chromium/third_party/harfbuzz-ng/src/src/hb-ot-shape-normalize.cc

/*
 * 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.hh"

#ifndef HB_NO_OT_SHAPE

#include "hb-ot-shape-normalize.hh"
#include "hb-ot-shaper.hh"
#include "hb-ot-shape.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 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)
{ … }

static bool
compose_unicode (const hb_ot_shape_normalize_context_t *c,
		 hb_codepoint_t  a,
		 hb_codepoint_t  b,
		 hb_codepoint_t *ab)
{ … }

static inline void
set_glyph (hb_glyph_info_t &info, hb_font_t *font)
{ … }

static inline void
output_char (hb_buffer_t *buffer, hb_codepoint_t unichar, hb_codepoint_t glyph)
{ … }

static inline void
next_char (hb_buffer_t *buffer, hb_codepoint_t glyph)
{ … }

static inline void
skip_char (hb_buffer_t *buffer)
{ … }

/* 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)
{ … }

static inline void
decompose_current_character (const hb_ot_shape_normalize_context_t *c, bool shortest)
{ … }

static inline void
handle_variation_selector_cluster (const hb_ot_shape_normalize_context_t *c,
				   unsigned int end,
				   bool short_circuit HB_UNUSED)
{ … }

static inline void
decompose_multi_char_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool short_circuit)
{ … }


static int
compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb)
{ … }


void
_hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan,
			hb_buffer_t *buffer,
			hb_font_t *font)
{ … }


#endif