HarfBuzz text shaping engine
http://harfbuzz.github.io/
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393 lines
12 KiB
393 lines
12 KiB
/* |
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* Copyright © 2010,2012 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.hh" |
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#ifndef HB_NO_OT_SHAPE |
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#include "hb-ot-shape-complex.hh" |
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/* Thai / Lao shaper */ |
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/* PUA shaping */ |
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enum thai_consonant_type_t |
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{ |
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NC, |
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AC, |
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RC, |
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DC, |
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NOT_CONSONANT, |
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NUM_CONSONANT_TYPES = NOT_CONSONANT |
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}; |
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static thai_consonant_type_t |
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get_consonant_type (hb_codepoint_t u) |
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{ |
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if (u == 0x0E1Bu || u == 0x0E1Du || u == 0x0E1Fu/* || u == 0x0E2Cu*/) |
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return AC; |
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if (u == 0x0E0Du || u == 0x0E10u) |
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return RC; |
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if (u == 0x0E0Eu || u == 0x0E0Fu) |
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return DC; |
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if (hb_in_range<hb_codepoint_t> (u, 0x0E01u, 0x0E2Eu)) |
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return NC; |
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return NOT_CONSONANT; |
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} |
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enum thai_mark_type_t |
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{ |
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AV, |
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BV, |
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T, |
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NOT_MARK, |
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NUM_MARK_TYPES = NOT_MARK |
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}; |
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static thai_mark_type_t |
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get_mark_type (hb_codepoint_t u) |
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{ |
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if (u == 0x0E31u || hb_in_range<hb_codepoint_t> (u, 0x0E34u, 0x0E37u) || |
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u == 0x0E47u || hb_in_range<hb_codepoint_t> (u, 0x0E4Du, 0x0E4Eu)) |
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return AV; |
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if (hb_in_range<hb_codepoint_t> (u, 0x0E38u, 0x0E3Au)) |
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return BV; |
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if (hb_in_range<hb_codepoint_t> (u, 0x0E48u, 0x0E4Cu)) |
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return T; |
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return NOT_MARK; |
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} |
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enum thai_action_t |
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{ |
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NOP, |
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SD, /* Shift combining-mark down */ |
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SL, /* Shift combining-mark left */ |
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SDL, /* Shift combining-mark down-left */ |
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RD /* Remove descender from base */ |
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}; |
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static hb_codepoint_t |
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thai_pua_shape (hb_codepoint_t u, thai_action_t action, hb_font_t *font) |
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{ |
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struct thai_pua_mapping_t { |
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hb_codepoint_t u; |
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hb_codepoint_t win_pua; |
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hb_codepoint_t mac_pua; |
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} const *pua_mappings = nullptr; |
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static const thai_pua_mapping_t SD_mappings[] = { |
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{0x0E48u, 0xF70Au, 0xF88Bu}, /* MAI EK */ |
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{0x0E49u, 0xF70Bu, 0xF88Eu}, /* MAI THO */ |
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{0x0E4Au, 0xF70Cu, 0xF891u}, /* MAI TRI */ |
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{0x0E4Bu, 0xF70Du, 0xF894u}, /* MAI CHATTAWA */ |
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{0x0E4Cu, 0xF70Eu, 0xF897u}, /* THANTHAKHAT */ |
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{0x0E38u, 0xF718u, 0xF89Bu}, /* SARA U */ |
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{0x0E39u, 0xF719u, 0xF89Cu}, /* SARA UU */ |
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{0x0E3Au, 0xF71Au, 0xF89Du}, /* PHINTHU */ |
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{0x0000u, 0x0000u, 0x0000u} |
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}; |
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static const thai_pua_mapping_t SDL_mappings[] = { |
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{0x0E48u, 0xF705u, 0xF88Cu}, /* MAI EK */ |
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{0x0E49u, 0xF706u, 0xF88Fu}, /* MAI THO */ |
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{0x0E4Au, 0xF707u, 0xF892u}, /* MAI TRI */ |
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{0x0E4Bu, 0xF708u, 0xF895u}, /* MAI CHATTAWA */ |
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{0x0E4Cu, 0xF709u, 0xF898u}, /* THANTHAKHAT */ |
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{0x0000u, 0x0000u, 0x0000u} |
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}; |
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static const thai_pua_mapping_t SL_mappings[] = { |
