import { AfterContentInit, ChangeDetectorRef, DoCheck, ElementRef, DefaultIterableDiffer, IterableDiffers, NgZone, OnDestroy, Renderer, TrackByFn } from '@angular/core';
import { Config } from '../../config/config';
import { Content, ScrollEvent } from '../content/content';
import { DomController } from '../../platform/dom-controller';
import { Platform } from '../../platform/platform';
import { ViewController } from '../../navigation/view-controller';
import { VirtualCell, VirtualData, VirtualNode } from './virtual-util';
import { VirtualItem } from './virtual-item';
import { VirtualFooter } from './virtual-footer';
import { VirtualHeader } from './virtual-header';
/**
 * @name VirtualScroll
 * @description
 * Virtual Scroll displays a virtual, "infinite" list. An array of records
 * is passed to the virtual scroll containing the data to create templates
 * for. The template created for each record, referred to as a cell, can
 * consist of items, headers, and footers.
 *
 * For performance reasons, not every record in the list is rendered at once;
 * instead a small subset of records (enough to fill the viewport) are rendered
 * and reused as the user scrolls.
 *
 * ### The Basics
 *
 * The array of records should be passed to the `virtualScroll` property.
 * The data given to the `virtualScroll` property must be an array. An item
 * template with the `*virtualItem` property is required in the `virtualScroll`.
 * The `virtualScroll` and `*virtualItem` properties can be added to any element.
 *
 * ```html
 * <ion-list [virtualScroll]="items">
 *
 *   <ion-item *virtualItem="let item">
 *     {% raw %}{{ item }}{% endraw %}
 *   </ion-item>
 *
 * </ion-list>
 * ```
 *
 *
 * ### Section Headers and Footers
 *
 * Section headers and footers are optional. They can be dynamically created
 * from developer-defined functions. For example, a large list of contacts
 * usually has a divider for each letter in the alphabet. Developers provide
 * their own custom function to be called on each record. The logic in the
 * custom function should determine whether to create the section template
 * and what data to provide to the template. The custom function should
 * return `null` if a template shouldn't be created.
 *
 * ```html
 * <ion-list [virtualScroll]="items" [headerFn]="myHeaderFn">
 *
 *   <ion-item-divider *virtualHeader="let header">
 *     Header: {% raw %}{{ header }}{% endraw %}
 *   </ion-item-divider>
 *
 *   <ion-item *virtualItem="let item">
 *     Item: {% raw %}{{ item }}{% endraw %}
 *   </ion-item>
 *
 * </ion-list>
 * ```
 *
 * Below is an example of a custom function called on every record. It
 * gets passed the individual record, the record's index number,
 * and the entire array of records. In this example, after every 20
 * records a header will be inserted. So between the 19th and 20th records,
 * between the 39th and 40th, and so on, a `<ion-item-divider>` will
 * be created and the template's data will come from the function's
 * returned data.
 *
 * ```ts
 * myHeaderFn(record, recordIndex, records) {
 *   if (recordIndex % 20 === 0) {
 *     return 'Header ' + recordIndex;
 *   }
 *   return null;
 * }
 * ```
 *
 *
 * ### Approximate Widths and Heights
 *
 * If the height of items in the virtual scroll are not close to the
 * default size of 40px, it is extremely important to provide an value for
 * approxItemHeight height. An exact pixel-perfect size is not necessary,
 * but without an estimate the virtual scroll will not render correctly.
 *
 * The approximate width and height of each template is used to help
 * determine how many cells should be created, and to help calculate
 * the height of the scrollable area. Note that the actual rendered size
 * of each cell comes from the app's CSS, whereas this approximation
 * is only used to help calculate initial dimensions.
 *
 * It's also important to know that Ionic's default item sizes have
 * slightly different heights between platforms, which is perfectly fine.
 *
 *
 * ### Images Within Virtual Scroll
 *
 * HTTP requests, image decoding, and image rendering can cause jank while
 * scrolling. In order to better control images, Ionic provides `<ion-img>`
 * to manage HTTP requests and image rendering. While scrolling through items
 * quickly, `<ion-img>` knows when and when not to make requests, when and
 * when not to render images, and only loads the images that are viewable
 * after scrolling. [Read more about `ion-img`.](../../img/Img/)
 *
 * It's also important for app developers to ensure image sizes are locked in,
 * and after images have fully loaded they do not change size and affect any
 * other element sizes. Simply put, to ensure rendering bugs are not introduced,
 * it's vital that elements within a virtual item does not dynamically change.
 *
 * For virtual scrolling, the natural effects of the `<img>` are not desirable
 * features. We recommend using the `<ion-img>` component over the native
 * `<img>` element because when an `<img>` element is added to the DOM, it
 * immediately makes a HTTP request for the image file. Additionally, `<img>`
 * renders whenever it wants which could be while the user is scrolling. However,
 * `<ion-img>` is governed by the containing `ion-content` and does not render
 * images while scrolling quickly.
