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