text: const Consts = {
      DEFAULT_DPI: 100,
      TEXT_CURSOR_MODE: null,
      GRAB_CURSOR_MODE: null,
  
      SET_CURSOR_MODE_ACTION: null,
      ERROR_ACTION: null,
      CLOSE_MODAL_WINDOW_ACTION: null,
      CREATE_DOCUMENT_FROM_ARRAY_BUFFER_ACTION: null,
      CONTENTS_IS_GOTTEN_ACTION: null,
      ARRAY_BUFFER_LOADED_ACTION: null,
      IMAGE_DATA_RECEIVED_ACTION: null,
      DOCUMENT_CREATED_ACTION: null,
      SET_NEW_PAGE_NUMBER_ACTION: null,
      SET_PAGE_BY_URL_ACTION: null,
      //DATA_URL_CREATED_ACTION: null,
      TOGGLE_FULL_PAGE_VIEW_ACTION: null,
      PAGE_TEXT_FETCHED_ACTION: null,
      SET_USER_SCALE_ACTION: null,
      START_FILE_LOADING_ACTION: null,
      END_FILE_LOADING_ACTION: null,
      FILE_LOADING_PROGRESS_ACTION: null,
      SAVE_DOCUMENT_ACTION: null,
      SHOW_HELP_WINDOW_ACTION: null,
      CLOSE_HELP_WINDOW_ACTION: null,
      CLOSE_DOCUMENT_ACTION: null,
      SET_PAGE_ROTATION_ACTION: null,
      PAGE_ERROR_ACTION: null,
      PAGE_IS_LOADED_ACTION: null,
      PAGES_SIZES_ARE_GOTTEN: null,
      DROP_PAGE_ACTION: null,
      DROP_ALL_PAGES_ACTION: null,
      ENABLE_CONTINUOUS_SCROLL_MODE_ACTION: null,
      ENABLE_SINGLE_PAGE_MODE_ACTION: null,
      ENABLE_TEXT_MODE_ACTION: null,
      OPTIONS_UPDATED_ACTION: null,
  
      SET_API_CALLBACK_ACTION: null, // A special action for interaction with sagas. Used for program API of the viewer, look at the DjVuViewer.js
  };
  
  export function constant(obj) {
      for (const key in obj) {
          if (obj[key] === null) {
              obj[key] = key;
          }
      }
      return Object.freeze(obj);
  }
  
  export default constant(Consts);