sile 0.14.8

Simon’s Improved Layout Engine
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#include <hb.h>

#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>

#include "hb-utils.h"


int get_typographic_extents (lua_State *L) {
  double upem;
  double ascender;
  double descender;
  double x_height;

  hb_font_t* hbFont = get_hb_font(L, 1);
  hb_font_extents_t metrics = {0,0,0};
  upem = hb_face_get_upem(hb_font_get_face(hbFont));
  hb_font_get_h_extents(hbFont, &metrics);
  ascender = metrics.ascender / upem;
  descender = -metrics.descender / upem;

  lua_newtable(L);
  lua_pushstring(L, "ascender");
  lua_pushnumber(L, ascender);
  lua_settable(L, -3);
  lua_pushstring(L, "x_height");
  lua_pushnumber(L, x_height);
  lua_settable(L, -3);
  lua_pushstring(L, "descender");
  lua_pushnumber(L, descender);
  lua_settable(L, -3);

  return 1;
}


int glyphwidth (lua_State* L) {
  size_t font_l;
  unsigned int gid = luaL_checknumber(L, 1);
  hb_font_t* hbFont = get_hb_font(L, 2);
  double upem = hb_face_get_upem(hb_font_get_face(hbFont));
  hb_position_t width = hb_font_get_glyph_h_advance(hbFont, gid);
  lua_pushnumber(L, width / upem);
  return 1;
}

#if !defined LUA_VERSION_NUM
/* Lua 5.0 */
#define luaL_Reg luaL_reg
#endif

#if !defined LUA_VERSION_NUM || LUA_VERSION_NUM==501
/*
** Adapted from Lua 5.2.0
*/
void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup) {
  luaL_checkstack(L, nup+1, "too many upvalues");
  for (; l->name != NULL; l++) {  /* fill the table with given functions */
    int i;
    lua_pushstring(L, l->name);
    for (i = 0; i < nup; i++)  /* copy upvalues to the top */
      lua_pushvalue(L, -(nup+1));
    lua_pushcclosure(L, l->func, nup);  /* closure with those upvalues */
    lua_settable(L, -(nup + 3));
  }
  lua_pop(L, nup);  /* remove upvalues */
}
#endif

static const struct luaL_Reg lib_table [] = {
  {"get_typographic_extents", get_typographic_extents},
  {"glyphwidth", glyphwidth},
  {NULL, NULL}
};

int luaopen_fontmetrics (lua_State *L) {
  lua_newtable(L);
  luaL_setfuncs(L, lib_table, 0);
  return 1;
}