//  javacsript library zzln_togglelayers
//  made by Zeezeilen www.zzln.nl (Amsterdam, The netherlands)
//  written bij Egbert Bleyenburg
//  updated 09072004: alllayers object removed
//  updated 10082005: Made DOM1 compatible
//
//  actions
//  make an invisible layer visible
//  remember what layer is visible
//  if another one needs to become visible, simply 
//  hide the former visible one, and make the requested visible
//  ie 5.5+, mozilla 5.0, firefox, en netscape 7.1+ bestendig

// minimal requirement: onload=testDomVersion();
// show a hidden layer and hide any one made visible with this function previously
// <a href="JavaScript:ZZLN_toggleLayer('over_welke_projecten_gaat_dit')">Over welke projecten gaat dit?</a>



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_toggleLayer(layername){
//    showLayer(layername);
  if (now_visible_layer_id !=''){
   // setLayerProperty(now_visible_layer_id,"visibility","hidden");
    setLayerProperty(now_visible_layer_id,"display","none");			
  }
  //setLayerProperty(layername,"visibility",argVisibility);
  setLayerProperty(layername,"display","block");  
//  hideLayer(now_visible_layer_id);}
  now_visible_layer_id=layername;

}

function ZZLN_unhideLayer(layername){
  //setLayerProperty(layername,"visibility",argVisibility);
  setLayerProperty(layername,"display","block");    
}

function ZZLN_hideLayer(layername){
//    showLayer(layername);
//setLayerProperty(layername,"visibility","hidden");	
    setLayerProperty(now_visible_layer_id,"display","none");	
}