normalize.cc @@ -0,0 +1,415 @@ +/* + * 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 canonical + * decomposition, well, use the decomposition. + * + * - 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. + */ + +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 (bool) 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 (bool) c->unicode->compose (a, b, ab); +} + +static inline void +set_glyph (hb_glyph_info_t &info, hb_font_t *font) +{ + font->get_nominal_glyph (info.codepoint, &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); /* This is very confusing indeed. */ + _hb_glyph_info_set_unicode_props (&buffer->prev(), buffer); +} + +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_nominal_glyph (b, &b_glyph))) + return 0; + + bool has_a = (bool) font->get_nominal_glyph (a, &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; + + if (shortest && c->font->get_nominal_glyph (u, &glyph)) + { + next_char (buffer, glyph); + return; + } + + if (decompose (c, shortest, u)) + { + skip_char (buffer); + return; + } + + if (!shortest && c->font->get_nominal_glyph (u, &glyph)) + { + next_char (buffer, glyph); + return; + } + + if (_hb_glyph_info_is_unicode_space (&buffer->cur())) + { + hb_codepoint_t space_glyph; + hb_unicode_funcs_t::space_t space_type = buffer->unicode->space_fallback_type (u); + if (space_type != hb_unicode_funcs_t::NOT_SPACE && c->font->get_nominal_glyph (0x0020u, &space_glyph)) + { + _hb_glyph_info_set_unicode_space_fallback_type (&buffer->cur(), space_type); + next_char (buffer, space_glyph); + buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_SPACE_FALLBACK; + return; + } + } + + if (u == 0x2011u) + { + /* U+2011 is the only sensible character that is a no-break version of another character + * and not a space. The space ones are handled already. Handle this lone one. */ + hb_codepoint_t other_glyph; + if (c->font->get_nominal_glyph (0x2010u, &other_glyph)) + { + next_char (buffer, other_glyph); + return; + } + } + + 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 && !buffer->in_error;) { + if (unlikely (buffer->unicode->is_variation_selector (buffer->cur(+1).codepoint))) { + /* The next two lines are some ugly lines... But work. */ + if (font->get_variation_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 && !buffer->in_error; 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 && !buffer->in_error) + 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 && !buffer->in_error;) + { + 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 && !buffer->in_error) + { + 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_nominal_glyph (composed, &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); + + 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 (); + +} |