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import * as debug from 'debug'
import {
AfterViewInit,
ChangeDetectorRef,
ContentChild,
Directive,
ElementRef,
EmbeddedViewRef,
EventEmitter,
OnDestroy,
Output,
TemplateRef,
ViewContainerRef
} from '@angular/core'
const debugLogger = debug('peertube:main:DeferLoadingDirective')
@Directive({
selector: '[myDeferLoading]'
})
export class DeferLoadingDirective implements AfterViewInit, OnDestroy {
@ContentChild(TemplateRef) template: TemplateRef<any>
@Output() loaded = new EventEmitter()
view: EmbeddedViewRef<any>
private observer: IntersectionObserver
constructor (
private el: ElementRef,
private viewContainer: ViewContainerRef,
private cd: ChangeDetectorRef
) { }
ngAfterViewInit () {
if (this.hasIncompatibleBrowser()) {
return this.load()
}
this.observer = new IntersectionObserver(entries => {
const entry = entries[0]
if (!entry.isIntersecting || entry.target !== this.el.nativeElement) return
this.observer.unobserve(this.el.nativeElement)
this.load()
}, { threshold: 0.1 })
this.observer.observe(this.el.nativeElement)
}
load () {
if (this.isLoaded()) return
debugLogger('Loading component')
this.viewContainer.clear()
this.view = this.viewContainer.createEmbeddedView(this.template, {}, 0)
this.loaded.emit()
this.cd.detectChanges()
}
isLoaded () {
return this.view != null
}
ngOnDestroy () {
this.view = null
if (this.observer) this.observer.disconnect()
}
private hasIncompatibleBrowser () {
return !('IntersectionObserver' in window)
}
}
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