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{0x0E48u, 0xF713u, 0xF88Au}, /* MAI EK */ |
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{0x0E49u, 0xF714u, 0xF88Du}, /* MAI THO */ |
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{0x0E4Au, 0xF715u, 0xF890u}, /* MAI TRI */ |
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{0x0E4Bu, 0xF716u, 0xF893u}, /* MAI CHATTAWA */ |
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{0x0E4Cu, 0xF717u, 0xF896u}, /* THANTHAKHAT */ |
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{0x0E31u, 0xF710u, 0xF884u}, /* MAI HAN-AKAT */ |
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{0x0E34u, 0xF701u, 0xF885u}, /* SARA I */ |
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{0x0E35u, 0xF702u, 0xF886u}, /* SARA II */ |
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{0x0E36u, 0xF703u, 0xF887u}, /* SARA UE */ |
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{0x0E37u, 0xF704u, 0xF888u}, /* SARA UEE */ |
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{0x0E47u, 0xF712u, 0xF889u}, /* MAITAIKHU */ |
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{0x0E4Du, 0xF711u, 0xF899u}, /* NIKHAHIT */ |
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{0x0000u, 0x0000u, 0x0000u} |
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}; |
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static const thai_pua_mapping_t RD_mappings[] = { |
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{0x0E0Du, 0xF70Fu, 0xF89Au}, /* YO YING */ |
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{0x0E10u, 0xF700u, 0xF89Eu}, /* THO THAN */ |
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{0x0000u, 0x0000u, 0x0000u} |
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}; |
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switch (action) { |
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case NOP: return u; |
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case SD: pua_mappings = SD_mappings; break; |
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case SDL: pua_mappings = SDL_mappings; break; |
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case SL: pua_mappings = SL_mappings; break; |
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case RD: pua_mappings = RD_mappings; break; |
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} |
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for (; pua_mappings->u; pua_mappings++) |
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if (pua_mappings->u == u) |
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{ |
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hb_codepoint_t glyph; |
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if (hb_font_get_glyph (font, pua_mappings->win_pua, 0, &glyph)) |
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return pua_mappings->win_pua; |
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if (hb_font_get_glyph (font, pua_mappings->mac_pua, 0, &glyph)) |
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return pua_mappings->mac_pua; |
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break; |
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} |
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return u; |
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} |
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static enum thai_above_state_t |
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{ /* Cluster above looks like: */ |
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T0, /* ⣤ */ |
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T1, /* ⣼ */ |
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T2, /* ⣾ */ |
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T3, /* ⣿ */ |
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NUM_ABOVE_STATES |
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} thai_above_start_state[NUM_CONSONANT_TYPES + 1/* For NOT_CONSONANT */] = |
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{ |
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T0, /* NC */ |
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T1, /* AC */ |
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T0, /* RC */ |
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T0, /* DC */ |
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T3, /* NOT_CONSONANT */ |
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}; |
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static const struct thai_above_state_machine_edge_t { |
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thai_action_t action; |
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thai_above_state_t next_state; |
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} thai_above_state_machine[NUM_ABOVE_STATES][NUM_MARK_TYPES] = |
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{ /*AV*/ /*BV*/ /*T*/ |
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/*T0*/ {{NOP,T3}, {NOP,T0}, {SD, T3}}, |
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/*T1*/ {{SL, T2}, {NOP,T1}, {SDL,T2}}, |
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/*T2*/ {{NOP,T3}, {NOP,T2}, {SL, T3}}, |
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/*T3*/ {{NOP,T3}, {NOP,T3}, {NOP,T3}}, |
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}; |
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static enum thai_below_state_t |
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{ |
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B0, /* No descender */ |
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B1, /* Removable descender */ |
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B2, /* Strict descender */ |
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NUM_BELOW_STATES |
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} thai_below_start_state[NUM_CONSONANT_TYPES + 1/* For NOT_CONSONANT */] = |
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{ |
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B0, /* NC */ |
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B0, /* AC */ |
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B1, /* RC */ |
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B2, /* DC */ |
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B2, /* NOT_CONSONANT */ |
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}; |
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static const struct thai_below_state_machine_edge_t { |
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thai_action_t action; |
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thai_below_state_t next_state; |
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} thai_below_state_machine[NUM_BELOW_STATES][NUM_MARK_TYPES] = |
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{ /*AV*/ /*BV*/ /*T*/ |
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/*B0*/ {{NOP,B0}, {NOP,B2}, {NOP, B0}}, |
