cwarden · July 11, 2012 15:27
diff --git a/table.html b/table.html
 <html>
 <style type="text/css" media="screen">
  #table {
    position: absolute;
    top: 30px;
    bottom: 0;
    left: 10px;
    right: 10px;
  }
  #header {
    position: absolute;
    top: 0;
    height: 25px;
    left: 10px;
    right: 10px;
    font-weight: bold;
    font-size: 20px;
    border-bottom: solid 1px #444;
  }
  .title {
    width: 100px;
  }
  .desc {
    position: absolute;
    left: 120px; 
    top: 0px;
    font-family: italic;
    color: #444;
  }
 </style>
 <script type="text/javascript" charset="utf-8">
  window.ui = window.ui || {};

  /**  @constructor */
  ui.ListView = function(element, collection) {
    this.el = element;
    this.cellHeight = 30;
    this.collection = collection;

    // Find the first element with class 'Template' and use as a row template
    var tt = this.el.getElementsByClassName('Template');
    if (tt.length > 0) {
      var t = tt[0];
      this.template = t;
      t.parentNode.removeChild(t);
    }

    this.content = document.createElement('div');
    this.el.style.overflow = 'auto';
    this.el.appendChild(this.content);
    this.cells = [];
    this.listeners = [];

    // Juggle rows on scroll
    this.el.addEventListener('scroll', this.redraw.bind(this));

    // Ensure we have enough rows.
    window.addEventListener('resize', this.redraw.bind(this));

    // Get us started
    this.redraw();
  };

  /** Ensure we have enough physical lines to fill the screen */
  ui.ListView.prototype.ensure = function(desired) {
      while (this.cells.length < desired) {
        var cell = new ui.Template(this, this.template);
        cell.element.style.position = 'absolute';
        cell.element.style.y = 0;
        cell.element.style.x = 0;
        cell.element.style.height = this.cellHeight + 'px';
        cell.element.style.width = '100%';
        this.content.appendChild(cell.element);
        this.cells.push(cell);
      }
    };

  /** Rerender the rows */
  ui.ListView.prototype.redraw = function() {
    var cellh = this.cellHeight;
    var oheight = this.el.offsetHeight;
    var top = this.el.scrollTop;
    var topRow = ~~(top / cellh);
    var len = this.collection.length;

    this.content.style.height = (len * cellh) + 'px';

    var slosh = 10;

    var desiredRows = ~~(oheight / cellh + slosh);
    this.ensure(desiredRows);

    var start = Math.max(topRow - slosh / 2, 0);
    var end = Math.min(len, start + desiredRows);
    start = Math.max(0, end - desiredRows);

    var rows = [];
    for (var i = start; i < start + this.cells.length; i++) {
      rows.push(i);
      var cell = this.cells[i % this.cells.length];
      if (i < len) {
        var item = this.collection[i];
        cell.setItem(item);
        cell.setTop(cellh * i);
        cell.element.style.display = 'block';
      } else {
        cell.element.style.display = 'none';
      }
    }
  };


  /** @constructor */
  ui.Template = function(listView, node) {
    this.listView = listView;
    this.db = listView.collection;

    var tasks = [];
    this.tasks = tasks;

    this.element = node.cloneNode(true);

    // This recursive function sets up our "tasks" which fill in data from 
    function proc(node) {
      var cc = node.childNodes;
      for (var i = 0; i < cc.length; i++) {
        var child = cc[i];
        // TODO - Handle attributes and more complex text substitution.
        // e.g. sequence of "text",key extracted from '{{title}} by {{author}}' or 'http://{{key}}_{{blah}}.jpg'
        if (child.nodeType == 3) {
          var m = child.textContent.match('{{(.*)}}');
          if (m) {
            var key = m[1];
            tasks.push(function(doc) {
              child.textContent = doc[key] || '';
            });
          }
        } else {
          proc(child);
        }
      }
    }
    proc(this.element);
  };

  ui.Template.prototype.setTop = function(top) {
      this.element.style.top = top + 'px';
  };

  ui.Template.prototype.setItem = function(item) {
    if (item != this.item) {
      this.item = item;
      this.tasks.forEach(function(func) { func(item); });
    }
  };
  
