public final EventHandler<Event> getOnShown() {
    return getDialogControl().getOnShown();
  }
The dialog's action, which is invoked whenever the dialog has been fully initialized and is
being shown. Whenever the {@link DialogControl#dialogProperty()}, {@link
WorkbenchDialog#buttonTypes}, {@link DialogControl#buttonTextUppercaseProperty()} or {@link
DialogControl#workbenchProperty()} changes, the dialog will be rebuilt and upon completion, an
event will be fired.

@param value the {@link EventHandler} which will be invoked after the dialog has been
             fully initialized and is being shown
workbenchfx-core/src/main/java/com/dlsc/workbenchfx/model/WorkbenchDialog.java