How to use the gui.Scroll function in gui

render(ele, container => {
        const scroll = container.childAt(0)
        expect(scroll instanceof gui.Scroll).toBeTruthy()
        const size = scroll.getContentSize()
        // NOTE: The value may be not accurate in windows
        if (!win32) {
          expect(size.width).toBe(contentSize.width)
          expect(size.height).toBe(contentSize.height)
        }
        // expect(scroll.isOverlayScrollbar()).toBe(overlayScrollbar)
        const policies = scroll.getScrollbarPolicy()
        expect(policies[0]).toBe(hpolicy)
        // TODO: not work for vpolicy
        // expect(policies[1]).toBe(vpolicy)
        done()
      })
    })

constructor(mainWindow) {
    this.mainWindow = mainWindow
    this.account = null
    this.channelItems = []
    this.dmItems = []
    this.selectedChannelItem = null

    this.view = gui.Container.create()
    this.view.setStyle({width: 220})
    this.view.setBackgroundColor('#2F3241')

    this.accountHeader = new AccountHeader()
    this.view.addChildView(this.accountHeader.view)

    this.channelsListScroll = gui.Scroll.create()
    this.channelsListScroll.setStyle({flex: 1})
    if (process.platform === 'win32') {
      // On Windows there is no overlay scrollbar.
      this.channelsListScroll.setScrollbarPolicy('never', 'never')
    } else {
      // Force using overlay scrollbar.
      this.channelsListScroll.setOverlayScrollbar(true)
      this.channelsListScroll.setScrollbarPolicy('never', 'automatic')
    }
    this.view.addChildView(this.channelsListScroll)

    this.channelsList = gui.Container.create()
    this.channelsList.setStyle({paddingBottom: 15})
    this.channelsListScroll.setContentView(this.channelsList)

    this.channelTitle = new ChannelTitle('Channels')

constructor(mainWindow) {
    this.mainWindow = mainWindow
    this.channels = []

    this.view = gui.Container.create()
    this.view.setMouseDownCanMoveWindow(false)
    this.view.setBackgroundColor('#FFF')
    this.view.setStyle({flex: 1, padding: 20})

    this.entry = gui.Entry.create()
    this.entry.setStyle({width: '100%', marginBottom: 20})
    this.entry.onTextChange = this.onTextChange.bind(this)
    this.view.addChildView(this.entry)

    this.scroll = gui.Scroll.create()
    this.scroll.setStyle({flex: 1})
    this.scroll.setScrollbarPolicy('never', 'automatic')
    this.contentView = gui.Container.create()
    this.contentView.onDraw = this.draw.bind(this)
    this.scroll.setContentView(this.contentView)
    this.view.addChildView(this.scroll)

    this.hoverItem = null
    this.contentView.onMouseMove = this.onMouse.bind(this)
    this.contentView.onMouseEnter = this.onMouse.bind(this)
    this.contentView.onMouseLeave = this.onMouse.bind(this)
    this.contentView.onMouseUp = this.onClick.bind(this)
  }