import {createRectInit, getContentRect} from './utils/geometry.js';
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/**
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* Class that is responsible for computations of the content rectangle of
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* provided DOM element and for keeping track of it's changes.
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*/
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export default class ResizeObservation {
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/**
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* Reference to the observed element.
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*
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* @type {Element}
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*/
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target;
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/**
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* Broadcasted width of content rectangle.
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*
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* @type {number}
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*/
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broadcastWidth = 0;
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/**
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* Broadcasted height of content rectangle.
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*
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* @type {number}
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*/
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broadcastHeight = 0;
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/**
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* Reference to the last observed content rectangle.
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*
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* @private {DOMRectInit}
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*/
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contentRect_ = createRectInit(0, 0, 0, 0);
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/**
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* Creates an instance of ResizeObservation.
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*
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* @param {Element} target - Element to be observed.
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*/
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constructor(target) {
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this.target = target;
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}
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/**
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* Updates content rectangle and tells whether it's width or height properties
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* have changed since the last broadcast.
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*
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* @returns {boolean}
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*/
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isActive() {
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const rect = getContentRect(this.target);
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this.contentRect_ = rect;
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return (
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rect.width !== this.broadcastWidth ||
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rect.height !== this.broadcastHeight
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);
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}
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/**
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* Updates 'broadcastWidth' and 'broadcastHeight' properties with a data
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* from the corresponding properties of the last observed content rectangle.
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*
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* @returns {DOMRectInit} Last observed content rectangle.
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*/
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broadcastRect() {
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const rect = this.contentRect_;
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this.broadcastWidth = rect.width;
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this.broadcastHeight = rect.height;
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return rect;
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}
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}
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