Monday, November 17, 2014

Touch Screen Scroll Effect



function TouchScroll() {
 var instance = this;
    var Event = {
        CHANGE: 'change',
        COMPLETE: 'complete',
        ERROR: 'error',
        TOUCH_START: 'touchstart',
        TOUCH_MOVE: 'touchmove',
        TOUCH_END: 'touchend',
        MOUSE_DOWN: 'mousedown',
        MOUSE_MOVE: 'mousemove',
        MOUSE_UP: 'mouseup'
    };
 this.options = {
  'element': null
 };
 var drag = false;
 var startevent = {};
 var startpercentage = {};
 var axis = 'y';
 var target;
 this.load = function(data) {
  for (var item in data) {this.options[item] = data[item];}
  addListeners();
  setupAnimation();
 }
 function setupAnimation() {
  window.requestAnimFrame = (function() {
   return  window.requestAnimationFrame       || 
   window.webkitRequestAnimationFrame || 
   window.mozRequestAnimationFrame    || 
   window.oRequestAnimationFrame      || 
   window.msRequestAnimationFrame     || 
   function(callback, element) {window.setTimeout(callback, 1000 / 60);};
  })();
 }
 function addListeners() {
  if (instance.options.element.addEventListener) {
   instance.options.element.addEventListener(Event.MOUSE_DOWN, onTouchStart, false);
   instance.options.element.addEventListener(Event.MOUSE_MOVE, onTouchMove, false);
   instance.options.element.addEventListener(Event.MOUSE_UP, onTouchEnd, false);
   instance.options.element.addEventListener(Event.TOUCH_START, onTouchStart, false);
   instance.options.element.addEventListener(Event.TOUCH_MOVE, onTouchMove, false);
   instance.options.element.addEventListener(Event.TOUCH_END, onTouchEnd, false);
  }
 }
 function onTouchStart(e) {
  drag = true;
  target = instance.options.element || e.target;
  startevent = e;
  startpercentage = {x: (e.x/window.innerWidth)*100, y: (e.y/window.innerHeight)*100}
  //console.log('onTouchStart', e, target);
  e.preventDefault();
 }
 function onTouchMove(e) {
  if (drag == true) {
   var diffx = (startevent.pageX-e.pageX);
   var diffy = (startevent.pageY-e.pageY);
   target.scrollLeft += diffx;
   target.scrollTop += diffy;
   
   if (Math.abs(diffx) > 60) {axis = 'x';}
   else if (Math.abs(diffy) > 100) {axis = 'y';}

   //console.log('onTouchMove', target, diffx, diffy);
   e.preventDefault();
  }
 }
 function onTouchEnd(e) {
  drag = false;

  var endpercentage = {x: (e.x/window.innerWidth)*100, y: (e.y/window.innerHeight)*100}
  var diffpercentagex = -(endpercentage.x-startpercentage.x);
  var diffpercentagey = -(endpercentage.y-startpercentage.y);
  
  var diffx = (window.innerWidth/100)*diffpercentagex;
  var diffy = (window.innerHeight/100)*diffpercentagey;
  
  //console.log('onTouchEnd', e, diffpercentagex, diffpercentagey);
  
  //animate();
  
  scrollAxis(diffx*1.5, diffy*1.5, axis);
  
  e.preventDefault();
 }
 function animate() {
  requestAnimFrame(animate);
  console.log('animate');
 }
 function scrollAxis(diffx, diffy, axis) {
  var x = target.scrollLeft;
  var y = target.scrollTop;
  var start = y;
  var stop = start+diffy;
  if (axis == 'x') {
   start = x;
   stop = start+diffx;
  }
  
  var distance = stop > start ? stop - start : start - stop;
  if (distance < 50) {
   if (axis == 'x') { instance.updatePosition(stop, y); }
   else { instance.updatePosition(x, stop); }
   return;
  }
  var speedY = Math.round(distance);
  if (speedY >= 20) speedY = 20;
  var step = Math.round(distance / 30);
  var leapY = stop > start ? start + step : start - step;
  var timer = 0;
  //console.log(axis, distance, target, start, stop);
  if (stop > start) {
   for ( var i=start; i<stop; i+=step ) {
    if (axis == 'x') { setTimeout("touchscroll.updatePosition("+leapY+", 0)", timer*speedY); }
    else { setTimeout("touchscroll.updatePosition(0, "+leapY+")", timer*speedY); }
    leapY += step;
    if (leapY > stop) leapY = stop;
    timer++;
   }
   return;
  }
  for ( var i=start; i>stop; i-=step ) {
   if (axis == 'x') { setTimeout("touchscroll.updatePosition("+leapY+", 0)", timer*speedY); }
   else { setTimeout("touchscroll.updatePosition(0, "+leapY+")", timer*speedY); }
   leapY -= step;
   if (leapY < stop) leapY = stop;
   timer++;
  }
 }
 this.updatePosition = function(x, y) {
  //console.log('window.scrollTo', x, y);
  target.scrollLeft = x;
  target.scrollTop = y;
 }
}
TouchScroll.prototype = new TouchScroll();

var touchscroll = new TouchScroll();
touchscroll.load({
    'element': document.getElementsByTagName('body')[0]
});


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