# HHistDirection [Integration guide](https://docs.lumencharts.com/charting-library/reference/compatibility) · [Reference index](https://docs.lumencharts.com/charting-library/api/) Public contract reference. This declaration describes types and callback shapes; availability is constrained by the linked integration guide and the runtime capability. Legacy product-specific fields are not a promise of implementation. ```ts declare enum HHistDirection { LeftToRight = "left_to_right", RightToLeft = "right_to_left", } ``` --- Documentation page: https://docs.lumencharts.com/charting-library/api/HHistDirection