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// Directives
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import { Scroll } from '../../directives'
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// Utilities
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import { consoleWarn } from '../../util/console'
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// Types
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import Vue from 'vue'
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/**
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* Scrollable
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*
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* Used for monitoring scrolling and
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* invoking functions based upon
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* scrolling thresholds being
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* met.
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*/
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/* @vue/component */
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export default Vue.extend({
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name: 'scrollable',
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directives: { Scroll },
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props: {
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scrollTarget: String,
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scrollThreshold: [String, Number],
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},
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data: () => ({
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currentScroll: 0,
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currentThreshold: 0,
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isActive: false,
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isScrollingUp: false,
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previousScroll: 0,
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savedScroll: 0,
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target: null as Element | null,
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}),
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computed: {
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/**
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* A computed property that returns
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* whether scrolling features are
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* enabled or disabled
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*/
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canScroll (): boolean {
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return typeof window !== 'undefined'
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},
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/**
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* The threshold that must be met before
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* thresholdMet function is invoked
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*/
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computedScrollThreshold (): number {
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return this.scrollThreshold
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? Number(this.scrollThreshold)
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: 300
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},
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},
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watch: {
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isScrollingUp () {
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this.savedScroll = this.savedScroll || this.currentScroll
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},
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isActive () {
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this.savedScroll = 0
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},
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},
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mounted () {
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if (this.scrollTarget) {
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this.target = document.querySelector(this.scrollTarget)
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if (!this.target) {
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consoleWarn(`Unable to locate element with identifier ${this.scrollTarget}`, this)
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}
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}
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},
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methods: {
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onScroll () {
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if (!this.canScroll) return
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this.previousScroll = this.currentScroll
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this.currentScroll = this.target
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? this.target.scrollTop
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: window.pageYOffset
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this.isScrollingUp = this.currentScroll < this.previousScroll
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this.currentThreshold = Math.abs(this.currentScroll - this.computedScrollThreshold)
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this.$nextTick(() => {
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if (
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Math.abs(this.currentScroll - this.savedScroll) >
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this.computedScrollThreshold
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) this.thresholdMet()
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})
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},
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/**
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* The method invoked when
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* scrolling in any direction
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* has exceeded the threshold
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*/
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thresholdMet () { /* noop */ },
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},
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})
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mcdmaster