gerrit.onap Code Review - sdc/sdc-workflow-designer.git/blob

   1 /**
   2  * @license
   3  * Copyright Google Inc. All Rights Reserved.
   4  *
   5  * Use of this source code is governed by an MIT-style license that can be
   6  * found in the LICENSE file at https://angular.io/license
   7  */
   8 /* tslint:disable:array-type member-access variable-name typedef
   9  only-arrow-functions directive-class-suffix component-class-suffix
  10  component-selector*/
  11 import {ViewportRuler} from '../position/viewport-ruler';
  12
  13 import {ScrollStrategy} from './scroll-strategy';
  14
  15 /**
  16  * Strategy that will prevent the user from scrolling while the overlay is
  17  * visible.
  18  */
  19 export class BlockScrollStrategy implements ScrollStrategy {
  20   private _previousHTMLStyles = {top: '', left: ''};
  21   private _previousScrollPosition: {top: number, left: number};
  22   private _isEnabled = false;
  23
  24   constructor(private _viewportRuler: ViewportRuler) {}
  25
  26   attach() {
  27     //
  28   }
  29
  30   enable() {
  31         if (this._canBeEnabled()) {
  32                 const root = document.documentElement;
  33
  34                 this._previousScrollPosition =
  35                         this._viewportRuler.getViewportScrollPosition();
  36
  37       // Cache the previous inline styles in case the user had set them.
  38                 this._previousHTMLStyles.left = root.style.left || '';
  39                 this._previousHTMLStyles.top = root.style.top || '';
  40
  41       // Note: we're using the `html` node, instead of the `body`, because the
  42       // `body` may have the user agent margin, whereas the `html` is guaranteed
  43       // not to have one.
  44                 root.style.left = `${- this._previousScrollPosition.left}px`;
  45                 root.style.top = `${- this._previousScrollPosition.top}px`;
  46                 root.classList.add('cdk-global-scrollblock');
  47                 this._isEnabled = true;
  48         }
  49   }
  50
  51   disable() {
  52         if (this._isEnabled) {
  53                 this._isEnabled = false;
  54                 document.documentElement.style.left = this._previousHTMLStyles.left;
  55                 document.documentElement.style.top = this._previousHTMLStyles.top;
  56                 document.documentElement.classList.remove('cdk-global-scrollblock');
  57                 window.scroll(
  58                         this._previousScrollPosition.left, this._previousScrollPosition.top);
  59         }
  60   }
  61
  62   private _canBeEnabled(): boolean {
  63     // Since the scroll strategies can't be singletons, we have to use a global
  64     // CSS class
  65     // (`cdk-global-scrollblock`) to make sure that we don't try to disable
  66     // global scrolling multiple times.
  67         if (document.documentElement.classList.contains('cdk-global-scrollblock') ||
  68                 this._isEnabled) {
  69                 return false;
  70         }
  71
  72         const body = document.body;
  73         const viewport = this._viewportRuler.getViewportRect();
  74         return body.scrollHeight > viewport.height ||
  75                 body.scrollWidth > viewport.width;
  76   }
  77 }