is returned, else falsy is returned. */
  const findParentWithClass = function(e, className){
    while(e && !e.classList.contains(className)){
      e = e.parentNode;
    }
    return e;
  };

  /** To be passed each MessageWidget's top-level DOM element
      after initial processing of the message, to set up
      hashtag and numtag references. */
  const setupHashtags = function f(elem){
    if(!f.$clickTag){
      f.$clickTag = function(ev){
        /* Click handler for hashtags */
        const tag = ev.target.dataset.hashtag;
        if(tag){
          Chat.setHashtagFilter(
            tag===Chat.filter.hashtag.activeTag
              ? false : tag
          );

              const state = {msgId: p.dataset.msgid};
              Chat.numtagHistoryStack.push(p.dataset.msgid);
              const rc = window.history.pushState(state, "");
              //console.debug("Pushing history for msgid", state);
              //console.debug("Chat.numtagHistoryStack =",Chat.numtagHistoryStack);
            }
          }else{
            Chat.submitSearch('#'+tag);
          }
        }
      };
    }
    elem.querySelectorAll('[data-hashtag]').forEach(function(e){
      e.dataset.hashtag = e.dataset.hashtag.toLowerCase();
      e.addEventListener('click', f.$clickTag, false);
    })
    elem.querySelectorAll('[data-numtag]').forEach(
      (e)=>e.addEventListener('click', f.$clickNum, false)
    )
  }/*setupHashtags()*/;

  /** Returns the first .message-widget element in DOM element

        const theMsg = findMessageWidgetParent(ev.target);
        if(theMsg) f.popup.show(theMsg);
      }/*_handleLegendClicked()*/
    }/*MessageWidget.prototype*/;
    /** Assumes that e is a MessageWidget element, ensures that
        Chat.e.viewMessages is visible, scrolls the message,
        and animates it a bit to make it more visible. */
    ctor.scrollToMessageElem = function(e){
      if(e.firstElementChild){
        Chat.setCurrentView(Chat.e.viewMessages);
        e.scrollIntoView(false);
        Chat.animate(e, 'anim-fade-out-in');
      }
    };
    return ctor;

      D.append(e, "Enter search terms in the message field. "+
               "Use #NNNNN to search for the message with ID NNNNN.");
    }
    return e;
  };
  Chat.clearSearch(true);
  /**
     Submits a history search using either its argument or the the
     main input field's current text.
  */
  Chat.submitSearch = function(term){
    Chat.setCurrentView(Chat.e.viewSearch);
    if(!arguments.length) term = this.inputValue(true);
    const eMsgTgt = this.clearSearch(true);
    if( !term ) return;
    D.append( eMsgTgt, "Searching for ",term," ...");
    const fd = new FormData();
    fd.set('q', term);
    F.fetch(
      "chat-query", {