// Make an HTML element fly in from the top or bottom.

// Includes inertia!

// vB, don't even try. It's GPL like the rest of Enano. I know you're jealous. >:)

var fly_in_cache = new Object();

var FI_TOP = 1;

var FI_BOTTOM = 2;

var FI_IN = 1;

var FI_OUT = 2;

var FI_UP = 1;

var FI_DOWN = 2;

// Placeholder functions, to make organization a little easier :-)

function fly_in_top(element, nofade, height_taken_care_of)

{

  return fly_core(element, nofade, FI_TOP, FI_IN, height_taken_care_of);

}

function fly_in_bottom(element, nofade, height_taken_care_of)

{

  return fly_core(element, nofade, FI_BOTTOM, FI_IN, height_taken_care_of);

}

function fly_out_top(element, nofade, height_taken_care_of)

{

  return fly_core(element, nofade, FI_TOP, FI_OUT, height_taken_care_of);

}

function fly_out_bottom(element, nofade, height_taken_care_of)

{

  return fly_core(element, nofade, FI_BOTTOM, FI_OUT, height_taken_care_of);

}

function fly_core(element, nofade, origin, direction, height_taken_care_of)

{

  if ( !element || typeof(element) != 'object' )

    return false;

  // target dimensions

  var top, left;

  // initial dimensions

  var topi, lefti;

  // current dimensions

  var topc, leftc;

  // screen dimensions

  var w = getWidth();

  var h = getHeight();

  var y = parseInt ( getScrollOffset() );

  // temp vars

  var dim, off, diff, dist, ratio, opac_factor;

  // setup element

  element.style.position = 'absolute';

  dim = [ $(element).Height(), $(element).Width() ];

  off = [ $(element).Top(), $(element).Left() ];

  if ( height_taken_care_of )

  {

    top = off[0];

    left = off[1];

  }

  else

  {

    top  = Math.round(( h / 2 ) - ( dim[0] / 2 )) + y; // - ( h / 4 ));

    left = Math.round(( w / 2 ) - ( dim[1] / 2 ));

  }

  // you can change this around to get it to fly in from corners or be on the left/right side

  lefti = left;

  // calculate first frame Y position

  if ( origin == FI_TOP && direction == FI_IN )

  {

    topi = 0 - dim[0] + y;

  }

  else if ( origin == FI_TOP && direction == FI_OUT )

  {

    topi = top;

    top = 0 - dim[0] + y;

  }

  else if ( origin == FI_BOTTOM && direction == FI_IN )

  {

    topi = h + y;

  }

  else if ( origin == FI_BOTTOM && direction == FI_OUT )

  {

    topi = top;

    top = h + y;

  }

  var abs_dir = ( ( origin == FI_TOP && direction == FI_IN ) || ( origin == FI_BOTTOM && direction == FI_OUT ) ) ? FI_DOWN : FI_UP;

  /*

   * Framestepper parameters

   */

  // starting value for inertia

  var inertiabase = 1;

  // increment for inertia, or 0 to disable inertia effects

  var inertiainc  = 1;

  // when the progress reaches this %, deceleration is activated

  var divider = 0.666667;

  // multiplier for deceleration, setting this above 2 can cause some weird slowdown effects

  var decelerate  = 2; // 1 / divider; // reciprocal of the divider

  /*

   * Timer parameters

   */

  // how long animation start is delayed, you want this at 0

  var timer = 0;

  // frame ttl

  var timestep = 12;

  // sanity check

  var frames = 0;

  // cache element so it can be changed from within setTimeout()

  var rand_seed = Math.floor(Math.random() * 1000000);

  fly_in_cache[rand_seed] = element;

  // set element left pos, you can comment this out to preserve left position

  element.style.left = left + 'px';

  element.style.top  = topi + 'px';

  if ( nofade )

  {

    domObjChangeOpac(100, element);

  }

  // total distance to be traveled

  dist = abs(top - topi);

  // animation loop

  while ( true )

  {

    // used for a sanity check

    frames++;

    // time until this frame should be executed

    timer += timestep;

    // math stuff

    // how far we are along in animation...

    diff = abs(top - topi);

    // ...in %

    ratio = abs( 1 - ( diff / dist ) );

    // decelerate if we're more than 2/3 of the way there

    if ( ratio < divider )

      inertiabase += inertiainc;

    else

      inertiabase -= ( inertiainc * decelerate );

    // if the deceleration factor is anywhere above 1 then technically that can cause an infinite loop

    // so leave this in there unless decelerate is set to 1

    if ( inertiabase < 1 )

      inertiabase = 1;

    // uncomment to disable inertia

    // inertiabase = 3;

    // figure out frame Y position

    topi = ( abs_dir == FI_UP ) ? topi - inertiabase : topi + inertiabase;

    if ( ( abs_dir == FI_DOWN && topi > top ) || ( abs_dir == FI_UP && top > topi ) )

      topi = top;

    // tell the browser to do it

    setTimeout('var o = fly_in_cache['+rand_seed+']; o.style.top=\''+topi+'px\';', timer);

    if ( !nofade )

    {

      // handle fade

      opac_factor = ratio * 100;

      if ( direction == FI_OUT )

        opac_factor = 100 - opac_factor;

      setTimeout('var o = fly_in_cache['+rand_seed+']; domObjChangeOpac('+opac_factor+', o);', timer);

    }

    // if we're done or if our sanity check failed then break out of the loop

    if ( ( abs_dir == FI_DOWN && topi >= top ) || ( abs_dir == FI_UP && top >= topi ) || frames > 1000 )

      break;

  }

  //timer += timestep;

  setTimeout('delete(fly_in_cache['+rand_seed+']);', timer);

  return timer;

}

function abs(i)

{

  if ( isNaN(i) )

    return i;

  return ( i < 0 ) ? ( 0 - i ) : i;

}