 *
 * ```html
 * <ion-list [virtualScroll]="items">
 *
 *   <ion-item *virtualItem="let item">
 *     <ion-avatar item-left>
 *       <ion-img [src]="item.avatarUrl"></ion-img>
 *     </ion-avatar>
 *    {% raw %} {{ item.firstName }} {{ item.lastName }}{% endraw %}
 *   </ion-item>
 *
 * </ion-list>
 * ```
 *
 *
 * ### Custom Components
 *
 * If a custom component is going to be used within Virtual Scroll, it's best
 * to wrap it with a good old `<div>` to ensure the component is rendered
 * correctly. Since each custom component's implementation and internals can be
 * quite different, wrapping within a `<div>` is a safe way to make sure
 * dimensions are measured correctly.
 *
 * ```html
 * <ion-list [virtualScroll]="items">
 *
 *   <div *virtualItem="let item">
 *     <my-custom-item [item]="item">
 *       {% raw %} {{ item }}{% endraw %}
 *     </my-custom-item>
 *   </div>
 *
 * </ion-list>
 * ```
 *
 *
 * ## Virtual Scroll Performance Tips
 *
 * #### iOS Cordova WKWebView
 *
 * When deploying to iOS with Cordova, it's highly recommended to use the
 * [WKWebView plugin](http://blog.ionic.io/cordova-ios-performance-improvements-drop-in-speed-with-wkwebview/)
 * in order to take advantage of iOS's higher performimg webview. Additionally,
 * WKWebView is superior at scrolling efficiently in comparision to the older
 * UIWebView.
 *
 * #### Lock in element dimensions and locations
 *
 * In order for virtual scroll to efficiently size and locate every item, it's
 * very important every element within each virtual item does not dynamically
 * change its dimensions or location. The best way to ensure size and location
 * does not change, it's recommended each virtual item has locked in its size
 * via CSS.
 *
 * #### Use `ion-img` for images
 *
 * When including images within Virtual Scroll, be sure to use
 * [`ion-img`](../img/Img/) rather than the standard `<img>` HTML element.
 * With `ion-img`, images are lazy loaded so only the viewable ones are
 * rendered, and HTTP requests are efficiently controlled while scrolling.
 *
 * #### Set Approximate Widths and Heights
 *
 * As mentioned above, all elements should lock in their dimensions. However,
 * virtual scroll isn't aware of the dimensions until after they have been
 * rendered. For the initial render, virtual scroll still needs to set
 * how many items should be built. With "approx" property inputs, such as
 * `approxItemHeight`, we're able to give virtual sroll an approximate size,
 * therefore allowing virtual scroll to decide how many items should be
 * created.
 *
 * #### Changing dataset should use `virtualTrackBy`
 *
 * It is possible for the identities of elements in the iterator to change
 * while the data does not. This can happen, for example, if the iterator
 * produced from an RPC to the server, and that RPC is re-run. Even if the
 * "data" hasn't changed, the second response will produce objects with
 * different identities, and Ionic will tear down the entire DOM and rebuild
 * it. This is an expensive operation and should be avoided if possible.
 *
 * #### Efficient headers and footer functions
 *
 * Each virtual item must stay extremely efficient, but one way to really
 * kill its performance is to perform any DOM operations within section header
 * and footer functions. These functions are called for every record in the
 * dataset, so please make sure they're performant.
 *
 */
export declare class VirtualScroll implements DoCheck, AfterContentInit, OnDestroy {
    private _iterableDiffers;
    private _elementRef;
    private _renderer;
    private _zone;
    private _cd;
    private _content;
    private _plt;
    private _ctrl;
    private _config;
    private _dom;
    _differ: DefaultIterableDiffer<any>;
    _scrollSub: any;
    _scrollEndSub: any;
    _resizeSub: any;
    _init: boolean;
    _lastEle: boolean;
    _hdrFn: Function;
    _ftrFn: Function;
    _records: any[];
    _cells: VirtualCell[];
    _nodes: VirtualNode[];
    _vHeight: number;
    _lastCheck: number;
    _data: VirtualData;
    _queue: number;
    _recordSize: number;
    _itmTmp: VirtualItem;
    _hdrTmp: VirtualHeader;
    _ftrTmp: VirtualFooter;
    /**
     * @input {array} The data that builds the templates within the virtual scroll.
     * This is the same data that you'd pass to `*ngFor`. It's important to note
     * that when this data has changed, then the entire virtual scroll is reset,
     * which is an expensive operation and should be avoided if possible.
     */
    virtualScroll: any;
    /**
     * @input {number} The buffer ratio is used to decide how many cells
     * should get created when initially rendered. The number is a
     * multiplier against the viewable area's height. For example, if it
     * takes `20` cells to fill up the height of the viewable area, then
     * with a buffer ratio of `3` it will create `60` cells that are
     * available for reuse while scrolling. For better performance, it's
     * better to have more cells than what are required to fill the
     * viewable area. Default is `3`.
