_windowResize() {
    clearTimeout(this.w.globals.resizeTimer)
    this.w.globals.resizeTimer = window.setTimeout(() => {
      this.w.globals.resized = true
      this.w.globals.dataChanged = false

      // we need to redraw the whole chart on window resize (with a small delay).
      this.ctx.update()
    }, 150)
  }
Handle window resize and re-draw the whole chart.