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99 lines
3.1 KiB
Plaintext
99 lines
3.1 KiB
Plaintext
/*
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* Copyright 2020 Adobe. All rights reserved.
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* This file is licensed to you under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License. You may obtain a copy
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* of the License at http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under
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* the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
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* OF ANY KIND, either express or implied. See the License for the specific language
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* governing permissions and limitations under the License.
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*/
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import {Key} from '@react-types/shared';
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import {LayoutInfo} from './LayoutInfo';
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import {Virtualizer} from './Virtualizer';
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let KEY = 0;
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/**
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* `Virtualizer` creates instances of the `ReusableView` class to
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* represent views currently being displayed.
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*/
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export class ReusableView<T extends object, V> {
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/** The Virtualizer this view is a part of. */
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virtualizer: Virtualizer<T, V>;
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/** The LayoutInfo this view is currently representing. */
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layoutInfo: LayoutInfo | null;
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/** The content currently being displayed by this view, set by the virtualizer. */
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content: T | null;
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rendered: V | null;
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viewType: string;
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key: Key;
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children: Set<ChildView<T, V>>;
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reusableViews: Map<string, ChildView<T, V>[]>;
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constructor(virtualizer: Virtualizer<T, V>, viewType: string) {
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this.virtualizer = virtualizer;
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this.key = ++KEY;
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this.viewType = viewType;
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this.children = new Set();
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this.reusableViews = new Map();
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this.layoutInfo = null;
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this.content = null;
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this.rendered = null;
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}
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/**
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* Prepares the view for reuse. Called just before the view is removed from the DOM.
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*/
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prepareForReuse(): void {
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this.content = null;
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this.rendered = null;
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this.layoutInfo = null;
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}
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getReusableView(reuseType: string): ChildView<T, V> {
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// Reusable view queue should be FIFO so that DOM order remains consistent during scrolling.
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// For example, cells within a row should remain in the same order even if the row changes contents.
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// The cells within a row are removed from their parent in order. If the row is reused, the cells
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// should be reused in the new row in the same order they were before.
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let reusable = this.reusableViews.get(reuseType);
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let view = reusable && reusable.length > 0
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? reusable.shift()!
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: new ChildView<T, V>(this.virtualizer, this, reuseType);
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return view;
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}
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reuseChild(child: ChildView<T, V>): void {
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child.prepareForReuse();
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let reusable = this.reusableViews.get(child.viewType);
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if (!reusable) {
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reusable = [];
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this.reusableViews.set(child.viewType, reusable);
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}
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reusable.push(child);
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}
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}
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export class RootView<T extends object, V> extends ReusableView<T, V> {
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constructor(virtualizer: Virtualizer<T, V>) {
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super(virtualizer, 'root');
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}
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}
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export class ChildView<T extends object, V> extends ReusableView<T, V> {
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parent: ReusableView<T, V>;
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constructor(virtualizer: Virtualizer<T, V>, parent: ReusableView<T, V>, viewType: string) {
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super(virtualizer, viewType);
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this.parent = parent;
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}
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}
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