     */
    bufferRatio: number;
    /**
     * @input {string} The approximate width of each item template's cell.
     * This dimension is used to help determine how many cells should
     * be created when initialized, and to help calculate the height of
     * the scrollable area. This value can use either `px` or `%` units.
     * Note that the actual rendered size of each cell comes from the
     * app's CSS, whereas this approximation is used to help calculate
     * initial dimensions before the item has been rendered. Default is
     * `100%`.
     */
    approxItemWidth: string;
    /**
     * @input {string} It is important to provide this
     * if virtual item height will be significantly larger than the default
     * The approximate height of each virtual item template's cell.
     * This dimension is used to help determine how many cells should
     * be created when initialized, and to help calculate the height of
     * the scrollable area. This height value can only use `px` units.
     * Note that the actual rendered size of each cell comes from the
     * app's CSS, whereas this approximation is used to help calculate
     * initial dimensions before the item has been rendered. Default is
     * `40px`.
     */
    approxItemHeight: string;
    /**
     * @input {string} The approximate width of each header template's cell.
     * This dimension is used to help determine how many cells should
     * be created when initialized, and to help calculate the height of
     * the scrollable area. This value can use either `px` or `%` units.
     * Note that the actual rendered size of each cell comes from the
     * app's CSS, whereas this approximation is used to help calculate
     * initial dimensions. Default is `100%`.
     */
    approxHeaderWidth: string;
    /**
     * @input {string} The approximate height of each header template's cell.
     * This dimension is used to help determine how many cells should
     * be created when initialized, and to help calculate the height of
     * the scrollable area. This height value can only use `px` units.
     * Note that the actual rendered size of each cell comes from the
     * app's CSS, whereas this approximation is used to help calculate
     * initial dimensions before the item has been rendered. Default is `40px`.
     */
    approxHeaderHeight: string;
    /**
     * @input {string} The approximate width of each footer template's cell.
     * This dimension is used to help determine how many cells should
     * be created when initialized, and to help calculate the height of
     * the scrollable area. This value can use either `px` or `%` units.
     * Note that the actual rendered size of each cell comes from the
     * app's CSS, whereas this approximation is used to help calculate
     * initial dimensions before the item has been rendered. Default is `100%`.
     */
    approxFooterWidth: string;
    /**
     * @input {string} The approximate height of each footer template's cell.
     * This dimension is used to help determine how many cells should
     * be created when initialized, and to help calculate the height of
     * the scrollable area. This height value can only use `px` units.
     * Note that the actual rendered size of each cell comes from the
     * app's CSS, whereas this approximation is used to help calculate
     * initial dimensions before the item has been rendered. Default is `40px`.
     */
    approxFooterHeight: string;
    /**
     * @input {function} Section headers and the data used within its given
     * template can be dynamically created by passing a function to `headerFn`.
     * For example, a large list of contacts usually has dividers between each
     * letter in the alphabet. App's can provide their own custom `headerFn`
     * which is called with each record within the dataset. The logic within
     * the header function can decide if the header template should be used,
     * and what data to give to the header template. The function must return
     * `null` if a header cell shouldn't be created.
     */
    headerFn: Function;
    /**
     * @input {function} Section footers and the data used within its given
     * template can be dynamically created by passing a function to `footerFn`.
     * The logic within the footer function can decide if the footer template
     * should be used, and what data to give to the footer template. The function
     * must return `null` if a footer cell shouldn't be created.
     */
    footerFn: Function;
    /**
     * @input {function} Same as `ngForTrackBy` which can be used on `ngFor`.
     */
    virtualTrackBy: TrackByFn;
    constructor(_iterableDiffers: IterableDiffers, _elementRef: ElementRef, _renderer: Renderer, _zone: NgZone, _cd: ChangeDetectorRef, _content: Content, _plt: Platform, _ctrl: ViewController, _config: Config, _dom: DomController);
    /**
     * @hidden
     */
    ngDoCheck(): void;
    readUpdate(needClean: boolean): void;
    writeUpdate(needClean: boolean): void;
    private calcDimensions();
    private _changes();
    /**
     * @hidden
     * DOM WRITE
     */
    renderVirtual(needClean: boolean): void;
    /**
     * @private
     */
    resize(): void;
    /**
     * @hidden
     */
    private _stepDOMWrite();
    /**
     * @private
     */
    private _stepChangeDetection();
    /**
     * @private
     */
    private _stepNoChanges();
    /**
     * @private
     */
    scrollUpdate(ev: ScrollEvent): void;
    /**
     * @hidden
     * DOM WRITE
     */
    scrollEnd(ev: ScrollEvent): void;
    /**
     * NO DOM
     */
    private _listeners();
    /**
     * DOM WRITE
     */
    private _setHeight(newVirtualHeight);
    /**
     * @hidden
     */
    ngAfterContentInit(): void;
    setElementClass(className: string, add: boolean): void;
    /**
     * @hidden
     */
    ngOnDestroy(): void;
}