  /** @constructor 
   *
   * This mixes in a touch scroll handler for iPad.  We can't use the native scrolling because it bounces the app.
   *
   * REVIEW - consider switching from overflow: auto to static positioning, so we can bounce/overflow our scrollable div.
   */
  ui.ScrollController = function(el) {
    this.el = el;
    el.addEventListener('touchstart', this.touchstart.bind(this));
    el.addEventListener('touchmove', this.touchmove.bind(this));
    el.addEventListener('touchend', this.touchend.bind(this));
  };

  ui.ScrollController.prototype = {
    touchstart: function (ev) {

      if (this.animating)
        this.endAnimation();

      td = ev;
      console.log('down',ev);
      this.y = ev.changedTouches[0].clientY;
      this.startY = this.y;

      this.pos = 0;
      this.prev = ev;

      this.pstamp = ev.timeStamp;
      this.velocity = undefined;
    },
    update: function(ev) {
      var t = ev.changedTouches[0];
      var deltaY = t.clientY - this.y;
      this.el.scrollTop -= deltaY;

      var deltaT = (ev.timeStamp - this.pstamp);
      var velocity = deltaY / deltaT;

      // weighted average
      if (this.velocity !== undefined)
        this.velocity = (2*velocity + this.velocity)/3;
      else
        this.velocity = velocity;


      this.pos = (this.pos + 1 ) % 5;
      this.prev = ev;
      this.pstamp = ev.timeStamp;

      if (this.timer)
        clearInterval(this.timer);
      this.timer = undefined;
    },
    touchmove: function (ev) {
      var t = ev.changedTouches[0];
      if (this.y) {
        if (Math.abs(t.clientY - this.startY) > 10)
          this.isScrolling = true;

        if (this.isScrolling) {
          this.update(ev);
          this.y = t.clientY;
        }
        ev.preventDefault();      

      }
      tm = ev;
    },
    touchend: function (ev) {
      tu = ev;
      this.y = undefined;

      if (this.isScrolling) {
        ev.preventDefault();

        if (!isNaN(this.velocity)) {
          this.startAnimation();
        } else {
          this.isScrolling = false;
        }

      }

      console.log('up',ev, this.pos, this.velocity, this.data);
    },
    startAnimation: function() {
      if (this.timer)
        return;
      this.animating = true;

      this.foo = Date.now();
      this.timer = setInterval(this.animate.bind(this), 10);
    },
    endAnimation: function() {
      this.animating = false;
      clearInterval(this.timer);
      this.timer = undefined;
    },
    animate: function() {
      if (!this.animating) {
        clearInterval(this.timer);
        return;
      }

      var now = Date.now();
      var deltaY = this.velocity * (now-this.foo);

      if (this.velocity > 0.02)
        this.velocity -= .02;
      else if (this.velocity < -.02)
        this.velocity += .02;


      this.el.scrollTop = ~~(this.el.scrollTop - deltaY);
      this.foo = now;

      if (Math.abs(deltaY) < 1) {
        this.endAnimation();
        this.isScrolling = false;
      }
    }
  };
  
 </script>
 <script type="text/javascript" charset="utf-8">
  // Fill in some dummy data and initialize the table.
  function initialize() {
    var data = [];
    for (var i=0;i<10000;i++) {
      data[i] = {'title': 'Title '+i, 'description': 'Description '+i};
    }
    var table = document.getElementById('table');
    // comment this out if you don't want iPad scrolling.
    new ui.ScrollController(table);
    var listView = new ui.ListView(table, data);
    
