deficiencies in Safari.
  */
  Chat.MessageWidget = (function(){
    /**
       Constructor. If passed an argument, it is passed to
       this.setMessage() after initialization.
    */
    const cf = function(){
    const ctor = function(){
      this.e = {
        body: D.addClass(D.div(), 'message-widget'),
        tab: D.addClass(D.div(), 'message-widget-tab'),
        content: D.addClass(D.div(), 'message-widget-content')
      };
      D.append(this.e.body, this.e.tab, this.e.content);
      this.e.tab.setAttribute('role', 'button');

      3: "Wednesday", 4: "Thursday", 5: "Friday",
      6: "Saturday"
    };
    /* Given a Date, returns the timestamp string used in the "tab"
       part of message widgets. If longFmt is true then a verbose
       format is used, else a brief format is used. The returned string
       is in client-local time. */
    const theTime = function(d, longFmt=true){
    const theTime = function(d, longFmt=false){
      const li = [];
      if( longFmt ){
        //li.push( d.toISOString() );
        li.push(
          d.getFullYear(),
          '-', pad2(d.getMonth()+1/*sigh*/),
          '-', pad2(d.getMonth()+1),
          '-', pad2(d.getDate()),
          ' ',
          d.getHours(), ":",
          (d.getMinutes()+100).toString().slice(1,3)
        );
      }else{
        li.push(

       Returns true if this page believes it can embed a view of the
       file wrapped by the given message object, else returns false.
    */
    const canEmbedFile = function f(msg){
      if(!f.$rx){
        f.$rx = /\.((html?)|(txt)|(md)|(wiki)|(pikchr))$/i;
        f.$specificTypes = [
          /* Mime types we know we can embed, sans image/... */
          'text/plain',
          'text/html',
          'text/x-markdown',
          /* Firefox sends text/markdown when uploading .md files */
          'text/markdown',
          'text/x-pikchr',
          'text/x-fossil-wiki'
          // add more as we discover which ones Firefox won't
          // force the user to try to download.
          /* Add more as we discover which ones Firefox won't
             force the user to try to download. */
        ];
      }
      if(msg.fmime){
        if(msg.fmime.startsWith("image/")
           || f.$specificTypes.indexOf(msg.fmime)>=0){
          return true;
        }
      }
      return (msg.fname && f.$rx.test(msg.fname));
    };

    /**
      Returns true if the given message object "should"
      be embedded in fossil-rendered form instead of
      raw content form. This is only intended to be passed
      message objects for which canEmbedFile() returns true.
    */
    const shouldWikiRenderEmbed = function f(msg){
    const shouldFossilRenderEmbed = function f(msg){
      if(!f.$rx){
        f.$rx = /\.((md)|(wiki)|(pikchr))$/i;
        f.$specificTypes = [
          'text/x-markdown',
          'text/markdown' /* Firefox-uploaded md files */,
          'text/x-pikchr',
          'text/x-fossil-wiki'
          // add more as we discover which ones Firefox won't
          // force the user to try to download.
        ];
      }
      if(msg.fmime){
        if(f.$specificTypes.indexOf(msg.fmime)>=0) return true;
      }
      return msg.fname && f.$rx.test(msg.fname);
    };

        if(isHidden) D.removeClass(iframe, 'hidden');
        iframe.style.maxHeight = iframe.style.height
          = iframe.contentWindow.document.documentElement.scrollHeight + 'px';
        if(isHidden) D.addClass(iframe, 'hidden');
      }
    };

    cf.prototype = {
    ctor.prototype = {
      scrollIntoView: function(){
        this.e.content.scrollIntoView();
      },
      setMessage: function(m){
        const ds = this.e.body.dataset;
        ds.timestamp = m.mtime;
        ds.lmtime = m.lmtime;

