if( m.fmime && m.fmime.startsWith("image/") ){
          let img = document.createElement("img");
          img.src = "chat-download/" + m.msgid;
          span.appendChild(img);
        }else{
          let a = document.createElement("a");
          let txt = "(" + m.fname + " " + m.fsize + " bytes)";
          a.href = window.fossil.rootPath+
            'chat-download/' + m.msgid+'/'+encodeURIComponent(m.fname);
          // ^^^ add m.fname to URL to cause downloaded file to have that name.
          a.appendChild(textNode(txt));
          span.appendChild(a);
        }
        let br = document.createElement("br");
        br.style.clear = "both";
        span.appendChild(br);
      }