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/*B1*/ {{NOP,B1}, {RD, B2}, {NOP, B1}}, |
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/*B2*/ {{NOP,B2}, {SD, B2}, {NOP, B2}}, |
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}; |
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static void |
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do_thai_pua_shaping (const hb_ot_shape_plan_t *plan HB_UNUSED, |
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hb_buffer_t *buffer, |
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hb_font_t *font) |
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{ |
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#ifdef HB_NO_OT_SHAPE_COMPLEX_THAI_FALLBACK |
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return; |
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#endif |
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thai_above_state_t above_state = thai_above_start_state[NOT_CONSONANT]; |
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thai_below_state_t below_state = thai_below_start_state[NOT_CONSONANT]; |
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unsigned int base = 0; |
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hb_glyph_info_t *info = buffer->info; |
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unsigned int count = buffer->len; |
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for (unsigned int i = 0; i < count; i++) |
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{ |
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thai_mark_type_t mt = get_mark_type (info[i].codepoint); |
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if (mt == NOT_MARK) { |
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thai_consonant_type_t ct = get_consonant_type (info[i].codepoint); |
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above_state = thai_above_start_state[ct]; |
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below_state = thai_below_start_state[ct]; |
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base = i; |
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continue; |
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} |
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const thai_above_state_machine_edge_t &above_edge = thai_above_state_machine[above_state][mt]; |
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const thai_below_state_machine_edge_t &below_edge = thai_below_state_machine[below_state][mt]; |
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above_state = above_edge.next_state; |
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below_state = below_edge.next_state; |
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/* At least one of the above/below actions is NOP. */ |
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thai_action_t action = above_edge.action != NOP ? above_edge.action : below_edge.action; |
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buffer->unsafe_to_break (base, i); |
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if (action == RD) |
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info[base].codepoint = thai_pua_shape (info[base].codepoint, action, font); |
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else |
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info[i].codepoint = thai_pua_shape (info[i].codepoint, action, font); |
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} |
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} |
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static void |
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preprocess_text_thai (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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/* This function implements the shaping logic documented here: |
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* |
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* https://linux.thai.net/~thep/th-otf/shaping.html |
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* |
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* The first shaping rule listed there is needed even if the font has Thai |
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* OpenType tables. The rest do fallback positioning based on PUA codepoints. |
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* We implement that only if there exist no Thai GSUB in the font. |
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*/ |
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/* The following is NOT specified in the MS OT Thai spec, however, it seems |
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* to be what Uniscribe and other engines implement. According to Eric Muller: |
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* |
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* When you have a SARA AM, decompose it in NIKHAHIT + SARA AA, *and* move the |
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* NIKHAHIT backwards over any tone mark (0E48-0E4B). |
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* |
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* <0E14, 0E4B, 0E33> -> <0E14, 0E4D, 0E4B, 0E32> |
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* |
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* This reordering is legit only when the NIKHAHIT comes from a SARA AM, not |
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* when it's there to start with. The string <0E14, 0E4B, 0E4D> is probably |
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* not what a user wanted, but the rendering is nevertheless nikhahit above |
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* chattawa. |
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* |
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* Same for Lao. |
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* |
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* Note: |
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* |
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* Uniscribe also does some below-marks reordering. Namely, it positions U+0E3A |
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* after U+0E38 and U+0E39. We do that by modifying the ccc for U+0E3A. |
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* See unicode->modified_combining_class (). Lao does NOT have a U+0E3A |
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* equivalent. |
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*/ |
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/* |
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* Here are the characters of significance: |
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* |
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* Thai Lao |
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* SARA AM: U+0E33 U+0EB3 |
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* SARA AA: U+0E32 U+0EB2 |
