Test code for caret offset calculation using Harfbuzz, Icu and Freetype.

test_harfbuzz.cpp

#include <stdio.h>
#include <stdlib.h>
#include <ft2build.h>
#include FT_FREETYPE_H
#include <harfbuzz/hb.h>
#include <harfbuzz/hb-ft.h>
#include <unicode/uchriter.h>
#include <unicode/schriter.h>
#include <unicode/ustring.h>
#include <unicode/ustdio.h>
#include <unicode/brkiter.h>
#include <string>

/* ------------------------------------------------------------- */

struct Font {
  FT_Face face;
  hb_font_t* hb_font;
  hb_buffer_t* hb_buffer;
  hb_glyph_info_t* glyph_info;
  hb_glyph_position_t* glyph_pos;
  unsigned int glyph_count;
};


FT_Library library = NULL;

/* ------------------------------------------------------------- */

int main() {

  /* Harfbuzz + Freetype vars. */
  std::string test_string = "Af̀fiZ";
  std::string fontfile;
  int r = 0;
  unsigned int i = 0;
  FT_Error err;
  Font font;

  /* ICU */
  UBreakIterator* bi = NULL;
  int32_t p = 0;
  UErrorCode icu_err = U_ZERO_ERROR;
  UnicodeString ts(test_string.c_str());
  const UChar* ts_ptr = ts.getTerminatedBuffer();
 
  printf("\n\n");
  printf("Testing caret offset calculation with Freetype + Harfbuzz.\n");
  printf("\n\n");

  /* Initialize + load. */
  font.face = NULL;
  font.hb_font = NULL;
  font.hb_buffer = NULL;
  font.glyph_info = NULL;
  font.glyph_pos = NULL;
  font.glyph_count = 0;

  err = FT_Init_FreeType(&library);
  if (FT_Err_Ok != err) {
    printf("Failed to initialize Freetype.");
    return -1;
  }
  
  fontfile = "data/Clarendon.ttf";
  err = FT_New_Face(library, fontfile.c_str(), 0, &font.face);
  
  if (FT_Err_Ok != err) {
    printf("Failed to create a new ft face.");
    r = -1;
    goto error;
  }

  font.hb_font = hb_ft_font_create(font.face, 0);
  if (NULL == font.hb_font) {
    printf("Failed to create harfbuzz font context.");
    r = -2;
    goto error;
  }

  font.hb_buffer = hb_buffer_create();
  if (NULL == font.hb_buffer) {
    printf("Failed to create the harfbuzz buffer.");
    r = -3;
    goto error;
  }

  /* Write some content. */
  hb_buffer_set_direction(font.hb_buffer, HB_DIRECTION_LTR);
  hb_buffer_set_script(font.hb_buffer, HB_SCRIPT_UNKNOWN);
  hb_buffer_add_utf8(font.hb_buffer, test_string.c_str(), test_string.size(), 0, test_string.size());
  hb_shape(font.hb_font, font.hb_buffer, NULL, 0);

  font.glyph_count = hb_buffer_get_length(font.hb_buffer);
  font.glyph_info = hb_buffer_get_glyph_infos(font.hb_buffer, NULL);
  font.glyph_pos = hb_buffer_get_glyph_positions(font.hb_buffer, NULL);

  /* Iterate over HB glyphs */
  for (i = 0; i < font.glyph_count; ++i) {
    printf("Glyph: %u, cluster: %d\n", i, font.glyph_info[i].cluster);
  }

  /* Interate over graphmemes. */
  bi = ubrk_open(UBRK_CHARACTER, 0, ts_ptr, u_strlen(ts_ptr), &icu_err);
  if (U_FAILURE(icu_err)) {
    printf("Error: failed to create a break iterator.");
    r = -4;
    goto error;
  }
    
  p = ubrk_first(bi);

  printf("\n");
  while (p != UBRK_DONE) {
    printf("Graphmeme offset: %u\n", p);
    p = ubrk_next(bi);
  }
    
  ubrk_close(bi);

  printf("\n\n");

 error:
  if (NULL != font.hb_buffer) {
    hb_buffer_destroy(font.hb_buffer);
    font.hb_buffer = NULL;
  }
  
  if (NULL != font.hb_font) {
    hb_font_destroy(font.hb_font);
    font.hb_font = NULL;
  }

  if (NULL != font.face) {
    err = FT_Done_Face(font.face);
    if (FT_Err_Ok != err) {
      printf("Failed FT_Done_Face.");
    }
    font.face = NULL;
  }
  
  return r;
     

}