        D.clearElement(this.e.tab);
        var contentTarget = this.e.content;
        var eXFrom /* element holding xfrom name */;
        if(m.xfrom){
          eXFrom = D.append(D.addClass(D.span(), 'xfrom'), m.xfrom);
          const wrapper = D.append(
            D.span(), eXFrom,
            ' ',
            D.append(D.addClass(D.span(), 'msgid'),
            D.text(" #",(m.msgid||'???'),' ',theTime(d)))
                     '#' + (m.msgid||'???')),
            (m.isSearchResult ? ' ' : ' @ '),
            D.append(D.addClass(D.span(), 'timestamp'),
                     theTime(d,!!m.isSearchResult))
          );
          D.append(this.e.tab, wrapper);
        }else{/*notification*/
          D.addClass(this.e.body, 'notification');
          if(m.isError){
            D.addClass([contentTarget, this.e.tab], 'error');
          }
          D.append(
            this.e.tab,
            D.append(D.code(), 'notification @ ',theTime(d))
            D.append(D.code(), 'notification @ ',theTime(d,false))
          );
        }
        if( m.xfrom && m.fsize>0 ){
          if( m.fmime
              && m.fmime.startsWith("image/")
              && Chat.settings.getBool('images-inline',true)
            ){

              "(" + m.fname + " " + m.fsize + " bytes)"
            )
            D.attr(a,'target','_blank');
            D.append(w, a);
            if(canEmbedFile(m)){
              /* Add an option to embed HTML attachments in an iframe. The primary
                 use case is attached diffs. */
              const shouldWikiRender = shouldWikiRenderEmbed(m);
              const downloadArgs = shouldWikiRender ? '?render' : '';
              const shouldFossilRender = shouldFossilRenderEmbed(m);
              const downloadArgs = shouldFossilRender ? '?render' : '';
              D.addClass(contentTarget, 'wide');
              const embedTarget = this.e.content;
              const self = this;
              const btnEmbed = D.attr(D.checkbox("1", false), 'id',
                                      'embed-'+ds.msgid);
              const btnLabel = D.label(btnEmbed, shouldWikiRender
              const btnLabel = D.label(btnEmbed, shouldFossilRender
                                       ? "Embed (fossil-rendered)" : "Embed");
              /* Maintenance reminder: do not disable the toggle
                 button while the content is loading because that will
                 cause it to get stuck in disabled mode if the browser
                 decides that loading the content should prompt the
                 user to download it, rather than embed it in the
                 iframe. */

            }
          }/*f.popup*/;
        }/*end static init*/
        const theMsg = findMessageWidgetParent(ev.target);
        if(theMsg) f.popup.show(theMsg);
      }/*_handleLegendClicked()*/
    };
    return cf;
    return ctor;
  })()/*MessageWidget*/;

  /**
     A widget for loading more messages (context) around a /chat-query
     result message.
  */
  Chat.SearchCtxLoader = (function(){
    const nMsgContext = 5;
    const zUpArrow = '\u25B2';
    const zDownArrow = '\u25BC';
    const cf = function(o){
    const ctor = function(o){

      /* iFirstInTable:
      **   msgid of first row in chatfts table.
      **
      ** iLastInTable:
      **   msgid of last row in chatfts table.
      **

      const ms = this;
      this.e.up.addEventListener('click', ()=>ms.load_messages(false));
      this.e.down.addEventListener('click', ()=>ms.load_messages(true));
      this.e.all.addEventListener('click', ()=>ms.load_messages( (ms.o.iPrevId==0) ));
      this.set_button_visibility();
    };

    cf.prototype = {
    ctor.prototype = {
      set_button_visibility: function() {
        if( !this.e ) return;
        const o = this.o;

        const iPrevId = (o.iPrevId!=0) ? o.iPrevId : o.iFirstInTable-1;
        const iNextId = (o.iNextId!=0) ? o.iNextId : o.iLastInTable+1;
        let nDiff = (iNextId - iPrevId) - 1;

            ms.set_button_visibility();
            ms.bIgnoreClick = false;
          }
        });
      }
    };

    return cf;
    return ctor;
  })() /*SearchCtxLoader*/;

  const BlobXferState = (function(){
    /* State for paste and drag/drop */
    const bxs = {
      dropDetails: document.querySelector('#chat-drop-details'),
      blob: undefined,

      "chat-query", {
        urlParams: {q: term},
        responseType: 'json',
        onload:function(jx){
          let previd = 0;
          D.clearElement(eMsgTgt);
          jx.msgs.forEach((m)=>{
            m.isSearchResult = true;
            const mw = new Chat.MessageWidget(m);
            const spacer = new Chat.SearchCtxLoader({
              first: jx.first,
              last: jx.last,
              previd: previd,
              nextid: m.msgid
            });