<summary> Offset in the advance direction of the run. A positive advance offset moves the glyph to the right (in pre-transform coordinates) if the run is left-to-right or to the left if the run is right-to-left. </summary>
<summary> Offset in the ascent direction, i.e., the direction ascenders point. A positive ascender offset moves the glyph up (in pre-transform coordinates). </summary>
<summary> Optional adjustment to a glyph's position. A glyph offset changes the position of a glyph without affecting the pen position. Offsets are in logical, pre-transform units. </summary>