The values used to adjust the position of a glyph or set of glyphs.
| xAdvance | The positional adjustment that affects the horizontal advance of the glyph. |
| xPlacement | The positional adjustment that affects the horizontal bearing X of the glyph. |
| yAdvance | The positional adjustment that affects the vertical advance of the glyph. |
| yPlacement | The positional adjustment that affectsthe horizontal bearing Y of the glyph. |
| GlyphValueRecord | Constructor for new glyph value record. |