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// (C) Copyright 2015 Moodle Pty Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
import { Directive, ElementRef, EventEmitter, OnDestroy, OnInit, Output } from '@angular/core';
import { CoreDomUtils } from '@services/utils/dom';
/**
* Directive to listen when an element becomes visible.
*/
@Directive({
selector: '[onAppear]',
})
export class CoreOnAppearDirective implements OnInit, OnDestroy {
@Output() onAppear = new EventEmitter();
private element: HTMLElement;
private interval?: number;
constructor(element: ElementRef) {
this.element = element.nativeElement;
}
/**
* @inheritdoc
*/
ngOnInit(): void {
this.interval = window.setInterval(() => {
if (!CoreDomUtils.isElementVisible(this.element)) {
return;
}
this.onAppear.emit();
window.clearInterval(this.interval);
delete this.interval;
}, 50);
}
/**
* @inheritdoc
*/
ngOnDestroy(): void {
this.interval && window.clearInterval(this.interval);
}
}