harfbuzz/src/hb-ot-shape-complex-khmer.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-complex-khmer.hh"
#include "hb-ot-layout.hh"

/*
 * Khmer shaper.
 */

static const hb_ot_map_feature_t khmer_features[] = {
    /*
     * Basic features.
     * These features are applied in order, one at a time, after reordering.
     */
    {HB_TAG('p', 'r', 'e', 'f'), F_MANUAL_JOINERS},
    {HB_TAG('b', 'l', 'w', 'f'), F_MANUAL_JOINERS},
    {HB_TAG('a', 'b', 'v', 'f'), F_MANUAL_JOINERS},
    {HB_TAG('p', 's', 't', 'f'), F_MANUAL_JOINERS},
    {HB_TAG('c', 'f', 'a', 'r'), F_MANUAL_JOINERS},
    /*
     * Other features.
     * These features are applied all at once after clearing syllables.
     */
    {HB_TAG('p', 'r', 'e', 's'), F_GLOBAL_MANUAL_JOINERS},
    {HB_TAG('a', 'b', 'v', 's'), F_GLOBAL_MANUAL_JOINERS},
    {HB_TAG('b', 'l', 'w', 's'), F_GLOBAL_MANUAL_JOINERS},
    {HB_TAG('p', 's', 't', 's'), F_GLOBAL_MANUAL_JOINERS},
};

/*
 * Must be in the same order as the khmer_features array.
 */
enum {
    KHMER_PREF,
    KHMER_BLWF,
    KHMER_ABVF,
    KHMER_PSTF,
    KHMER_CFAR,

    _KHMER_PRES,
    _KHMER_ABVS,
    _KHMER_BLWS,
    _KHMER_PSTS,

    KHMER_NUM_FEATURES,
    KHMER_BASIC_FEATURES = _KHMER_PRES, /* Don't forget to update this! */
};

static void setup_syllables_khmer(const hb_ot_shape_plan_t *plan, hb_font_t *font, hb_buffer_t *buffer);
static void reorder_khmer(const hb_ot_shape_plan_t *plan, hb_font_t *font, hb_buffer_t *buffer);

static void collect_features_khmer(hb_ot_shape_planner_t *plan)
{
    hb_ot_map_builder_t *map = &plan->map;

    /* Do this before any lookups have been applied. */
    map->add_gsub_pause(setup_syllables_khmer);
    map->add_gsub_pause(reorder_khmer);

    /* Testing suggests that Uniscribe does NOT pause between basic
     * features.  Test with KhmerUI.ttf and the following three
     * sequences:
     *
     *   U+1789,U+17BC
     *   U+1789,U+17D2,U+1789
     *   U+1789,U+17D2,U+1789,U+17BC
     *
     * https://github.com/harfbuzz/harfbuzz/issues/974
     */
    map->enable_feature(HB_TAG('l', 'o', 'c', 'l'));
    map->enable_feature(HB_TAG('c', 'c', 'm', 'p'));

    unsigned int i = 0;
    for (; i < KHMER_BASIC_FEATURES; i++)
        map->add_feature(khmer_features[i]);

    map->add_gsub_pause(_hb_clear_syllables);

    for (; i < KHMER_NUM_FEATURES; i++)
        map->add_feature(khmer_features[i]);
}

static void override_features_khmer(hb_ot_shape_planner_t *plan)
{
    hb_ot_map_builder_t *map = &plan->map;

    /* Khmer spec has 'clig' as part of required shaping features:
     * "Apply feature 'clig' to form ligatures that are desired for
     * typographical correctness.", hence in overrides... */
    map->enable_feature(HB_TAG('c', 'l', 'i', 'g'));

    /* Uniscribe does not apply 'kern' in Khmer. */
    if (hb_options().uniscribe_bug_compatible) {
        map->disable_feature(HB_TAG('k', 'e', 'r', 'n'));
    }

    map->disable_feature(HB_TAG('l', 'i', 'g', 'a'));
}

struct khmer_shape_plan_t
{
    bool get_virama_glyph(hb_font_t *font, hb_codepoint_t *pglyph) const
    {
        hb_codepoint_t glyph = virama_glyph;
        if (unlikely(virama_glyph == (hb_codepoint_t)-1)) {
            if (!font->get_nominal_glyph(0x17D2u, &glyph))
                glyph = 0;
            /* Technically speaking, the spec says we should apply 'locl' to virama too.
             * Maybe one day... */

            /* Our get_nominal_glyph() function needs a font, so we can't get the virama glyph
             * during shape planning...  Instead, overwrite it here.  It's safe.  Don't worry! */
            virama_glyph = glyph;
        }

