angular-docs-cn/modules/@angular/platform-browser/src/dom/shared_styles_host.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {Inject, Injectable} from '@angular/core';

import {DOCUMENT} from './dom_tokens';

@Injectable()
export class SharedStylesHost {
  /** @internal */
  _styles: string[] = [];
  /** @internal */
  _stylesSet = new Set<string>();

  constructor() {}

  addStyles(styles: string[]) {
    const additions: any[] /** TODO #9100 */ = [];
    styles.forEach(style => {
      if (!this._stylesSet.has(style)) {
        this._stylesSet.add(style);
        this._styles.push(style);
        additions.push(style);
      }
    });
    this.onStylesAdded(additions);
  }

  onStylesAdded(additions: string[]) {}

  getAllStyles(): string[] { return this._styles; }
}

@Injectable()
export class DomSharedStylesHost extends SharedStylesHost {
  private _hostNodes = new Set<Node>();
  constructor(@Inject(DOCUMENT) doc: any) {
    super();
    this._hostNodes.add(doc.head);
  }
  /** @internal */
  _addStylesToHost(styles: string[], host: Node) {
    for (let i = 0; i < styles.length; i++) {
      const styleEl = document.createElement('style');
      styleEl.textContent = styles[i];
      host.appendChild(styleEl);
    }
  }
  addHost(hostNode: Node) {
    this._addStylesToHost(this._styles, hostNode);
    this._hostNodes.add(hostNode);
  }
  removeHost(hostNode: Node) { this._hostNodes.delete(hostNode); }

  onStylesAdded(additions: string[]) {
    this._hostNodes.forEach((hostNode) => { this._addStylesToHost(additions, hostNode); });
  }
}