Behdad Esfahbod
12 years ago
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3 changed files with 143 additions and 115 deletions
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/*
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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-ot-shape-complex-private.hh" |
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/* Thai / Lao shaper */ |
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static void |
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preprocess_text_thai (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 HB_UNUSED) |
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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) & ~0x0080) == 0x0E33) |
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#define NIKHAHIT_FROM_SARA_AM(x) ((x) - 0xE33 + 0xE4D) |
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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) & ~0x0080, 0x0E34, 0x0E37, 0x0E47, 0x0E4E, 0x0E31, 0x0E31)) |
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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;) |
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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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buffer->next_glyph (); |
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continue; |
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} |
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/* Is SARA AM. Decompose and reorder. */ |
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hb_codepoint_t decomposed[2] = {hb_codepoint_t (NIKHAHIT_FROM_SARA_AM (u)), |
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hb_codepoint_t (SARA_AA_FROM_SARA_AM (u))}; |
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buffer->replace_glyphs (1, 2, decomposed); |
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if (unlikely (buffer->in_error)) |
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return; |
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/* Ok, let's see... */ |
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unsigned int end = buffer->out_len; |
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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) |
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buffer->merge_out_clusters (start - 1, end); |
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} |
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} |
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buffer->swap_buffers (); |
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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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"thai", |
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NULL, /* collect_features */ |
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NULL, /* override_features */ |
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NULL, /* data_create */ |
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NULL, /* data_destroy */ |
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preprocess_text_thai, |
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NULL, /* normalization_preference */ |
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NULL, /* decompose */ |
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NULL, /* compose */ |
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NULL, /* setup_masks */ |
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true, /* zero_width_attached_marks */ |
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false,/* fallback_position */ |
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}; |
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