static PangoFontMetrics *
pango_cairo_core_text_font_create_base_metrics_for_context (PangoCairoFont *font,
                                                            PangoContext   *context)
{
  PangoCoreTextFont *cfont = (PangoCoreTextFont *) font;
  PangoFontMetrics *metrics;
  PangoFontDescription *font_desc;
  PangoLayout *layout;
  PangoRectangle extents;
  PangoLanguage *language = pango_context_get_language (context);
  const char *sample_str = pango_language_get_sample_string (language);
  CTFontRef ctfont;

  metrics = pango_font_metrics_new ();

  ctfont = pango_core_text_font_get_ctfont (cfont);

  metrics->ascent = CTFontGetAscent (ctfont) * PANGO_SCALE;
  metrics->descent = CTFontGetDescent (ctfont) * PANGO_SCALE;

  metrics->underline_position = CTFontGetUnderlinePosition (ctfont) * PANGO_SCALE;
  metrics->underline_thickness = CTFontGetUnderlineThickness (ctfont) * PANGO_SCALE;

  metrics->strikethrough_position = metrics->ascent / 3;
  metrics->strikethrough_thickness = CTFontGetUnderlineThickness (ctfont) * PANGO_SCALE;

  layout = pango_layout_new (context);
  font_desc = pango_font_describe_with_absolute_size ((PangoFont *) font);
  pango_layout_set_font_description (layout, font_desc);
  pango_layout_set_text (layout, sample_str, -1);
  pango_layout_get_extents (layout, NULL, &extents);

  metrics->approximate_char_width = extents.width / pango_utf8_strwidth (sample_str);

  pango_layout_set_text (layout, "0123456789", -1);
  metrics->approximate_digit_width = max_glyph_width (layout);

  pango_font_description_free (font_desc);
  g_object_unref (layout);

  return metrics;
}
PangoFontMetrics *
_pango_cairo_font_get_metrics (PangoFont     *font,
			       PangoLanguage *language)
{
  PangoCairoFont *cfont = (PangoCairoFont *) font;
  PangoCairoFontPrivate *cf_priv = PANGO_CAIRO_FONT_PRIVATE (font);
  PangoCairoFontMetricsInfo *info = NULL; /* Quiet gcc */
  GSList *tmp_list;

  const char *sample_str = pango_language_get_sample_string (language);

  tmp_list = cf_priv->metrics_by_lang;
  while (tmp_list)
    {
      info = tmp_list->data;

      if (info->sample_str == sample_str)    /* We _don't_ need strcmp */
	break;

      tmp_list = tmp_list->next;
    }

  if (!tmp_list)
    {
      PangoFontMap *fontmap;
      PangoContext *context;
      cairo_font_options_t *font_options;
      PangoLayout *layout;
      PangoRectangle extents;
      PangoFontDescription *desc;
      cairo_scaled_font_t *scaled_font;
      cairo_matrix_t cairo_matrix;
      PangoMatrix pango_matrix;
      PangoMatrix identity = PANGO_MATRIX_INIT;

      int height, shift;

      /* XXX this is racy.  need a ref'ing getter... */
      fontmap = pango_font_get_font_map (font);
      if (!fontmap)
        return pango_font_metrics_new ();
      fontmap = g_object_ref (fontmap);

      info = g_slice_new0 (PangoCairoFontMetricsInfo);

      cf_priv->metrics_by_lang = g_slist_prepend (cf_priv->metrics_by_lang, info);

      info->sample_str = sample_str;

      scaled_font = _pango_cairo_font_private_get_scaled_font (cf_priv);

      context = pango_font_map_create_context (fontmap);
      pango_context_set_language (context, language);

      font_options = cairo_font_options_create ();
      cairo_scaled_font_get_font_options (scaled_font, font_options);
      pango_cairo_context_set_font_options (context, font_options);
      cairo_font_options_destroy (font_options);

      info->metrics = (* PANGO_CAIRO_FONT_GET_IFACE (font)->create_base_metrics_for_context) (cfont, context);

      /* We now need to adjust the base metrics for ctm */
      cairo_scaled_font_get_ctm (scaled_font, &cairo_matrix);
      pango_matrix.xx = cairo_matrix.xx;
      pango_matrix.yx = cairo_matrix.yx;
      pango_matrix.xy = cairo_matrix.xy;
      pango_matrix.yy = cairo_matrix.yy;
      pango_matrix.x0 = 0;
      pango_matrix.y0 = 0;
      if (G_UNLIKELY (0 != memcmp (&identity, &pango_matrix, 4 * sizeof (double))))
        {
	  double xscale = pango_matrix_get_font_scale_factor (&pango_matrix);
	  if (xscale) xscale = 1 / xscale;

	  info->metrics->ascent *= xscale;
	  info->metrics->descent *= xscale;
	  info->metrics->underline_position *= xscale;
	  info->metrics->underline_thickness *= xscale;
	  info->metrics->strikethrough_position *= xscale;
	  info->metrics->strikethrough_thickness *= xscale;
	}


      /* Set the matrix on the context so we don't have to adjust the derived
       * metrics. */
      pango_context_set_matrix (context, &pango_matrix);

      /* Update approximate_*_width now */
      layout = pango_layout_new (context);
      desc = pango_font_describe_with_absolute_size (font);
      pango_layout_set_font_description (layout, desc);
      pango_font_description_free (desc);

      pango_layout_set_text (layout, sample_str, -1);
      pango_layout_get_extents (layout, NULL, &extents);

      info->metrics->approximate_char_width = extents.width / pango_utf8_strwidth (sample_str);

      pango_layout_set_text (layout, "0123456789", -1);
      info->metrics->approximate_digit_width = max_glyph_width (layout);

      g_object_unref (layout);


      /* We may actually reuse ascent/descent we got from cairo here.  that's
       * in cf_priv->font_extents.
       */
      height = info->metrics->ascent + info->metrics->descent;
      switch (cf_priv->gravity)
	{
	  default:
	  case PANGO_GRAVITY_AUTO:
	  case PANGO_GRAVITY_SOUTH:
	    break;
	  case PANGO_GRAVITY_NORTH:
	    info->metrics->ascent = info->metrics->descent;
	    break;
	  case PANGO_GRAVITY_EAST:
	  case PANGO_GRAVITY_WEST:
	    {
	      int ascent = height / 2;
	      if (cf_priv->is_hinted)
	        ascent = PANGO_UNITS_ROUND (ascent);
	      info->metrics->ascent = ascent;
	    }
	}
      shift = (height - info->metrics->ascent) - info->metrics->descent;
      info->metrics->descent += shift;
      info->metrics->underline_position -= shift;
      info->metrics->strikethrough_position -= shift;
      info->metrics->ascent = height - info->metrics->descent;

      g_object_unref (context);
      g_object_unref (fontmap);
    }

  return pango_font_metrics_ref (info->metrics);
}