PangoGlyph pango_ft2_get_unknown_glyph ( PangoFont* font )
Return the index of a glyph suitable for drawing unknown
PANGO_GLYPH_EMPTY if no suitable
If you want to draw an unknown-box for a character that is not covered by the font, use PANGO_GET_UNKNOWN_GLYPH() instead.
The data is owned by the caller of the function.