focus overlay

bringFocusInsideOverlay() {
    return requestAnimationFrame(() => {
      // Container ref may be undefined between component mounting and Portal rendering
      // activeElement may be undefined in some rare cases in IE
      if (
        this.$refs.container == null ||
        document.activeElement == null ||
        !this.isShown
      ) {
        return
      }

      const isFocusOutsideModal = !this.$refs.container.contains(
        document.activeElement
      )
      if (isFocusOutsideModal) {
        // Element marked autofocus has higher priority than the other clowns
        const autofocusElement = <HTMLElement>this.$refs.container.querySelector(
          '[autofocus]'
        )
        const wrapperElement = <HTMLElement>this.$refs.container.querySelector('[tabindex]')
        const buttonElement = <HTMLElement>this.$refs.container.querySelector('button')

        if (autofocusElement) {
          autofocusElement.focus()
        } else if (wrapperElement) {
          wrapperElement.focus()
        } else if (buttonElement) {
          buttonElement.focus()
        }
      }
    })
  }

  bringFocusBackToTarget() {
    return requestAnimationFrame(() => {
      if (
        this.$refs.container == null ||
        document.activeElement == null
      ) {
        return
      }

      const isFocusInsideModal = this.$refs.container.contains(document.activeElement)

      // Bring back focus on the target
      if (this.previousActiveElement && (document.activeElement === document.body || isFocusInsideModal)) {
        this.previousActiveElement.focus()
      }
    })
  }