        *pglyph = glyph;
        return glyph != 0;
    }

    mutable hb_codepoint_t virama_glyph;

    hb_indic_would_substitute_feature_t pref;

    hb_mask_t mask_array[KHMER_NUM_FEATURES];
};

static void *data_create_khmer(const hb_ot_shape_plan_t *plan)
{
    khmer_shape_plan_t *khmer_plan = (khmer_shape_plan_t *)calloc(1, sizeof(khmer_shape_plan_t));
    if (unlikely(!khmer_plan))
        return nullptr;

    khmer_plan->virama_glyph = (hb_codepoint_t)-1;

    khmer_plan->pref.init(&plan->map, HB_TAG('p', 'r', 'e', 'f'), true);

    for (unsigned int i = 0; i < ARRAY_LENGTH(khmer_plan->mask_array); i++)
        khmer_plan->mask_array[i] =
            (khmer_features[i].flags & F_GLOBAL) ? 0 : plan->map.get_1_mask(khmer_features[i].tag);

    return khmer_plan;
}

static void data_destroy_khmer(void *data)
{
    free(data);
}

enum khmer_syllable_type_t {
    khmer_consonant_syllable,
    khmer_broken_cluster,
    khmer_non_khmer_cluster,
};

#include "hb-ot-shape-complex-khmer-machine.hh"

static void setup_masks_khmer(const hb_ot_shape_plan_t *plan HB_UNUSED, hb_buffer_t *buffer, hb_font_t *font HB_UNUSED)
{
    HB_BUFFER_ALLOCATE_VAR(buffer, khmer_category);

    /* We cannot setup masks here.  We save information about characters
     * and setup masks later on in a pause-callback. */

    unsigned int count = buffer->len;
    hb_glyph_info_t *info = buffer->info;
    for (unsigned int i = 0; i < count; i++)
        set_khmer_properties(info[i]);
}

static void
setup_syllables_khmer(const hb_ot_shape_plan_t *plan HB_UNUSED, hb_font_t *font HB_UNUSED, hb_buffer_t *buffer)
{
    find_syllables_khmer(buffer);
    foreach_syllable(buffer, start, end) buffer->unsafe_to_break(start, end);
}

/* Rules from:
 * https://docs.microsoft.com/en-us/typography/script-development/devanagari */

static void reorder_consonant_syllable(const hb_ot_shape_plan_t *plan,
                                       hb_face_t *face HB_UNUSED,
                                       hb_buffer_t *buffer,
                                       unsigned int start,
                                       unsigned int end)
{
    const khmer_shape_plan_t *khmer_plan = (const khmer_shape_plan_t *)plan->data;
    hb_glyph_info_t *info = buffer->info;

    /* Setup masks. */
    {
        /* Post-base */
        hb_mask_t mask = khmer_plan->mask_array[KHMER_BLWF] | khmer_plan->mask_array[KHMER_ABVF] |
                         khmer_plan->mask_array[KHMER_PSTF];
        for (unsigned int i = start + 1; i < end; i++)
            info[i].mask |= mask;
    }

    unsigned int num_coengs = 0;
    for (unsigned int i = start + 1; i < end; i++) {
        /* """
         * When a COENG + (Cons | IndV) combination are found (and subscript count
         * is less than two) the character combination is handled according to the
         * subscript type of the character following the COENG.
         *
         * ...
         *
         * Subscript Type 2 - The COENG + RO characters are reordered to immediately
         * before the base glyph. Then the COENG + RO characters are assigned to have
         * the 'pref' OpenType feature applied to them.
         * """
         */
        if (info[i].khmer_category() == OT_Coeng && num_coengs <= 2 && i + 1 < end) {
            num_coengs++;

            if (info[i + 1].khmer_category() == OT_Ra) {
                for (unsigned int j = 0; j < 2; j++)
                    info[i + j].mask |= khmer_plan->mask_array[KHMER_PREF];

                /* Move the Coeng,Ro sequence to the start. */
                buffer->merge_clusters(start, i + 2);
                hb_glyph_info_t t0 = info[i];
                hb_glyph_info_t t1 = info[i + 1];
                memmove(&info[start + 2], &info[start], (i - start) * sizeof(info[0]));
                info[start] = t0;
                info[start + 1] = t1;

                /* Mark the subsequent stuff with 'cfar'.  Used in Khmer.
                 * Read the feature spec.
                 * This allows distinguishing the following cases with MS Khmer fonts:
                 * U+1784,U+17D2,U+179A,U+17D2,U+1782
                 * U+1784,U+17D2,U+1782,U+17D2,U+179A
                 */
                if (khmer_plan->mask_array[KHMER_CFAR])
                    for (unsigned int j = i + 2; j < end; j++)
                        info[j].mask |= khmer_plan->mask_array[KHMER_CFAR];

                num_coengs = 2; /* Done. */
            }
        }

        /* Reorder left matra piece. */
        else if (info[i].khmer_category() == OT_VPre) {
            /* Move to the start. */
            buffer->merge_clusters(start, i + 1);
            hb_glyph_info_t t = info[i];
            memmove(&info[start + 1], &info[start], (i - start) * sizeof(info[0]));
            info[start] = t;
        }
    }
}

