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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,100 +1,22 @@ | ||
| import { NgZone } from '@angular/core'; | ||
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| /** | ||
| * Observes changes to an elements visibility. | ||
| * https://medium.com/@amcdnl/javascript-s-new-intersectionobserver-cdce8a73bef8#.evn5twug3 | ||
| * | ||
| * Example: | ||
| * | ||
| * var elm = document.getElementById("panda"); | ||
| * new VisibilityObserver(elm, function() { | ||
| * alert('PAndas rock!'); | ||
| * }); | ||
| * | ||
| */ | ||
| export class VisibilityObserver { | ||
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| observer: IntersectionObserver; | ||
| callback: any; | ||
| timeout: any; | ||
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| constructor(element: any, callback: any, zone: NgZone) { | ||
| this.callback = callback; | ||
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| /* | ||
| // this is not working... | ||
| if(window.IntersectionObserver) { | ||
| this.observer = new IntersectionObserver( | ||
| this.processChanges.bind(this), { threshold: [0.5] }); | ||
| this.observer.observe(element); | ||
| } else { this.runPolyfill(element); } | ||
| */ | ||
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| this.runPolyfill(element, zone); | ||
| } | ||
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| runPolyfill(element: any, zone: NgZone) { | ||
| let checkVisibility = () => { | ||
| const { width, height } = element.getBoundingClientRect(); | ||
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| if (width && height) { | ||
| clearTimeout(this.timeout); | ||
| if(this.callback) { | ||
| zone.run(this.callback.bind(this)); | ||
| } | ||
| } else { | ||
| clearTimeout(this.timeout); | ||
| zone.runOutsideAngular(() => { | ||
| this.timeout = setTimeout(() => checkVisibility(), 50); | ||
| }); | ||
| } | ||
| }; | ||
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| checkVisibility(); | ||
| } | ||
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| isVisible(boundingClientRect, intersectionRect) { | ||
| return ((intersectionRect.width * intersectionRect.height) / | ||
| (boundingClientRect.width * boundingClientRect.height) >= 0.5); | ||
| } | ||
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| visibleTimerCallback(element, observer) { | ||
| delete element.visibleTimeout; | ||
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| // Process any pending observations | ||
| this.processChanges(observer.takeRecords()); | ||
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| if ('isVisible' in element) { | ||
| delete element.isVisible; | ||
| if(this.callback) this.callback(); | ||
| observer.unobserve(element); | ||
| export function checkVisibility(element: any, callback: any, zone: NgZone) { | ||
| let timeout; | ||
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| function check() { | ||
| // https://davidwalsh.name/offsetheight-visibility | ||
| const { offsetHeight, offsetWidth } = element; | ||
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| if (offsetHeight && offsetWidth) { | ||
| clearTimeout(timeout); | ||
| if(callback) zone.run(() => callback()); | ||
| } else { | ||
| clearTimeout(timeout); | ||
| zone.runOutsideAngular(() => { | ||
| timeout = setTimeout(() => check(), 50); | ||
| }); | ||
| } | ||
| } | ||
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| processChanges(changes) { | ||
| changes.forEach((changeRecord) => { | ||
| let element = changeRecord.target; | ||
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| element.isVisible = this.isVisible( | ||
| changeRecord.boundingClientRect, | ||
| changeRecord.intersectionRect); | ||
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| if ('isVisible' in element) { | ||
| // Transitioned from hidden to visible | ||
| element.visibleTimeout = setTimeout( | ||
| this.visibleTimerCallback.bind(this), | ||
| 1000, | ||
| element, | ||
| this.observer); | ||
| } else { | ||
| // Transitioned from visible to hidden | ||
| if ('visibleTimeout' in element) { | ||
| clearTimeout(element.visibleTimeout); | ||
| delete element.visibleTimeout; | ||
| } | ||
| } | ||
| }); | ||
| } | ||
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| check(); | ||
| } |