[Thai] Implement PUA-based fallback shaping
As explained here: http://linux.thai.net/~thep/th-otf/shaping.html Our output now matches Uniscribe for old fonts (eg. XP Tahoma) with no Thai GSUB table.
This commit is contained in:
Behdad Esfahbod
parent
851784f837
commit
1eb3e94fe9
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@ -29,13 +29,230 @@
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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 == 0x0E1B || u == 0x0E1D || u == 0x0E1F || u == 0x0E2C)
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return AC;
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if (u == 0x0E0D || u == 0x0E10)
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return RC;
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if (u == 0x0E0E || u == 0x0E0F)
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return DC;
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if (hb_in_range<hb_codepoint_t> (u, 0x0E01, 0x0E2E))
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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 == 0x0E31 || hb_in_range<hb_codepoint_t> (u, 0x0E34, 0x0E37) ||
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u == 0x0E47 || hb_in_range<hb_codepoint_t> (u, 0x0E4D, 0x0E4E))
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return AV;
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if (hb_in_range<hb_codepoint_t> (u, 0x0E38, 0x0E3A))
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return BV;
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if (hb_in_range<hb_codepoint_t> (u, 0x0E48, 0x0E4C))
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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 = NULL;
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static const thai_pua_mapping_t SD_mappings[] = {
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{0x0E48, 0xF70A, 0xF88B}, /* MAI EK */
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{0x0E49, 0xF70B, 0xF88E}, /* MAI THO */
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{0x0E4A, 0xF70C, 0xF891}, /* MAI TRI */
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{0x0E4B, 0xF70D, 0xF894}, /* MAI CHATTAWA */
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{0x0E4C, 0xF70E, 0xF897}, /* THANTHAKHAT */
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{0x0E38, 0xF718, 0xF89B}, /* SARA U */
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{0x0E39, 0xF719, 0xF89C}, /* SARA UU */
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{0x0E3A, 0xF71A, 0xF89D}, /* PHINTHU */
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{0x0000, 0x0000, 0x0000}
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};
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static const thai_pua_mapping_t SDL_mappings[] = {
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{0x0E48, 0xF705, 0xF88C}, /* MAI EK */
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{0x0E49, 0xF706, 0xF88F}, /* MAI THO */
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{0x0E4A, 0xF707, 0xF892}, /* MAI TRI */
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{0x0E4B, 0xF708, 0xF895}, /* MAI CHATTAWA */
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{0x0E4C, 0xF709, 0xF898}, /* THANTHAKHAT */
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{0x0000, 0x0000, 0x0000}
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};
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static const thai_pua_mapping_t SL_mappings[] = {
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{0x0E48, 0xF713, 0xF88A}, /* MAI EK */
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{0x0E49, 0xF714, 0xF88D}, /* MAI THO */
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{0x0E4A, 0xF715, 0xF890}, /* MAI TRI */
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{0x0E4B, 0xF716, 0xF893}, /* MAI CHATTAWA */
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{0x0E4C, 0xF717, 0xF896}, /* THANTHAKHAT */
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{0x0E31, 0xF710, 0xF884}, /* MAI HAN-AKAT */
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{0x0E34, 0xF701, 0xF885}, /* SARA I */
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{0x0E35, 0xF702, 0xF886}, /* SARA II */
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{0x0E36, 0xF703, 0xF887}, /* SARA UE */
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{0x0E37, 0xF704, 0xF888}, /* SARA UEE */
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{0x0E47, 0xF712, 0xF889}, /* MAITAIKHU */
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{0x0E4D, 0xF711, 0xF899}, /* NIKHAHIT */
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{0x0000, 0x0000, 0x0000}
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};
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static const thai_pua_mapping_t RD_mappings[] = {
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{0x0E0D, 0xF70F, 0xF89A}, /* YO YING */
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{0x0E10, 0xF700, 0xF89E}, /* THO THAN */
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{0x0000, 0x0000, 0x0000}
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};
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switch (action) {
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default: assert (false); /* Fallthrough */
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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,
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hb_buffer_t *buffer,
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hb_font_t *font)
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{
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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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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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