//=====================================================        

//by default do not automatically advance in either direction

var autoNext = 0;

var autoPrev = 0;



//default advance delay is half a second

var autoAdavanceDelay = 500;

var timerID = -1;

//=====================================================        

function keyHeldEvent()

{

  //If the user has since relesaed the 2nd button that was pressed, but the primary

  //button is still held, reset its value to 1 so it can still have an effect

  if( autoNext == 2 && autoPrev == 0)

    autoNext = 1;

  if( autoPrev == 2 && autoNext == 0)

    autoPrev = 1;



  //auto advance

  if( autoNext == 1)

      nextImage();

  else if( autoPrev == 1 )

      previousImage();



  //wait delay period, then check again  

  if( autoNext == 1 || autoPrev == 1 )

   timerID = setTimeout("keyHeldEvent()", autoAdavanceDelay);

}

//=====================================================        

//Handle key release event

function keyUpEvent(key) 

{

  if (!key) 

  {

    key = event;

    key.which = key.keyCode;

  }

  switch (key.which) 

  {

    case 37: // leftkey

      autoPrev = 0;

      break;

    case 39: // rightkey

      autoNext = 0;

      break;

  }

}

//=====================================================        

//Handle key pressed by changing the current photo as appropriate

function keyDownEvent(key) 

{

  clearTimeout(timerID);



  if (!key) 

  {

    key = event;

    key.which = key.keyCode;

  }

  switch (key.which) 

  {

    case 36: // home

      firstImage()

      break;

    case 35: // end

      lastImage()

      break;

    case 37: // leftkey

      previousImage();

      autoPrev = 1;

      //if right/down key still pressed, degrade it but remember it's being held. this

      if( autoNext == 1 ) autoNext = 2;

      break;

    case 39: // rightkey

      nextImage(); 

      autoNext = 1; 

      //if left/up key still pressed, degrade it but remember it's being held. this

      if( autoPrev == 1 ) autoPrev = 2;

      break;

  }

  

  //wait delay period, then check if keys still held  

  if( autoNext == 1 || autoPrev == 1 )

    timerID = setTimeout("keyHeldEvent()", autoAdavanceDelay);

}

//=====================================================        

//Define and set startup function in order to install key handlers

function startup() 

{

  var isOp = navigator.userAgent.indexOf('Opera') > -1 ? 1 : 0;

  if (!isOp) document.onkeydown = keyDownEvent;

  if (!isOp) document.onkeyup   = keyUpEvent;

}



window.onload = startup;

//=====================================================        

//Functions for showing and hiding div elements, used to show popups

function showElement(ID)

{  document.getElementById(ID).style.visibility = "visible"; }



function hideElement(ID)

{ document.getElementById(ID).style.visibility = "hidden"; }

//=====================================================