pango pango_context_get_language

// Returns the approximate number of characters that can horizontally fit in
// |pixel_width| pixels.
int GetCharacterWidthForPixels(GtkWidget* widget, int pixel_width) {
  DCHECK(gtk_widget_get_realized(widget))
      << " widget must be realized to compute font metrics correctly";

  PangoContext* context = gtk_widget_create_pango_context(widget);

  GtkStyle* style = gtk_widget_get_style(widget);

  PangoFontMetrics* metrics = pango_context_get_metrics(
      context,
      style->font_desc,
      pango_context_get_language(context)); <======

  // This technique (max of char and digit widths) matches the code in
  // gtklabel.c.
  int char_width = pixel_width * PANGO_SCALE /
      std::max(pango_font_metrics_get_approximate_char_width(metrics),
               pango_font_metrics_get_approximate_digit_width(metrics));

  pango_font_metrics_unref(metrics);
  g_object_unref(context);

  return char_width;
}

chromium/gtk_util.cc at master · trevorlinton/chromium · GitHub