/** A cell's address in a matrix: its row, then its place along the row. */
export interface MatrixAt {
    row: number;
    col: number;
}
/**
 * WHERE A KEY MOVES INSIDE A MATRIX. This is the WAI-ARIA grid model over rows of their own lengths: a
 * wallboard's lanes end early, and a step onto a shorter row lands on its last cell. Moves stop at the
 * edges rather than wrapping. Ctrl+Home and Ctrl+End reach the first and the last cell. `null` means the
 * key is not a grid key, so the caller must not preventDefault it.
 */
export declare function matrixStep(key: string, from: MatrixAt, lengths: readonly number[], ctrl: boolean): MatrixAt | null;