hb.c

#include <X11/Xft/Xft.h>
#include <X11/cursorfont.h>
#include <hb-ft.h>
#include <hb.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

/* We turn off clang-format because suckless can't handle circural dependencies */
/* clang-format off */
#include "st.h"
#include "hb.h"
/* clang-format on */

#define FEATURE(c1, c2, c3, c4)                                                                                           \
        {                                                                                                                 \
                .tag = HB_TAG(c1, c2, c3, c4), .value = 1, .start = HB_FEATURE_GLOBAL_START, .end = HB_FEATURE_GLOBAL_END \
        }
#define BUFFER_STEP 256

static hb_font_t *hbfindfont(XftFont *match);

typedef struct {
        XftFont *match;
        hb_font_t *font;
} HbFontMatch;

typedef struct {
        size_t capacity;
        HbFontMatch *fonts;
} HbFontCache;

static HbFontCache hbfontcache = { 0, NULL };

typedef struct {
        size_t capacity;
        Rune *runes;
} RuneBuffer;

static RuneBuffer hbrunebuffer = { 0, NULL };

/*
 * Poplulate the array with a list of font features, wrapped in FEATURE macro,
 * e. g.
 * FEATURE('c', 'a', 'l', 't'), FEATURE('d', 'l', 'i', 'g')
 */
static hb_feature_t features[] = { FEATURE('c', 'a', 'l', 't'), FEATURE('d', 'l', 'i', 'g') };

void hbunloadfonts(void)
{
        for (size_t i = 0; i < hbfontcache.capacity; i++) {
                hb_font_destroy(hbfontcache.fonts[i].font);
                XftUnlockFace(hbfontcache.fonts[i].match);
        }

        free(hbfontcache.fonts);
        hbfontcache.fonts = NULL;
        hbfontcache.capacity = 0;
}

hb_font_t *hbfindfont(XftFont *match)
{
        for (size_t i = 0; i < hbfontcache.capacity; i++) {
                if (hbfontcache.fonts[i].match == match)
                        return hbfontcache.fonts[i].font;
        }

        /* Font not found in cache, caching it now. */
        hbfontcache.fonts = (HbFontMatch *)realloc(hbfontcache.fonts, sizeof(HbFontMatch) * (hbfontcache.capacity + 1));
        if (hbfontcache.fonts == NULL)
                die("Failed to realloc HbFontCache fonts.");
        FT_Face face = XftLockFace(match);
        hb_font_t *font = hb_ft_font_create(face, NULL);
        if (font == NULL)
                die("Failed to load Harfbuzz font.");

        hbfontcache.fonts[hbfontcache.capacity].match = match;
        hbfontcache.fonts[hbfontcache.capacity].font = font;
        hbfontcache.capacity += 1;

        return font;
}

void hbtransform(HbTransformData *data, XftFont *xfont, Glyph const *glyphs, int start, int length)
{
        ushort mode = USHRT_MAX;
        unsigned int glyph_count;
        int rune_idx;
        int glyph_idx;
        int end = start + length;

        hb_font_t *font = hbfindfont(xfont);
        if (font == NULL)
                return;

        hb_buffer_t *buffer = hb_buffer_create();
        hb_buffer_set_direction(buffer, HB_DIRECTION_LTR);
        hb_buffer_set_cluster_level(buffer, HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS);

        /* Resize the buffer if required length is larger. */
        if (hbrunebuffer.capacity < (size_t)length) {
                hbrunebuffer.capacity = ((long)length / BUFFER_STEP + 1) * BUFFER_STEP;
                hbrunebuffer.runes = (Rune *)realloc(hbrunebuffer.runes, hbrunebuffer.capacity * sizeof(Rune));
                if (hbrunebuffer.runes == NULL)
                        die("Failed to realloc RuneBuffer runes.");
        }

        /* Fill buffer with codepoints. */
        for (rune_idx = 0, glyph_idx = start; glyph_idx < end; glyph_idx++, rune_idx++) {
                hbrunebuffer.runes[rune_idx] = glyphs[glyph_idx].u;
                mode = glyphs[glyph_idx].mode;
                if (mode & ATTR_WDUMMY)
                        hbrunebuffer.runes[rune_idx] = 0x0020;
        }
        hb_buffer_add_codepoints(buffer, hbrunebuffer.runes, length, 0, length);

        /* Shape the segment. */
        hb_shape(font, buffer, features, sizeof(features) / sizeof(hb_feature_t));

        /* Get new glyph info. */
        hb_glyph_info_t *info = hb_buffer_get_glyph_infos(buffer, &glyph_count);
        hb_glyph_position_t *pos = hb_buffer_get_glyph_positions(buffer, &glyph_count);

        /* Fill the output. */
        data->buffer = buffer;
        data->glyphs = info;
        data->positions = pos;
        data->count = glyph_count;
}

void hbcleanup(HbTransformData *data)
{
        hb_buffer_destroy(data->buffer);
        memset(data, 0, sizeof(HbTransformData));
}