harfbuzz/src/hb-ot-shape-complex-thai.cc

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2011-07-08 04:35:17 +02:00
/*
* Copyright © 2010,2012 Google, Inc.
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*
* 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-complex-private.hh"
/* Thai / Lao shaper */
static void
preprocess_text_thai (const hb_ot_shape_plan_t *plan HB_UNUSED,
hb_buffer_t *buffer,
hb_font_t *font HB_UNUSED)
{
/* The following is NOT specified in the MS OT Thai spec, however, it seems
* to be what Uniscribe and other engines implement. According to Eric Muller:
*
* When you have a SARA AM, decompose it in NIKHAHIT + SARA AA, *and* move the
* NIKHAHIT backwards over any tone mark (0E48-0E4B).
*
* <0E14, 0E4B, 0E33> -> <0E14, 0E4D, 0E4B, 0E32>
*
* This reordering is legit only when the NIKHAHIT comes from a SARA AM, not
* when it's there to start with. The string <0E14, 0E4B, 0E4D> is probably
* not what a user wanted, but the rendering is nevertheless nikhahit above
* chattawa.
*
* Same for Lao.
*
* Note:
*
2012-11-15 00:51:54 +01:00
* Uniscribe also does some below-marks reordering. Namely, it positions U+0E3A
* after U+0E38 and U+0E39. We do that by modifying the ccc for U+0E3A.
2012-08-01 23:13:10 +02:00
* See unicode->modified_combining_class (). Lao does NOT have a U+0E3A
* equivalent.
*/
/*
* Here are the characters of significance:
*
* Thai Lao
* SARA AM: U+0E33 U+0EB3
* SARA AA: U+0E32 U+0EB2
* Nikhahit: U+0E4D U+0ECD
*
* Testing shows that Uniscribe reorder the following marks:
* Thai: <0E31,0E34..0E37,0E47..0E4E>
* Lao: <0EB1,0EB4..0EB7,0EC7..0ECE>
*
* Note how the Lao versions are the same as Thai + 0x80.
*/
/* We only get one script at a time, so a script-agnostic implementation
* is adequate here. */
#define IS_SARA_AM(x) (((x) & ~0x0080) == 0x0E33)
#define NIKHAHIT_FROM_SARA_AM(x) ((x) - 0xE33 + 0xE4D)
#define SARA_AA_FROM_SARA_AM(x) ((x) - 1)
#define IS_TONE_MARK(x) (hb_in_ranges<hb_codepoint_t> ((x) & ~0x0080, 0x0E34, 0x0E37, 0x0E47, 0x0E4E, 0x0E31, 0x0E31))
buffer->clear_output ();
unsigned int count = buffer->len;
for (buffer->idx = 0; buffer->idx < count;)
{
hb_codepoint_t u = buffer->cur().codepoint;
if (likely (!IS_SARA_AM (u))) {
buffer->next_glyph ();
continue;
}
/* Is SARA AM. Decompose and reorder. */
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hb_codepoint_t decomposed[2] = {hb_codepoint_t (NIKHAHIT_FROM_SARA_AM (u)),
hb_codepoint_t (SARA_AA_FROM_SARA_AM (u))};
buffer->replace_glyphs (1, 2, decomposed);
if (unlikely (buffer->in_error))
return;
/* Ok, let's see... */
unsigned int end = buffer->out_len;
unsigned int start = end - 2;
while (start > 0 && IS_TONE_MARK (buffer->out_info[start - 1].codepoint))
start--;
if (start + 2 < end)
{
/* Move Nikhahit (end-2) to the beginning */
buffer->merge_out_clusters (start, end);
hb_glyph_info_t t = buffer->out_info[end - 2];
memmove (buffer->out_info + start + 1,
buffer->out_info + start,
sizeof (buffer->out_info[0]) * (end - start - 2));
buffer->out_info[start] = t;
}
else
{
/* Since we decomposed, and NIKHAHIT is combining, merge clusters with the
* previous cluster. */
if (start)
buffer->merge_out_clusters (start - 1, end);
}
}
buffer->swap_buffers ();
}
const hb_ot_complex_shaper_t _hb_ot_complex_shaper_thai =
{
"thai",
NULL, /* collect_features */
NULL, /* override_features */
NULL, /* data_create */
NULL, /* data_destroy */
preprocess_text_thai,
NULL, /* normalization_preference */
NULL, /* decompose */
NULL, /* compose */
NULL, /* setup_masks */
true, /* zero_width_attached_marks */
false,/* fallback_position */
};