  }
 </script>
 <body onload='initialize()'>
  <div id='header' class='row'>
    <div class='title'>Title</div><div class='desc'>Description</div>
  </div>
  <div id='table'>
    <!-- This is the layout for the rows, the mustache expressions are filled in with corresponding fields from "data" -->
    <div class="Template">
      <div class='title'>{{title}}</div><div class='desc'>{{description}}</div>
    </div>
  </div>
 </body>
 </html>
	<html>
	<style type="text/css" media="screen">
	#table {
	position: absolute;
	top: 30px;
	bottom: 0;
	left: 10px;
	right: 10px;
	}
	#header {
	position: absolute;
	top: 0;
	height: 25px;
	left: 10px;
	right: 10px;
	font-weight: bold;
	font-size: 20px;
	border-bottom: solid 1px #444;
	}
	.title {
	width: 100px;
	}
	.desc {
	position: absolute;
	left: 120px;
	top: 0px;
	font-family: italic;
	color: #444;
	}
	</style>
	<script type="text/javascript" charset="utf-8">
	window.ui = window.ui \|\| {};

	/** @constructor */
	ui.ListView = function(element, collection) {
	this.el = element;
	this.cellHeight = 30;
	this.collection = collection;

	// Find the first element with class 'Template' and use as a row template
	var tt = this.el.getElementsByClassName('Template');
	if (tt.length > 0) {
	var t = tt[0];
	this.template = t;
	t.parentNode.removeChild(t);
	}

	this.content = document.createElement('div');
	this.el.style.overflow = 'auto';
	this.el.appendChild(this.content);
	this.cells = [];
	this.listeners = [];

	// Juggle rows on scroll
	this.el.addEventListener('scroll', this.redraw.bind(this));

	// Ensure we have enough rows.
	window.addEventListener('resize', this.redraw.bind(this));

	// Get us started
	this.redraw();
	};

	/** Ensure we have enough physical lines to fill the screen */
	ui.ListView.prototype.ensure = function(desired) {
	while (this.cells.length < desired) {
	var cell = new ui.Template(this, this.template);
	cell.element.style.position = 'absolute';
	cell.element.style.y = 0;
	cell.element.style.x = 0;
	cell.element.style.height = this.cellHeight + 'px';
	cell.element.style.width = '100%';
	this.content.appendChild(cell.element);
	this.cells.push(cell);
	}
	};

	/** Rerender the rows */
	ui.ListView.prototype.redraw = function() {
	var cellh = this.cellHeight;
	var oheight = this.el.offsetHeight;
	var top = this.el.scrollTop;
	var topRow = ~~(top / cellh);
	var len = this.collection.length;

	this.content.style.height = (len * cellh) + 'px';

	var slosh = 10;

	var desiredRows = ~~(oheight / cellh + slosh);
	this.ensure(desiredRows);

	var start = Math.max(topRow - slosh / 2, 0);
	var end = Math.min(len, start + desiredRows);
	start = Math.max(0, end - desiredRows);

	var rows = [];
	for (var i = start; i < start + this.cells.length; i++) {
	rows.push(i);
	var cell = this.cells[i % this.cells.length];
	if (i < len) {
	var item = this.collection[i];
	cell.setItem(item);
	cell.setTop(cellh * i);
	cell.element.style.display = 'block';
	} else {
	cell.element.style.display = 'none';
	}
	}
	};


	/** @constructor */
	ui.Template = function(listView, node) {
	this.listView = listView;
	this.db = listView.collection;

	var tasks = [];
	this.tasks = tasks;

	this.element = node.cloneNode(true);

	// This recursive function sets up our "tasks" which fill in data from
	function proc(node) {
	var cc = node.childNodes;
	for (var i = 0; i < cc.length; i++) {
	var child = cc[i];
	// TODO - Handle attributes and more complex text substitution.
	// e.g. sequence of "text",key extracted from '{{title}} by {{author}}' or 'http://{{key}}_{{blah}}.jpg'
	if (child.nodeType == 3) {
	var m = child.textContent.match('{{(.*)}}');
	if (m) {
	var key = m[1];
	tasks.push(function(doc) {
	child.textContent = doc[key] \|\| '';
	});
	}
	} else {
	proc(child);
	}
	}
	}
	proc(this.element);
	};

	ui.Template.prototype.setTop = function(top) {
	this.element.style.top = top + 'px';
	};

	ui.Template.prototype.setItem = function(item) {
	if (item != this.item) {
	this.item = item;
	this.tasks.forEach(function(func) { func(item); });
	}
	};

