private void initialize(Region overlay) {
    if (!isInitialized() && overlay.getWidth() > 0 && overlay.getHeight() > 0) {
      setInitialized(true);
      if (!Objects.isNull(getOnInitialized())) {
        getOnInitialized().handle(new Event(overlay, overlay, Event.ANY));
      }
    }
  }
Initializes a new <b>animated</b> overlay.

@param overlay to be shown as the main content node
@param glassPane to be shown in the background of the overlay
@param animationStart animation that should be played when the overlay is being shown
@param animationEnd animation that should be played when the overlay is being hidden
workbenchfx-core/src/main/java/com/dlsc/workbenchfx/model/WorkbenchOverlay.java