/*  functions to modify display parameters; also includes parsing of the
 *  window location search string (useful in controlling displays), and
 *  window status line control
 */

function srchParm(tgt) { // get value of search parameter
  // returns zero if not found
  var s1 = window.location.search.split("?");
  for (var i1 = 0; i1 < s1.length; i1++) {
    var s2 = s1[i1].split("&");
    for (var i2 = 0; i2 < s2.length; i2++) {
      var s3 = s2[i2].split("=");
      if (s3[0] == tgt) {
        if (s3[1]) return (s3[1]);
       } // if
    } // i2 loop
  } // i1 loop 
  return 0; // fall-through case
} // srchParm()

function chgStat(msg) {
  window.status = msg;
  return(true);
} // chgStat()

function getElmnt(id) {  // get object from ID
  var element = null;
  if (document.getElementById) {
    element = document.getElementById(id);
  } else if (document.all) {
    element = document.all[id];
  } else if (document.layers) {
    element = document.layers[id];
  } // if
  return (element);
} // getElmnt()

function chgDisp(id, valu) {  // change object display setting
  var el = getElmnt(id);
  if (el) {
    var ch = el;
    if (el.style) ch = el.style;
    ch.display = valu;
  } // if
} // chgDisp()

function chgVis(id, valu) { // change object visibility
  var el = getElmnt(id);
  if (el) {
    var ch = el;
    if (el.style) ch = el.style;
    ch.visibility = valu;
  } // if
} // chgVis()

function toglDisp(id, val) { // toggle display between given value and "none"
  var el = getElmnt(id);
  if (el) {
    var ch = el;
    if (el.style) ch = el.style;
    if (ch.display == val) {
      ch.display = "none";
      return false;
    } // if
    ch.display = val;
  } // if
  return true;
} // toglDisp()

function twistDisp(ctlImg, showImg, hideImg, id, val) {
  // toggle display and change a key image accordingly
  var sh = toglDisp(id, val);
  ctlImg.src = sh ? showImg : hideImg;
  return(sh);  
} // twistDisp()