function webViewerPresentationModeChanged(evt) {
  var active = evt.active,
      switchInProgress = evt.switchInProgress;

  PDFViewerApplication.pdfViewer.presentationModeState = switchInProgress ? _pdf_viewer.PresentationModeState.CHANGING : active ? _pdf_viewer.PresentationModeState.FULLSCREEN : _pdf_viewer.PresentationModeState.NORMAL;