A MarkPositionAdjustment defines the positional adjustment of a glyph relative to the anchor point of base glyph.
This data structure is used by the Mark-to-Base, Mark-to-Mark, and Mark-to-Ligature OpenType font features.
| xPositionAdjustment | The horizontal positional adjustment of the glyph relative to the anchor point of its parent base glyph. | 
| yPositionAdjustment | The vertical positional adjustment of the glyph relative to the anchor point of its parent base glyph. | 
| MarkPositionAdjustment | Initializes and returns an instance of MarkPositionAdjustment. |