// Global object to hold drag information.

var dragObj = new Object();
dragObj.zIndex = 0;


function dragStart(event, id) {

  var el;
  var x, y;

  // If an element id was given, find it. Otherwise use the element being
  // clicked on.

  if (id)
    dragObj.elNode = document.getElementById(id);
  else 
  {
    dragObj.elNode = event.target;  

    /*
    if (browser.isIE)
      dragObj.elNode = window.event.srcElement;
    */  

    // If this is a text node, use its parent element.

    if (dragObj.elNode.nodeType == 3)
      dragObj.elNode = dragObj.elNode.parentNode;
  }
	
  // Get cursor position with respect to the page.
  
  x = event.clientX + window.scrollX;
  y = event.clientY + window.scrollY;


  dragObj.cursorStartX = x;
  dragObj.cursorStartY = y;
  dragObj.elStartLeft  = parseInt(dragObj.elNode.offsetLeft, 10);
  dragObj.elStartTop   = parseInt(dragObj.elNode.offsetTop,  10);

  if (isNaN(dragObj.elStartLeft)) dragObj.elStartLeft = 0;
  if (isNaN(dragObj.elStartTop))  dragObj.elStartTop  = 0;

  // Update element's z-index.
  dragObj.elNode.style.zIndex = ++dragObj.zIndex;

  // Capture mousemove and mouseup events on the page.

  document.addEventListener("mousemove", dragGo,   true);
  document.addEventListener("mouseup",   dragStop, true);
  event.preventDefault();


  /* IE
    document.attachEvent("onmousemove", dragGo);
    document.attachEvent("onmouseup",   dragStop);
    window.event.cancelBubble = true;
    window.event.returnValue = false;
  */
}

function dragGo(event) {

  var x, y;

  // Get cursor position with respect to the page.

    x = event.clientX + window.scrollX;
    y = event.clientY + window.scrollY;
/*
  if (browser.isIE) {
    x = window.event.clientX + document.documentElement.scrollLeft
      + document.body.scrollLeft;
    y = window.event.clientY + document.documentElement.scrollTop
      + document.body.scrollTop;
  }
*/
  // Move drag element by the same amount the cursor has moved.

  dragObj.elNode.style.left = (dragObj.elStartLeft + x - dragObj.cursorStartX) + "px";
  dragObj.elNode.style.top  = (dragObj.elStartTop  + y - dragObj.cursorStartY) + "px";

  event.preventDefault();

  /*
  if (browser.isIE) {
    window.event.cancelBubble = true;
    window.event.returnValue = false;
  }
  */
}

function dragStop(event) {

  // Stop capturing mousemove and mouseup events.
  document.removeEventListener("mousemove", dragGo,   true);
  document.removeEventListener("mouseup",   dragStop, true);

  /* IE
    document.detachEvent("onmousemove", dragGo);
    document.detachEvent("onmouseup",   dragStop);
  }
  */
}

function zMeUp(event, id) {

  var el;
  var x, y;

  // If an element id was given, find it. Otherwise use the element being
  // clicked on.

  if (id)
    dragObj.elNode = document.getElementById(id);
  else 
  {
    dragObj.elNode = event.target;  

    // If this is a text node, use its parent element.

    if (dragObj.elNode.nodeType == 3)
      dragObj.elNode = dragObj.elNode.parentNode;
  }
	
  // Update element's z-index.
  dragObj.elNode.style.zIndex = ++dragObj.zIndex;

}