harfbuzz_rs_now 2.2.1

A high-level interface to HarfBuzz, exposing its most important functionality in a safe manner using Rust.
Documentation 
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#include "hb-glyph-to-svg-path.h"
#include "hb-common.h"
#include "hb-draw.h"
#include "string.h"
#include "stdio.h"
#include "stdarg.h"

enum
{
  HB_SHAPE_DONT_STOP,
  HB_SHAPE_GSUB_PHASE,
  HB_SHAPE_GPOS_PHASE
};

struct user_data_t
{
  user_data_t(char *str_,
              unsigned size_,
              unsigned stop_at_ = 0,
              unsigned stop_phase_ = 0)
      : str(str_), size(size_), stop_at(stop_at_), stop_phase(stop_phase_)
  {
  }
  char *str = nullptr;
  unsigned size = 0;
  unsigned consumed = 0;
  hb_bool_t failure = false;
  unsigned stop_at = 0;
  unsigned stop_phase = 0;
  hb_bool_t stopping = false;
  unsigned current_phase = 0;
};

static void
_user_data_printf(user_data_t *data, const char *format, ...)
{
#define BUFSIZE 1000
  char buf[BUFSIZE];
  int len;
  va_list va;

  if (!data || data->failure)
    return;

  va_start(va, format);
  len = vsnprintf(buf, BUFSIZE, format, va);
  va_end(va);

  if (data->consumed + len >= data->size || len < 0 || len > BUFSIZE)
  {
    data->failure = true;
    return;
  }

  memcpy(data->str + data->consumed, buf, len);
  data->consumed += len;
#undef BUFSIZE
}

static void
move_to(hb_draw_funcs_t *dfuncs, user_data_t *draw_data, hb_draw_state_t *,
        float to_x, float to_y,
        void *)
{
  _user_data_printf(draw_data, "M%g,%g", (double)to_x, (double)to_y);
}

static void
line_to(hb_draw_funcs_t *dfuncs, user_data_t *draw_data, hb_draw_state_t *,
        float to_x, float to_y,
        void *)
{
  _user_data_printf(draw_data, "L%g,%g", (double)to_x, (double)to_y);
}

static void
quadratic_to(hb_draw_funcs_t *dfuncs, user_data_t *draw_data, hb_draw_state_t *,
             float control_x, float control_y,
             float to_x, float to_y,
             void *)
{
  _user_data_printf(draw_data, "Q%g,%g %g,%g",
                    (double)control_x,
                    (double)control_y,
                    (double)to_x,
                    (double)to_y);
}

static void
cubic_to(hb_draw_funcs_t *dfuncs, user_data_t *draw_data, hb_draw_state_t *,
         float control1_x, float control1_y,
         float control2_x, float control2_y,
         float to_x, float to_y,
         void *)
{
  _user_data_printf(draw_data, "C%g,%g %g,%g %g,%g",
                    (double)control1_x,
                    (double)control1_y,
                    (double)control2_x,
                    (double)control2_y,
                    (double)to_x,
                    (double)to_y);
}

static void
close_path(hb_draw_funcs_t *dfuncs, user_data_t *draw_data, hb_draw_state_t *, void *)
{
  _user_data_printf(draw_data, "Z");
}

static hb_draw_funcs_t *funcs = 0;

extern "C"
{
  int hb_glyph_to_svg_path(hb_font_t *font, hb_codepoint_t glyph, char *buf, unsigned buf_size)
  {
    if (funcs == 0) /* not the best pattern for multi-threaded apps which is not a concern here */
    {
      funcs = hb_draw_funcs_create(); /* will be leaked */
      hb_draw_funcs_set_move_to_func(funcs, (hb_draw_move_to_func_t)move_to, nullptr, nullptr);
      hb_draw_funcs_set_line_to_func(funcs, (hb_draw_line_to_func_t)line_to, nullptr, nullptr);
      hb_draw_funcs_set_quadratic_to_func(funcs, (hb_draw_quadratic_to_func_t)quadratic_to, nullptr, nullptr);
      hb_draw_funcs_set_cubic_to_func(funcs, (hb_draw_cubic_to_func_t)cubic_to, nullptr, nullptr);
      hb_draw_funcs_set_close_path_func(funcs, (hb_draw_close_path_func_t)close_path, nullptr, nullptr);
    }

    user_data_t draw_data(buf, buf_size);
    hb_font_draw_glyph(font, glyph, funcs, &draw_data);
    if (draw_data.failure)
      return -1;

    buf[draw_data.consumed] = '\0';
    return draw_data.consumed;
  }
}