return (
      rect.top >= 0 &&
      rect.left >= 0 &&
      rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) &&
      rect.right <= (window.innerWidth || document.documentElement.clientWidth)
    );
  };

  const ForceResizeKludge = 0 ? function(){} : (function(){
    /* Workaround for Safari mayhem regarding use of vh CSS units....
       We tried to use vh units to set the content area size for the
       chat layout, but Safari chokes on that, so we calculate that
       height here: 85% when in "normal" mode and 95% in chat-only
       mode. Larger than ~95% is too big for Firefox on Android,
       causing the input area to move off-screen. */
    const contentArea = E1('div.content'),
          bcl = document.body.classList;
    const resized = function(){
      const wh = window.innerHeight,
            mult = bcl.contains('chat-only-mode') ? 0.95 : 0.85;
      contentArea.style.height = contentArea.style.maxHeight = (wh * mult)+"px";
      //console.debug("resized.",wh, mult, window.getComputedStyle(contentArea).maxHeight);
    };
    var doit;
    window.addEventListener('resize',function(ev){
      clearTimeout(doit);
      doit = setTimeout(resized, 100);
    }, false);
    resized();
    return resized;
  })();

  const Chat = (function(){
    const cs = {
      e:{/*map of certain DOM elements.*/
        messageInjectPoint: E1('#message-inject-point'),
        pageTitle: E1('head title'),
        loadOlderToolbar: undefined /* the load-posts toolbar (dynamically created) */,
        inputWrapper: E1("#chat-input-area"),

              holder = this.e.messagesWrapper;
        if(atEnd){
          const fe = mip.nextElementSibling;
          if(fe) mip.parentNode.insertBefore(e, fe);
          else D.append(mip.parentNode, e);
        }else{
          D.append(holder,e);
          Chat.newestMessageElem = e;
        }
        if(!atEnd && !this.isMassLoading
           && e.dataset.xfrom!==Chat.me && !isInViewport(e)){
          /* If a new non-history message arrives while the user is
             scrolled elsewhere, do not scroll to the latest
             message, but gently alert the user that a new message
             has arrived. */
          F.toast.message("New message has arrived.");
        }else if(e.dataset.xfrom===Chat.me){
          e.scrollIntoView();
        }
      },
      /** Returns true if chat-only mode is enabled. */
      isChatOnlyMode: ()=>document.body.classList.contains('chat-only-mode'),
      /**
         Enters (if passed a truthy value or no arguments) or leaves
         "chat-only" mode. That mode hides the page's header and

          document.body.scroll(0,document.body.height);
        }else{
          D.removeClass(f.elemsToToggle, 'hidden');
          D.removeClass(document.body, 'chat-only-mode');
        }
        const msg = document.querySelector('.message-widget');
        if(msg) setTimeout(()=>msg.scrollIntoView(),0);
        ForceResizeKludge();
        return this;
      },
      toggleChatOnlyMode: function(){
        return this.chatOnlyMode(!this.isChatOnlyMode());
      },
      settings:{
        get: (k,dflt)=>F.storage.get(k,dflt),

      console.error("chat error:",args);
      F.toast.error.apply(F.toast, args);
    };

    cs.getMessageElemById = function(id){
      return qs('[data-msgid="'+id+'"]');
    };

    /** Finds the last .message-widget element and returns it or
        the undefined value if none are found. */
    cs.fetchLastMessageElem = function(){
      const msgs = document.querySelectorAll('.message-widget');
      return msgs.length ? msgs[msgs.length-1] : undefined;
    };

    /**
       LOCALLY deletes a message element by the message ID or passing
       the .message-row element. Returns true if it removes an element,
       else false.
    */
    cs.deleteMessageElem = function(id){
      var e;
      if(id instanceof HTMLElement){
        e = id;
        id = e.dataset.msgid;
      }else{
        e = this.getMessageElemById(id);
      }
      if(e && id){
        D.remove(e);
        if(e===this.newestMessageElem){
          Chat.newestMessageElem = Chat.fetchLastMessageElem();
        }
        F.toast.message("Deleted message "+id+".");
      }
      return !!e;
    };

    /** Given a .message-row element, this function returns whethe the
        current user may, at least hypothetically, delete the message

    var p = fetch("chat-poll?name=" + Chat.mxMsg);
    p.then(x=>x.json())
      .then(y=>newcontent(y))
      .catch(e=>console.error(e))
    /* ^^^ we don't use Chat.reportError(e) here b/c the polling
       fails exepectedly when it times out, but is then immediately
       resumed, and reportError() produces a loud error message. */
      .finally(function(){
        if(isFirstCall){
          Chat.isMassLoading = false;
          Chat.ajaxEnd();
          setTimeout(function(){
            const m = Chat.newestMessageElem;
            if(m){
              m.scrollIntoView();
              //console.debug("Scrolling into view...",msgs[msgs.length-1]);
            }
            Chat.e.inputWrapper.scrollIntoView()
          }, 0);
        }
        poll.running=false;
      });
  }
  poll.running = false;
  poll(true);
  setInterval(poll, 1000);
  F.page.chat = Chat/* enables testing the APIs via the dev tools */;
})();

  flex: 1 1 auto/*eliminates dead no-click zones on the right*/;
}
body.chat .chat-settings-popup > span.menu-entry > input[type=checkbox] {
  cursor: inherit;
}
/** Container for the list of /chat messages. */
body.chat #chat-messages-wrapper {
  overflow: auto;
  /*max-height: 800em*//*will be re-calc'd in JS*/;
  flex: 2 1 auto;
}
body.chat div.content {
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column-reverse;
  /* ^^^^ In order to get good automatic scrolling of new messages on