/**
 * The accessible feedback channel of the capture visualizer: a visible instruction plate
 * (aria-hidden) plus visually hidden live regions for the screen reader.
 *
 * A message must stay unchanged for settleMs before it counts. The plate then shows it right away,
 * while the spoken channel changes no faster than the screen reader can speak the previous
 * message; intermediate messages are dropped rather than queued.
 */
export declare class FeedbackAnnouncer {
    private static readonly settleMs;
    private static readonly minIntervalMs;
    private static readonly maxIntervalMs;
    private static readonly msPerWord;
    private static readonly owners;
    private container;
    private visibleTextEl;
    private politeRegion;
    private alertRegion;
    private pending;
    private settled;
    private spoken;
    private settleTimer;
    private voiceTimer;
    private spokenStep;
    private spokenText;
    private plateVisible;
    private lastSpokenAt;
    constructor(containerElement: HTMLElement);
    /** Call on every processed frame. immediate skips the settle window and the pacing gate,
     *  assertive marks the outcome of the flow, which also interrupts the screen reader. */
    setMessage(instruction: string, step: string, immediate?: boolean, assertive?: boolean): void;
    /** Hiding the plate does not silence the spoken channel: not drawing text over the camera view
     *  must not take the guidance away from a screen reader. */
    setPlateVisible(visible: boolean): void;
    /** Stop the timers and clear the visible plate. The DOM nodes stay in the container: a live
     *  region has to exist before it is written, so re-inserting it at the start of every capture
     *  would cost the first announcement (iOS VoiceOver in particular). */
    reset(): void;
    private forgetSpoken;
    private isOwner;
    private stopTimer;
    private createOrReuseNodes;
    /** Visually hidden by a 1px clipped box, NOT display:none - that would drop the region from
     *  the accessibility tree. */
    private createLiveRegion;
    private writePlate;
    private writeLive;
    /** Time a screen reader needs to speak the text, used as the gap before the next message. */
    private static speakTimeMs;
    /** Speak the settled message once the pacing gate opens; silence and immediate messages skip
     *  it. Whatever is settled when the gate opens wins, so intermediate messages are dropped. */
    private scheduleVoice;
    private speak;
}
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