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* Nikhahit: U+0E4D U+0ECD |
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* |
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* Testing shows that Uniscribe reorder the following marks: |
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* Thai: <0E31,0E34..0E37,0E47..0E4E> |
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* Lao: <0EB1,0EB4..0EB7,0EC7..0ECE> |
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* |
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* Note how the Lao versions are the same as Thai + 0x80. |
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*/ |
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/* We only get one script at a time, so a script-agnostic implementation |
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* is adequate here. */ |
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#define IS_SARA_AM(x) (((x) & ~0x0080u) == 0x0E33u) |
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#define NIKHAHIT_FROM_SARA_AM(x) ((x) - 0x0E33u + 0x0E4Du) |
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#define SARA_AA_FROM_SARA_AM(x) ((x) - 1) |
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#define IS_TONE_MARK(x) (hb_in_ranges<hb_codepoint_t> ((x) & ~0x0080u, 0x0E34u, 0x0E37u, 0x0E47u, 0x0E4Eu, 0x0E31u, 0x0E31u)) |
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buffer->clear_output (); |
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unsigned int count = buffer->len; |
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for (buffer->idx = 0; buffer->idx < count /* No need for: && buffer->successful */;) |
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{ |
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hb_codepoint_t u = buffer->cur().codepoint; |
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if (likely (!IS_SARA_AM (u))) |
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{ |
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if (unlikely (!buffer->next_glyph ())) break; |
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continue; |
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} |
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/* Is SARA AM. Decompose and reorder. */ |
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(void) buffer->output_glyph (NIKHAHIT_FROM_SARA_AM (u)); |
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_hb_glyph_info_set_continuation (&buffer->prev()); |
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if (unlikely (!buffer->replace_glyph (SARA_AA_FROM_SARA_AM (u)))) break; |
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/* Make Nikhahit be recognized as a ccc=0 mark when zeroing widths. */ |
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unsigned int end = buffer->out_len; |
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_hb_glyph_info_set_general_category (&buffer->out_info[end - 2], HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK); |
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/* Ok, let's see... */ |
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unsigned int start = end - 2; |
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while (start > 0 && IS_TONE_MARK (buffer->out_info[start - 1].codepoint)) |
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start--; |
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if (start + 2 < end) |
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{ |
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/* Move Nikhahit (end-2) to the beginning */ |
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buffer->merge_out_clusters (start, end); |
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hb_glyph_info_t t = buffer->out_info[end - 2]; |
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memmove (buffer->out_info + start + 1, |
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buffer->out_info + start, |
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sizeof (buffer->out_info[0]) * (end - start - 2)); |
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buffer->out_info[start] = t; |
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} |
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else |
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{ |
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/* Since we decomposed, and NIKHAHIT is combining, merge clusters with the |
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* previous cluster. */ |
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if (start && buffer->cluster_level == HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES) |
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buffer->merge_out_clusters (start - 1, end); |
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} |
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} |
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buffer->sync (); |
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/* If font has Thai GSUB, we are done. */ |
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if (plan->props.script == HB_SCRIPT_THAI && !plan->map.found_script[0]) |
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do_thai_pua_shaping (plan, buffer, font); |
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} |
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const hb_ot_complex_shaper_t _hb_ot_complex_shaper_thai = |
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{ |
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nullptr, /* collect_features */ |
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nullptr, /* override_features */ |
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nullptr, /* data_create */ |
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nullptr, /* data_destroy */ |
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preprocess_text_thai, |
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nullptr, /* postprocess_glyphs */ |
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HB_OT_SHAPE_NORMALIZATION_MODE_DEFAULT, |
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nullptr, /* decompose */ |
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nullptr, /* compose */ |
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nullptr, /* setup_masks */ |
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HB_TAG_NONE, /* gpos_tag */ |
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nullptr, /* reorder_marks */ |
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HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_GDEF_LATE, |
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false,/* fallback_position */ |
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}; |
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#endif
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