test.c

/* Based on: https://github.com/harfbuzz/harfbuzz-tutorial/blob/master/hello-harfbuzz-opentype.c */

#include <stdio.h>
#include <math.h>

#include <hb.h>
#include <hb-ot.h>

#define FONT_SIZE 36
#define MARGIN (FONT_SIZE * .5)

/* Use native open type implementation to load font
  https://github.com/harfbuzz/harfbuzz/issues/255 */
hb_font_t*
get_font_ot(const char *filename, int size)
{
  FILE* file = fopen(filename, "rb");
  fseek(file, 0, SEEK_END);
  unsigned int length = ftell(file);
  fseek(file, 0, SEEK_SET);

  char* data = malloc(length);
  fread(data, length, 1, file);
  fclose(file);

  hb_blob_t* blob = hb_blob_create(data, length, HB_MEMORY_MODE_WRITABLE, (void*)data, NULL);
  hb_face_t* face = hb_face_create(blob, 0);
  hb_font_t* font = hb_font_create(face);

  hb_ot_font_set_funcs(font);
  hb_font_set_scale(font, size, size);

  return font;
}

int
main(int argc, char **argv)
{
  const char *fontfile;
  const char *text;

  if (argc < 3)
  {
    fprintf (stderr, "usage: hello-harfbuzz font-file.ttf text\n");
    exit (1);
  }

  fontfile = argv[1];
  text = argv[2];

  /* Create hb-ft font. */
  hb_font_t *hb_font;
  hb_font = get_font_ot (fontfile, FONT_SIZE*64);

  /* Create hb-buffer and populate. */
  hb_buffer_t *hb_buffer;
  hb_buffer = hb_buffer_create ();
  hb_buffer_add_utf8 (hb_buffer, text, -1, 0, -1);
  hb_buffer_guess_segment_properties (hb_buffer);

  /* Shape it! */
  hb_shape (hb_font, hb_buffer, NULL, 0);

  /* Get glyph information and positions out of the buffer. */
  unsigned int len = hb_buffer_get_length (hb_buffer);
  hb_glyph_info_t *info = hb_buffer_get_glyph_infos (hb_buffer, NULL);
  hb_glyph_position_t *pos = hb_buffer_get_glyph_positions (hb_buffer, NULL);

  /* Print them out as is. */
  printf ("Raw buffer contents:\n");
  for (unsigned int i = 0; i < len; i++)
  {
    hb_codepoint_t gid   = info[i].codepoint;
    unsigned int cluster = info[i].cluster;
    double x_advance = pos[i].x_advance / 64.;
    double y_advance = pos[i].y_advance / 64.;
    double x_offset  = pos[i].x_offset / 64.;
    double y_offset  = pos[i].y_offset / 64.;

    char glyphname[32];
    hb_font_get_glyph_name (hb_font, gid, glyphname, sizeof (glyphname));

    printf ("glyph='%s'	cluster=%d	advance=(%g,%g)	offset=(%g,%g)\n",
            glyphname, cluster, x_advance, y_advance, x_offset, y_offset);
  }

  printf ("Converted to absolute positions:\n");
  /* And converted to absolute positions. */
  {
    double current_x = 0;
    double current_y = 0;
    for (unsigned int i = 0; i < len; i++)
    {
      hb_codepoint_t gid   = info[i].codepoint;
      unsigned int cluster = info[i].cluster;
      double x_position = current_x + pos[i].x_offset / 64.;
      double y_position = current_y + pos[i].y_offset / 64.;


      char glyphname[32];
      hb_font_get_glyph_name (hb_font, gid, glyphname, sizeof (glyphname));

      printf ("glyph='%s'	cluster=%d	position=(%g,%g)\n",
	      glyphname, cluster, x_position, y_position);

      current_x += pos[i].x_advance / 64.;
      current_y += pos[i].y_advance / 64.;
    }
  }

  hb_buffer_destroy (hb_buffer);
  hb_font_destroy (hb_font);

  return 0;
}