PangoGlyphUnit:
PangoGlyphGeometry: @width: the logical width to use for the the character. @x_offset: horizontal offset from nominal character position. @y_offset: vertical offset from nominal character position.
PangoGlyphInfo: @glyph: the glyph itself. @geometry: the positional information about the glyph. @attr: the visual attributes of the glyph.
PangoGlyphString:
PangoGlyphVisAttr: @is_cluster_start: set for the first logical glyph in each cluster. (Clusters are stored in visual order, within the cluster, glyphs are always ordered in logical order, since visual order is meaningless; that is, in Arabic text, accent glyphs follow the glyphs for the base character.)