import type { RefObject } from "react";
/**
 * The measuring half of progressive overflow — `chooseVisibleCount`
 * is the decision, this is the tape measure.
 *
 * ## Measured, not breakpointed
 *
 * mux-magic collapses at a hardcoded `480px` and plex-channels at a
 * hardcoded `760px`, and both numbers are wrong the moment a label
 * gets longer, the density axis changes, or a rail takes half the
 * row. A measured bar has no number to be wrong: it asks the
 * elements how wide they actually are, in the font and density they
 * are actually rendered in.
 *
 * ## One instance, and cached widths
 *
 * An item that has collapsed is **not in the DOM** — that is the
 * whole point, against a mechanism that renders every action twice
 * and hides one with a CSS specificity coin-flip. So its width
 * cannot be re-read while it is away, and it is remembered from
 * when it was last in the bar instead.
 *
 * The first paint is what seeds the cache: every item starts in the
 * bar (`chooseVisibleCount` returns all of them for an unmeasured
 * container), gets measured, and the row collapses **before paint**
 * because the measuring runs in a layout effect. Any item whose
 * width is still unknown forces one more all-visible pass rather
 * than being guessed at — one extra layout pass, and it converges,
 * because a mounted item always measures.
 *
 * ⚠️ **The measured element must not be sized by its own contents.**
 * If the bar shrink-wraps its items, collapsing one narrows the box,
 * which collapses another — a loop with no error anywhere.
 * `Toolbar`'s root is `flex-1 min-w-0` for exactly this reason, the
 * same trap `useAdaptiveColumns` documents about a container capped
 * by its own answer.
 */
export declare const useToolbarOverflow: ({ itemKeys, }: {
    /** Priority order, highest first. */
    itemKeys: readonly string[];
}) => {
    containerRef: RefObject<HTMLDivElement | null>;
    /** Callback ref for each item's box. `null` on unmount. */
    trackItem: (key: string, element: HTMLElement | null) => void;
    /** Callback ref for the overflow trigger's box. */
    trackTrigger: (element: HTMLElement | null) => void;
    visibleCount: number;
};
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