static void reorder_syllable_khmer(
    const hb_ot_shape_plan_t *plan, hb_face_t *face, hb_buffer_t *buffer, unsigned int start, unsigned int end)
{
    khmer_syllable_type_t syllable_type = (khmer_syllable_type_t)(buffer->info[start].syllable() & 0x0F);
    switch (syllable_type) {
    case khmer_broken_cluster: /* We already inserted dotted-circles, so just call the consonant_syllable. */
    case khmer_consonant_syllable:
        reorder_consonant_syllable(plan, face, buffer, start, end);
        break;

    case khmer_non_khmer_cluster:
        break;
    }
}

static inline void
insert_dotted_circles_khmer(const hb_ot_shape_plan_t *plan HB_UNUSED, hb_font_t *font, hb_buffer_t *buffer)
{
    if (unlikely(buffer->flags & HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE))
        return;

    /* Note: This loop is extra overhead, but should not be measurable.
     * TODO Use a buffer scratch flag to remove the loop. */
    bool has_broken_syllables = false;
    unsigned int count = buffer->len;
    hb_glyph_info_t *info = buffer->info;
    for (unsigned int i = 0; i < count; i++)
        if ((info[i].syllable() & 0x0F) == khmer_broken_cluster) {
            has_broken_syllables = true;
            break;
        }
    if (likely(!has_broken_syllables))
        return;

    hb_codepoint_t dottedcircle_glyph;
    if (!font->get_nominal_glyph(0x25CCu, &dottedcircle_glyph))
        return;

    hb_glyph_info_t dottedcircle = {0};
    dottedcircle.codepoint = 0x25CCu;
    set_khmer_properties(dottedcircle);
    dottedcircle.codepoint = dottedcircle_glyph;

    buffer->clear_output();

    buffer->idx = 0;
    unsigned int last_syllable = 0;
    while (buffer->idx < buffer->len && buffer->successful) {
        unsigned int syllable = buffer->cur().syllable();
        khmer_syllable_type_t syllable_type = (khmer_syllable_type_t)(syllable & 0x0F);
        if (unlikely(last_syllable != syllable && syllable_type == khmer_broken_cluster)) {
            last_syllable = syllable;

            hb_glyph_info_t ginfo = dottedcircle;
            ginfo.cluster = buffer->cur().cluster;
            ginfo.mask = buffer->cur().mask;
            ginfo.syllable() = buffer->cur().syllable();

            /* Insert dottedcircle after possible Repha. */
            while (buffer->idx < buffer->len && buffer->successful && last_syllable == buffer->cur().syllable() &&
                   buffer->cur().khmer_category() == OT_Repha)
                buffer->next_glyph();

            buffer->output_info(ginfo);
        } else
            buffer->next_glyph();
    }
    buffer->swap_buffers();
}

static void reorder_khmer(const hb_ot_shape_plan_t *plan, hb_font_t *font, hb_buffer_t *buffer)
{
    insert_dotted_circles_khmer(plan, font, buffer);

    foreach_syllable(buffer, start, end) reorder_syllable_khmer(plan, font->face, buffer, start, end);

    HB_BUFFER_DEALLOCATE_VAR(buffer, khmer_category);
}

static bool
decompose_khmer(const hb_ot_shape_normalize_context_t *c, hb_codepoint_t ab, hb_codepoint_t *a, hb_codepoint_t *b)
{
    switch (ab) {
    /*
     * Decompose split matras that don't have Unicode decompositions.
     */

    /* Khmer */
    case 0x17BEu:
        *a = 0x17C1u;
        *b = 0x17BEu;
        return true;
    case 0x17BFu:
        *a = 0x17C1u;
        *b = 0x17BFu;
        return true;
    case 0x17C0u:
        *a = 0x17C1u;
        *b = 0x17C0u;
        return true;
    case 0x17C4u:
        *a = 0x17C1u;
        *b = 0x17C4u;
        return true;
    case 0x17C5u:
        *a = 0x17C1u;
        *b = 0x17C5u;
        return true;
    }

    return (bool)c->unicode->decompose(ab, a, b);
}

static bool
compose_khmer(const hb_ot_shape_normalize_context_t *c, hb_codepoint_t a, hb_codepoint_t b, hb_codepoint_t *ab)
{
    /* Avoid recomposing split matras. */
    if (HB_UNICODE_GENERAL_CATEGORY_IS_MARK(c->unicode->general_category(a)))
        return false;

    return (bool)c->unicode->compose(a, b, ab);
}

const hb_ot_complex_shaper_t _hb_ot_complex_shaper_khmer = {
    collect_features_khmer,
    override_features_khmer,
    data_create_khmer,
    data_destroy_khmer,
    nullptr, /* preprocess_text */
    nullptr, /* postprocess_glyphs */
    HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT,
    decompose_khmer,
    compose_khmer,
    setup_masks_khmer,
    HB_TAG_NONE, /* gpos_tag */
    nullptr,     /* reorder_marks */
    HB_OT_SHAPE_ZERO_WIDTH_MARKS_NONE,
    false, /* fallback_position */
};

#endif