// javacsript library zzln_togglelayers
//  made by Zeezeilen www.zzln.nl
//  written bij Egbert Bleyenburg
//  updated 09072004: alllayers object removed
//  remember what layer is visible
//  if another one needs to become visible, simply 
//  hide the former visible one
//  ie 5.5, mozilla 5.0 en netscape 7.1 bestendig

var domversion = null; 
var domtest = false; 
var now_visible_layer_id=''; 
// now_visible_layer_id: hierin word de id van het huidig visible layer oonthouden
// wanneer we een ander layer zichtbaar maken moet deze onzichtbaar

function testDomVersion() { 
  if (document.layers) { 
    layerRef="document.layers"; 
    styleSwitch=""; 
    argVisibility="show"; 
    screenSize = window.innerWidth; 
    domversion ="ns4"; 
  } 
  else if(document.all) { 
    layerRef="document.all"; 
    styleSwitch=".style"; 
    argVisibility="visible"; 
    screenSize = document.body.clientWidth + 18; 
    domversion ="ie4"; 
  } 
  else if(document.getElementById) { 
    layerRef="document.getElementByID"; 
    styleSwitch=".style"; 
    argVisibility="visible"; 
    domversion="dom1"; 
  } 
  else { 
    domversion="none"; 
  } 
  domtest = true; 
} 

// Domindependent function setting the layer top
/*function setLayerTop(layerName,top) { 
  if (layerName =='' ){return;}
  if(domtest) { 
    if (domversion =="none") { 
      return; 
    } 
    else if (domversion == "dom1") { 
      document.getElementById(layerName).style.top=top; 
    } 
    else { 
      eval(layerRef+'["'+layerName+'"]'+styleSwitch+'.top='+top); 
    } 
  } 
  else { 
    return; 
  } 
} 
*/

// Domindependent toggles the layer visibility on 
/*function showLayer(layerName) { 
  if (layerName =='' ){return;}
  if(domtest) { 
    if (domversion =="none") { 
      return; 
    } 
    else if (domversion == "dom1") { 
      document.getElementById(layerName).style.visibility="visible"; 
    } 
    else { 
      eval(layerRef+'["'+layerName+'"]'+styleSwitch+'.visibility="visible"'); 
    } 
  } 
  else { 
    return; 
  } 
} 
*/
// Domindependent toggles the layer visibility off 
/*function hideLayer(layerName) { 
  if (layerName =='' ){return;}//anders knalt ie eruit wanneer je leeg ding meegeeft
  if(domtest) { 
    if (domversion =="none") { 
      return; 
    } 
    else if (domversion == "dom1") { 
      document.getElementById(layerName).style.visibility="hidden"; 
    } 
    else { 
      eval(layerRef+'["'+layerName+'"]'+styleSwitch+'.visibility="hidden"'); 
    } 
  } 
  else { 
    return; 
  } 
} 
*/

// Domindependent function to manipulate style properties of a layer
function setLayerProperty(layerName, property, value) { 
  if (layerName =='' ){return;}
  if(domtest) { 
    if (domversion =="none") { 
      return; 
    } 
    else if (domversion == "dom1") { 
      eval('document.getElementById("'+layerName+'").style.'+property+'="'+value+'"'); 
    } 
    else { 
      eval(layerRef+'["'+layerName+'"]'+styleSwitch+'.'+property+'="'+value+'"'); 
    } 
  } 
  else { 
    return; 
  } 
} 



//called from the load, can be removed

function ZZLN_makeAllLayersObject(){
  // I used to make an object containing all layers here, 
  // but that is not nescessary. But the callo is made from the 
  // progrtamm that write the index pages with the info from 
  // the bellbios databse, so I kept this one
  testDomVersion();
}

function ZZLN_showLayer(layername){
  var topdoc;
  var bovenbalk=90;
  if (document.indexpage) {bovenbalk=150} 
//    showLayer(layername);
  if (now_visible_layer_id !=''){setLayerProperty(now_visible_layer_id,"visibility","hidden");	}
  setLayerProperty(layername,"visibility","visible");
//  hideLayer(now_visible_layer_id);}
  now_visible_layer_id=layername;
  if (domversion =="ns4") {bovenbalk=bovenbalk-1; if (window.pageYOffset > bovenbalk){topdoc=window.pageYOffset} else {topdoc=bovenbalk}} else {if (document.body.scrollTop > bovenbalk) {topdoc=document.body.scrollTop} else {topdoc=bovenbalk}};
  // wanneer je naar beneden bent gescrolld wil je het info layuer in beeld hebben
    setLayerProperty(layername,"top",topdoc);
//  setLayerTop(layername,topdoc);
//  if (document.allLayers[i].style) { document.allLayers[i].style.top=topdoc }else{ document.allLayers[i].top=topdoc }

}