/**
 * Utility functions for ToolbarControl overflow calculation.
 *
 * @packageDocumentation
 */
/**
 * Calculates the first item index that should collapse into an overflow menu.
 *
 * Uses a two-pass algorithm:
 * 1. Check whether all items fit without an overflow button.
 * 2. If they don't, re-fit as many items as possible while reserving space for the overflow button.
 *
 * Returns `itemCount` when all items fit (no overflow).
 *
 * @param itemCount - Total number of toolbar items.
 * @param containerSize - Available size of the toolbar container (width for horizontal, height for vertical).
 * @param itemSizes - Measured sizes of each toolbar item along the same axis. Must have `itemCount` entries.
 * @param overflowButtonSize - Size of the overflow button that appears when overflow occurs.
 * @returns The index of the first item that moves to the overflow menu, or `itemCount` when there is no overflow.
 * @internal
 */
export declare function calculateOverflowStartIndex(itemCount: number, containerSize: number, itemSizes: number[], overflowButtonSize: number): number;