/**
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/LICENSE
 */
import { Direction, Directionality } from '@angular/cdk/bidi';
import { Platform } from '@angular/cdk/platform';
import { ChangeDetectorRef, ElementRef, EventEmitter, NgZone, OnChanges, OnDestroy, OnInit, SimpleChanges, TemplateRef } from '@angular/core';
import { NzConfigKey, NzConfigService } from 'ng-zorro-antd/core/config';
import { NzDestroyService, NzScrollService } from 'ng-zorro-antd/core/services';
import { NumberInput, NzSafeAny } from 'ng-zorro-antd/core/types';
import * as i0 from "@angular/core";
export declare class NzBackTopComponent implements OnInit, OnDestroy, OnChanges {
    private doc;
    nzConfigService: NzConfigService;
    private scrollSrv;
    private platform;
    private cd;
    private zone;
    private cdr;
    private destroy$;
    private directionality;
    readonly _nzModuleName: NzConfigKey;
    static ngAcceptInputType_nzVisibilityHeight: NumberInput;
    static ngAcceptInputType_nzDuration: NumberInput;
    private scrollListenerDestroy$;
    private target;
    visible: boolean;
    dir: Direction;
    nzTemplate?: TemplateRef<void>;
    nzVisibilityHeight: number;
    nzTarget?: string | HTMLElement;
    nzDuration: number;
    readonly nzClick: EventEmitter<boolean>;
    set backTop(backTop: ElementRef<HTMLElement> | undefined);
    private backTopClickSubscription;
    constructor(doc: NzSafeAny, nzConfigService: NzConfigService, scrollSrv: NzScrollService, platform: Platform, cd: ChangeDetectorRef, zone: NgZone, cdr: ChangeDetectorRef, destroy$: NzDestroyService, directionality: Directionality);
    ngOnInit(): void;
    private getTarget;
    private handleScroll;
    private registerScrollEvent;
    ngOnDestroy(): void;
    ngOnChanges(changes: SimpleChanges): void;
    static ɵfac: i0.ɵɵFactoryDeclaration<NzBackTopComponent, [null, null, null, null, null, null, null, null, { optional: true; }]>;
    static ɵcmp: i0.ɵɵComponentDeclaration<NzBackTopComponent, "nz-back-top", ["nzBackTop"], { "nzTemplate": "nzTemplate"; "nzVisibilityHeight": "nzVisibilityHeight"; "nzTarget": "nzTarget"; "nzDuration": "nzDuration"; }, { "nzClick": "nzClick"; }, never, never, false>;
}