	/** @constructor
	*
	* This mixes in a touch scroll handler for iPad. We can't use the native scrolling because it bounces the app.
	*
	* REVIEW - consider switching from overflow: auto to static positioning, so we can bounce/overflow our scrollable div.
	*/
	ui.ScrollController = function(el) {
	this.el = el;
	el.addEventListener('touchstart', this.touchstart.bind(this));
	el.addEventListener('touchmove', this.touchmove.bind(this));
	el.addEventListener('touchend', this.touchend.bind(this));
	};

	ui.ScrollController.prototype = {
	touchstart: function (ev) {

	if (this.animating)
	this.endAnimation();

	td = ev;
	console.log('down',ev);
	this.y = ev.changedTouches[0].clientY;
	this.startY = this.y;

	this.pos = 0;
	this.prev = ev;

	this.pstamp = ev.timeStamp;
	this.velocity = undefined;
	},
	update: function(ev) {
	var t = ev.changedTouches[0];
	var deltaY = t.clientY - this.y;
	this.el.scrollTop -= deltaY;

	var deltaT = (ev.timeStamp - this.pstamp);
	var velocity = deltaY / deltaT;

	// weighted average
	if (this.velocity !== undefined)
	this.velocity = (2*velocity + this.velocity)/3;
	else
	this.velocity = velocity;


	this.pos = (this.pos + 1 ) % 5;
	this.prev = ev;
	this.pstamp = ev.timeStamp;

	if (this.timer)
	clearInterval(this.timer);
	this.timer = undefined;
	},
	touchmove: function (ev) {
	var t = ev.changedTouches[0];
	if (this.y) {
	if (Math.abs(t.clientY - this.startY) > 10)
	this.isScrolling = true;

	if (this.isScrolling) {
	this.update(ev);
	this.y = t.clientY;
	}
	ev.preventDefault();

	}
	tm = ev;
	},
	touchend: function (ev) {
	tu = ev;
	this.y = undefined;

	if (this.isScrolling) {
	ev.preventDefault();

	if (!isNaN(this.velocity)) {
	this.startAnimation();
	} else {
	this.isScrolling = false;
	}

	}

	console.log('up',ev, this.pos, this.velocity, this.data);
	},
	startAnimation: function() {
	if (this.timer)
	return;
	this.animating = true;

	this.foo = Date.now();
	this.timer = setInterval(this.animate.bind(this), 10);
	},
	endAnimation: function() {
	this.animating = false;
	clearInterval(this.timer);
	this.timer = undefined;
	},
	animate: function() {
	if (!this.animating) {
	clearInterval(this.timer);
	return;
	}

	var now = Date.now();
	var deltaY = this.velocity * (now-this.foo);

	if (this.velocity > 0.02)
	this.velocity -= .02;
	else if (this.velocity < -.02)
	this.velocity += .02;


	this.el.scrollTop = ~~(this.el.scrollTop - deltaY);
	this.foo = now;

	if (Math.abs(deltaY) < 1) {
	this.endAnimation();
	this.isScrolling = false;
	}
	}
	};

	</script>
	<script type="text/javascript" charset="utf-8">
	// Fill in some dummy data and initialize the table.
	function initialize() {
	var data = [];
	for (var i=0;i<10000;i++) {
	data[i] = {'title': 'Title '+i, 'description': 'Description '+i};
	}
	var table = document.getElementById('table');
	// comment this out if you don't want iPad scrolling.
	new ui.ScrollController(table);
	var listView = new ui.ListView(table, data);

	}
	</script>
	<body onload='initialize()'>
	<div id='header' class='row'>
	<div class='title'>Title</div><div class='desc'>Description</div>
	</div>
	<div id='table'>
	<!-- This is the layout for the rows, the mustache expressions are filled in with corresponding fields from "data" -->
	<div class="Template">
	<div class='title'>{{title}}</div><div class='desc'>{{description}}</div>
	</div>
	</div>
	</body>
	</html>