/**

 * Darkens the browser screen. This will make the entire page un-clickable except for any floating divs created after this is called. Restore with enlighten().

 * @param bool Controls whether the fade should be disabled or not. aclDisableTransitionFX will override this if set to true, and fades are never fired on IE.

 * @param int When specified, represents the numeric opacity value to set the fade layer to. 1-100.

 */

var darkener_index = [];

function darken(nofade, opacVal, layerid)

{

  layerid = ( layerid ) ? layerid : 'specialLayer_darkener';

  if(IE)

    nofade = true;

  if ( !opacVal )

    opacVal = 70;

  darkener_index[layerid] = ( typeof(darkener_index[layerid]) == 'number' ) ? darkener_index[layerid] + 1 : 1;

  if(document.getElementById(layerid) && !document.getElementById(layerid).destroying)

  {

    document.getElementById(layerid).style.zIndex = getHighestZ() + 1;

    if(nofade)

    {

      changeOpac(opacVal, layerid);

      document.getElementById(layerid).style.display = 'block';

      document.getElementById(layerid).myOpacVal = opacVal;

    }

    else

    {

      if ( document.getElementById(layerid).style.display != 'none' )

      {

        var currentOpac = document.getElementById(layerid).myOpacVal;

        opacity(layerid, currentOpac, opacVal, 1000);

        document.getElementById(layerid).myOpacVal = opacVal;

      }

      else

      {

        document.getElementById(layerid).style.display = 'block';

        document.getElementById(layerid).myOpacVal = opacVal;

        opacity(layerid, 0, opacVal, 1000);

      }

    }

  }

  else if(document.getElementById(layerid) && document.getElementById(layerid).destroying)

  {

    // fade in progress - abort

    console.warn('Aborting fade');

    abortFades();

    changeOpac(opacVal, layerid);

    document.getElementById(layerid).destroying = false;

    return document.getElementById(layerid);

  }

  else

  {

    w = getWidth();

    h = getHeight();

    var thediv = document.createElement('div');

    if(IE)

      thediv.style.position = 'absolute';

    else

      thediv.style.position = 'fixed';

    if ( IE )

    {

      var top = getScrollOffset();

      thediv.style.top = String(top) + 'px';

    }

    else

    {

      thediv.style.top = '0px';

    }

    thediv.style.left = '0px';

    thediv.style.opacity = '0';

    thediv.style.filter = 'alpha(opacity=0)';

    thediv.style.backgroundColor = '#000000';

    thediv.style.width =  '100%';

    thediv.style.height = '100%';

    thediv.style.zIndex = getHighestZ() + 1;

    thediv.id = layerid;

    thediv.myOpacVal = opacVal;

    if(nofade)

    {

      thediv.style.opacity = ( parseFloat(opacVal) / 100 );

      thediv.style.filter = 'alpha(opacity=' + opacVal + ')';

      body = document.getElementsByTagName('body');

      body = body[0];

      body.appendChild(thediv);

    } else {

      body = document.getElementsByTagName('body');

      body = body[0];

      body.appendChild(thediv);

      opacity(layerid, 0, opacVal, 1000);

    }

  }

  return document.getElementById(layerid);

}

/**

 * Un-darkens the screen and re-enables clicking of on-screen controls.

 * @param bool If true, disables the fade effect. Fades are always disabled if aclDisableTransitionFX is true and on IE.

 */

function enlighten(nofade, layerid)

{

  layerid = ( layerid ) ? layerid : 'specialLayer_darkener';

  if(IE)

    nofade = true;

  darkener_index[layerid] -= 1;

  if ( darkener_index[layerid] > 0 )

    return false;

  if(document.getElementById(layerid))

  {

    if(nofade)

    {

      document.getElementById(layerid).style.display = 'none';

    }

    else

    {

      document.getElementById(layerid).destroying = true;

      var from = document.getElementById(layerid).myOpacVal;

      opacity(layerid, from, 0, 1000);

      setTimeout("var l = document.getElementById('" + layerid + "'); var b = document.getElementsByTagName('body')[0]; b.removeChild(l);", 1000);

    }

  }

  return document.getElementById(layerid);

}