import type { SpreadMode } from './spread.js';
import type { LoadProgress } from '../source/types.js';
export type Listener<T> = (payload: T) => void;
/** Events typed as `void` are emitted with no payload argument. */
type PayloadArgs<T> = [T] extends [void] ? [] : [payload: T];
/** Minimal typed event emitter keyed by an event map. */
export declare class Emitter<Events> {
    #private;
    /** Subscribe; returns an unsubscribe function. */
    on<K extends keyof Events>(type: K, listener: Listener<Events[K]>): () => void;
    off<K extends keyof Events>(type: K, listener: Listener<Events[K]>): void;
    emit<K extends keyof Events>(type: K, ...args: PayloadArgs<Events[K]>): void;
    clear(): void;
}
/**
 * Public event surface of a Zine instance. Payloads are provisional and will
 * firm up as the engine wires the emitters that fire them.
 */
export interface ZineEventMap {
    ready: void;
    flipStart: {
        from: number;
        to: number;
    };
    flipEnd: {
        page: number;
    };
    pageChanged: {
        page: number;
    };
    /** Pages regrouped: the spread mode changed, or a narrow container forced one page. */
    spreadChanged: {
        mode: SpreadMode;
        singlePage: boolean;
    };
    zoomChanged: {
        scale: number;
    };
    /** The document is downloading. Fires only for sources that report byte progress (a PDF from a
     *  URL); use it to drive a custom loading indicator, and hide it on `ready`. */
    progress: LoadProgress;
    sourceError: {
        index: number;
        error: unknown;
    };
    rendererFallback: {
        from: string;
        to: string;
    };
}
export type ZineEmitter = Emitter<ZineEventMap>;
export {};