/*
* 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)
{
(void) 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,
* but not too short ;). */
if (end - i < 2 || end - i > HB_OT_SHAPE_COMPLEX_MAX_COMBINING_MARKS) {
i = end;
continue;
}
buffer->sort (i, end, compare_combining_class);
if (plan->shaper->reorder_marks)
plan->shaper->reorder_marks (plan, buffer, i, end);
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;
bool combine = true;
buffer->next_glyph ();
while (buffer->idx < count && !buffer->in_error)
{
hb_codepoint_t composed, glyph;
if (combine &&
/* 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 (/* If there's anything between the starter and this char, they should have CCC
* smaller than this character's. */
(starter == buffer->out_len - 1 ||
info_cc (buffer->prev()) < info_cc (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;
}
else if (/* We sometimes custom-tailor the sorted order of marks. In that case, stop
* trying to combine as soon as combining-class drops. */
starter < buffer->out_len - 1 &&
info_cc (buffer->prev()) > info_cc (buffer->cur()))
combine = false;
}
/* Blocked, or doesn't compose. */
buffer->next_glyph ();
if (info_cc (buffer->prev()) == 0)
{
starter = buffer->out_len - 1;
combine = true;
}
}
buffer->swap_buffers ();
}