Interface LinearScaleMapper

src/scale/scaleMapper.ts:384–399

* Generally, no need to export `LinearScaleMapper` and not recommended * to visit `_extent` directly outside, otherwise it may be incorrect * due to possible polymorphism - use `getExtentUnsafe()` instead.

 * due to possible polymorphism - use `getExtentUnsafe()` instead.
 */
interface LinearScaleMapper extends ScaleMapper {
    /**
     * [CAVEAT]:
     *  - Should update only by `setExtent` or `setExtent2`!
     *  - The caller of `setExtent()` should ensure `extent[0] <= extent[1]`,
     *    but it is initialized as `[Infinity, -Infinity]`.
     *    With these restriction, `extent` can only be either:
     *      + `extent[0] < extent[1]` and both finite, or
     *      + `extent[0] === extent[1]` and both finite, or
     *      + `extent[0] === Infinity && extent[1] === -Infinity`
     *
     * Structure: `_extent[ScaleExtentKind][]`
     */
    readonly _extents: number[][];
    readonly _frozen: boolean;
}

export function initLinearScaleMapper(
    // If input `null/undefined`, a mapper will be created.