message: OpenType: GPOS Mark-to-Mark Attachment
diff: @@ -1476,6 +1476,16 @@ let mark_to_ligature_attachment = (
  }
  );
  +/// # GPOS Lookup Type 6: Mark-to-Mark Attachment Positioning Subtable
  +///
  +/// The MarkToMark attachment (MarkMarkPos) subtable is identical in form to the MarkToBase
  +/// attachment subtable, although its function is different.
  +///
  +/// ## References
  +///
  +/// - [Microsoft's OpenType Spec: GPOS Lookup Type 6](https://docs.microsoft.com/en-us/typography/opentype/spec/gpos#lookup-type-6-mark-to-mark-attachment-positioning-subtable)
  +let mark_to_mark_attachment = mark_to_base_attachment;
  +
  /// # Lookup table
  ///
  /// ## References
  @@ -1503,6 +1513,7 @@ let lookup_table = fun (tag : U32) => (
  3 => cursive_attachment,
  4 => mark_to_base_attachment,
  5 => mark_to_ligature_attachment,
  + 6 => mark_to_mark_attachment,
  _ => unknown_table,
  },
  _ => fail,
  