var HTTPReq = new Array();

function AJAX_Initiate(control) {
  var xmlreq;
  var retval;
  try { xmlreq = new XMLHttpRequest(); }
  catch ( microslop ) {
    try { xmlreq = new ActiveXObject("Msxml2.XMLHTTP"); }
    catch ( different_microslop ) {
      try { xmlreq = new ActiveXObject("Microsoft.XMLHTTP"); }
      catch ( wont_work ) {
	xmlreq = false;
      }
    }
  }
  if ( !xmlreq )  return -1;
  retval = HTTPReq.length;
  HTTPReq[retval] = xmlreq;
  return retval;
}

function AJAX_UpdateTable(stack) {
  var Req = HTTPReq[stack];
  if ( !Req )  return;
  if ( ( Req.readyState != 4 ) || ( Req.status != 200 ) )  return;
  var rText = new String(Req.responseText);
  var lines = rText.split("\n");
  gallerystart = lines.shift();
  galleryend = lines.shift();
  for ( var n=1; n<= 4; n++ ) {
	var imgname = lines.shift();
	var ctrl = document.getElementById("img"+n);
	ctrl.src = imgname;
  }
  HTTPReq[stack] = null;
  if ( gallerystart == 0 )
	topBarOff();
  else
	topBarOn();
  if ( ( Number(gallerystart) + 4 ) >= galleryend )
	bottomBarOff();
  else
	bottomBarOn();
}

function AJAX_GetImages(startpoint) {
  var url = "photolist.php?start="+startpoint;
  var ndx = AJAX_Initiate();
  if ( ndx == -1 ) return;
  var Req = HTTPReq[ndx];
  Req.onreadystatechange = new Function("AJAX_UpdateTable("+ndx+");");
  Req.open("GET",url,true);
  Req.send("");
}