2007-12-10  Behdad Esfahbod  <behdad@gnome.org>

        Bug 478914 – Use something invalid instead of '?' when validating
        input text

        * pango/pango-layout.c (pango_layout_set_text): Set invalid input
        bytes to -1, which gives a unichar value of -1, and eventually a
        glyph value of -1, aka PANGO_GLYPH_INVALID_INPUT.

        * pango/fonts.c (pango_font_get_glyph_extents),
        (pango_font_get_metrics), (pango_font_get_font_map):
        * pango/modules.c (build_map):
        * pango/pango-context.c (get_script), (get_shaper_and_font),
        (string_from_script), (itemize_state_process_run):
        * pango/pango-coverage.c (pango_coverage_get):
        * pango/pango-impl-utils.h:
        * pango/pango-utils.c:
        * pango/pangocairo-font.c (pango_cairo_font_get_scaled_font),
        (_pango_cairo_font_private_get_hex_box_info),
        (_pango_cairo_font_private_get_glyph_extents_missing):
  ...