Overleaf/services/web/frontend/js/ide/SafariScrollPatcher.js

/* eslint-disable
    max-len,
    no-return-assign,
    no-unused-vars,
*/
// TODO: This file was created by bulk-decaffeinate.
// Fix any style issues and re-enable lint.
/*
 * decaffeinate suggestions:
 * DS102: Remove unnecessary code created because of implicit returns
 * DS207: Consider shorter variations of null checks
 * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
 */
let SafariScrollPatcher

export default (SafariScrollPatcher = class SafariScrollPatcher {
  constructor($scope) {
    this.isOverAce = false // Flag to control if the pointer is over Ace.
    this.pdfDiv = null
    this.aceDiv = null

    // Start listening to PDF wheel events when the pointer leaves the PDF region.
    // P.S. This is the problem in a nutshell: although the pointer is elsewhere,
    // wheel events keep being dispatched to the PDF.
    this.handlePdfDivMouseLeave = () => {
      return this.pdfDiv.addEventListener('wheel', this.dispatchToAce)
    }

    // Stop listening to wheel events when the pointer enters the PDF region. If
    // the pointer is over the PDF, native behaviour is adequate.
    this.handlePdfDivMouseEnter = () => {
      return this.pdfDiv.removeEventListener('wheel', this.dispatchToAce)
    }

    // Set the "pointer over Ace" flag as false, when the mouse leaves its area.
    this.handleAceDivMouseLeave = () => {
      return (this.isOverAce = false)
    }

    // Set the "pointer over Ace" flag as true, when the mouse enters its area.
    this.handleAceDivMouseEnter = () => {
      return (this.isOverAce = true)
    }

    // Grab the elements (pdfDiv, aceDiv) and set the "hover" event listeners.
    // If elements are already defined, clear existing event listeners and do
    // the process again (grab elements, set listeners).
    this.setListeners = () => {
      this.isOverAce = false

      // If elements aren't null, remove existing listeners.
      if (this.pdfDiv != null) {
        this.pdfDiv.removeEventListener(this.handlePdfDivMouseLeave)
        this.pdfDiv.removeEventListener(this.handlePdfDivMouseEnter)
      }

      if (this.aceDiv != null) {
        this.aceDiv.removeEventListener(this.handleAceDivMouseLeave)
        this.aceDiv.removeEventListener(this.handleAceDivMouseEnter)
      }

      // Grab elements.
      this.pdfDiv = document.querySelector('.pdfjs-viewer') // Grab the PDF div.
      this.aceDiv = document.querySelector('.ace_content') // Also the editor.

      // Set hover-related listeners.
      this.pdfDiv.addEventListener('mouseleave', this.handlePdfDivMouseLeave)
      this.pdfDiv.addEventListener('mouseenter', this.handlePdfDivMouseEnter)
      this.aceDiv.addEventListener('mouseleave', this.handleAceDivMouseLeave)
      return this.aceDiv.addEventListener(
        'mouseenter',
        this.handleAceDivMouseEnter
      )
    }

    // Handler for wheel events on the PDF.
    // If the pointer is over Ace, grab the event, prevent default behaviour
    // and dispatch it to Ace.
    this.dispatchToAce = e => {
      if (this.isOverAce) {
        // If this is logged, the problem just happened: the event arrived
        // here (the PDF wheel handler), but it should've gone to Ace.

        // Small timeout - if we dispatch immediately, an exception is thrown.
        window.setTimeout(() => {
          // Dispatch the exact same event to Ace (this will keep values
          // values e.g. `wheelDelta` consistent with user interaction).
          return this.aceDiv.dispatchEvent(e)
        }, 1)

        // Avoid scrolling the PDF, as we assume this was intended to the
        // editor.
        return e.preventDefault()
      }
    }

    // "loaded" event is emitted from the pdfViewer controller $scope. This means
    // that the previous PDF DOM element was destroyed and a new one is available,
    // so we need to grab the elements and set the listeners again.
    $scope.$on('loaded', () => {
      return this.setListeners()
    })
  }
})