/**
 * Pure, worklet-safe clustering for reference-line grouping — collapse Form-A
 * lines whose value-Y positions sit near each other into one count handle. Free of
 * hooks / SharedValues so it unit-tests without Reanimated; the per-frame call +
 * rendering live in the controller / `ReferenceLineGroupOverlay`.
 */
/** One collapsed cluster of nearby reference lines. */
export interface ReferenceGroup {
    /** Centroid Y (canvas px) of the cluster — where the count handle is drawn. */
    cy: number;
    /** Number of lines collapsed into the cluster (≥ 2). */
    count: number;
}
/** Result of clustering a frame's reference-line Y positions. */
export interface ReferenceGrouping {
    /**
     * Index-aligned with the input Ys: `true` when this line's individual tag is
     * collapsed into a cluster (a multi-line group) and should be suppressed.
     */
    hidden: boolean[];
    /** One entry per multi-line cluster (singletons render normally, never here). */
    groups: ReferenceGroup[];
}
/**
 * Single-linkage cluster of reference-line handle Ys: lines whose sorted Y gaps are
 * all `<= radius` chain into one group. Entries `< 0` (not a Form-A line / off the
 * canvas) are ignored. Returns which lines are collapsed (`hidden`) plus a centroid
 * + count per multi-line cluster. A non-positive `radius` disables grouping.
 */
export declare function groupReferenceLines(ys: number[], radius: number): ReferenceGrouping;
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