/**
 * drag.js:
 *
 * Adapted from "JavaScript: The Definitive Guide, Fourth Edition".
 *
 * beginDrag() is designed to be called from an onmousedown event handler.
 * elementToDrag may be the element that received the mousedown event, or it
 * may be some containing element.  event must be the Event object for the
 * mousedown event.  This implementation works with both the DOM Level 2
 * event model and the IE Event model.
 **/
function beginDrag(elementToDrag, event) {
    // Compute the distance between the upper-left corner of the element
    // and the mouse click. The moveHandler function below needs these values.
    var deltaX = event.clientX - parseInt(elementToDrag.style.left);
    var deltaY = event.clientY - parseInt(elementToDrag.style.top);

    // Register the event handlers that will respond to the mousemove events
    // and the mouseup event that follow this mousedown event.
    if (document.addEventListener) {  // DOM Level 2 Event Model
	// Register capturing event handlers
        document.addEventListener("mousemove", moveHandler, true);
	document.addEventListener("mouseup", upHandler, true);
    }
    else if (document.attachEvent) {  // IE 5+ Event Model
	// In the IE Event model, we can't capture events, so these handlers
	// are triggered when only if the event bubbles up to them.
	// This assumes that there aren't any intervening elements that
	// handle the events and stop them from bubbling.
	document.attachEvent("onmousemove", moveHandler);
	document.attachEvent("onmouseup", upHandler);
    }

    // We've handled this event.  Don't let anybody else see it.
    if (event.stopPropagation) event.stopPropagation();   // DOM Level 2
    else event.cancelBubble = true;                       // IE

    // Now prevent any default action.
    if (event.preventDefault) event.preventDefault();     // DOM Level 2
    else event.returnValue = false;                       // IE

    /**
     * This is the handler that captures mousemove events when an element
     * is being dragged.  It is responsible for moving the element.
     **/
    function moveHandler(e) {
	if (!e) e = window.event;  // IE event model

        // Move the element to the current mouse position, adjusted as
	// necessary by the offset of the initial mouse click.
	elementToDrag.style.left = (e.clientX - deltaX) + "px";
	elementToDrag.style.top = (e.clientY - deltaY) + "px";

	// And don't let anyone else see this event.
	if (e.stopPropagation) e.stopPropagation();       // DOM Level 2
	else e.cancelBubble = true;                       // IE

        // Now prevent any default action.
        if (e.preventDefault) e.preventDefault();     // DOM Level 2
        else e.returnValue = false;                       // IE
    }

    /**
     * This is the handler that captures the final mouseup event that
     * occurs at the end of a drag.
     **/
    function upHandler(e) {
	if (!e) e = window.event;  // IE event model

	// Unregister the capturing event handlers.
	if (document.removeEventListener) {    // DOM Event Model
	    document.removeEventListener("mouseup", upHandler, true);
	    document.removeEventListener("mousemove", moveHandler, true);
	}
	else if (document.detachEvent) {       // IE 5+ Event Model
	    document.detachEvent("onmouseup", upHandler);
	    document.detachEvent("onmousemove", moveHandler);
	}

	// And don't let the event propagate any further.
	if (e.stopPropagation) e.stopPropagation();       // DOM Level 2
	else e.cancelBubble = true;                       // IE
    }
}















//*****************************************************************************
// Do not remove this notice.
//
// Copyright 2001 by Mike Hall.
// See http://www.brainjar.com for terms of use.
//*****************************************************************************

// Determine browser and version.

function Browser() {

  var ua, s, i;

  this.isIE    = false;
  this.isNS    = false;
  this.version = null;

  ua = navigator.userAgent;

  s = "MSIE";
  if ((i = ua.indexOf(s)) >= 0) {
	this.isIE = true;
	this.version = parseFloat(ua.substr(i + s.length));
	return;
  }

  s = "Netscape6/";
  if ((i = ua.indexOf(s)) >= 0) {
	this.isNS = true;
	this.version = parseFloat(ua.substr(i + s.length));
	return;
  }

  // Treat any other "Gecko" browser as NS 6.1.

  s = "Gecko";
  if ((i = ua.indexOf(s)) >= 0) {
	this.isNS = true;
	this.version = 6.1;
	return;
  }
}

var browser = new Browser();

// 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 {
	if (browser.isIE)
	  dragObj.elNode = window.event.srcElement;
	if (browser.isNS)
	  dragObj.elNode = event.target;

	// 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.

  if (browser.isIE) {
	x = window.event.clientX + document.documentElement.scrollLeft
	  + document.body.scrollLeft;
	y = window.event.clientY + document.documentElement.scrollTop
	  + document.body.scrollTop;
  }
  if (browser.isNS) {
	x = event.clientX + window.scrollX;
	y = event.clientY + window.scrollY;
  }

  // Save starting positions of cursor and element.

  dragObj.cursorStartX = x;
  dragObj.cursorStartY = y;
  dragObj.elStartLeft  = parseInt(dragObj.elNode.style.left, 10);
  dragObj.elStartTop   = parseInt(dragObj.elNode.style.top,  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.

  if (browser.isIE) {
	document.attachEvent("onmousemove", dragGo);
	document.attachEvent("onmouseup",   dragStop);
	window.event.cancelBubble = true;
	window.event.returnValue = false;
  }
  if (browser.isNS) {
	document.addEventListener("mousemove", dragGo,   true);
	document.addEventListener("mouseup",   dragStop, true);
	event.preventDefault();
  }
}

function dragGo(event) {

  var x, y;

  // Get cursor position with respect to the page.

  if (browser.isIE) {
	x = window.event.clientX + document.documentElement.scrollLeft
	  + document.body.scrollLeft;
	y = window.event.clientY + document.documentElement.scrollTop
	  + document.body.scrollTop;
  }
  if (browser.isNS) {
	x = event.clientX + window.scrollX;
	y = event.clientY + window.scrollY;
  }

  // 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";

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

function dragStop(event) {

  // Stop capturing mousemove and mouseup events.

  if (browser.isIE) {
	document.detachEvent("onmousemove", dragGo);
	document.detachEvent("onmouseup",   dragStop);
  }
  if (browser.isNS) {
	document.removeEventListener("mousemove", dragGo,   true);
	document.removeEventListener("mouseup",   dragStop, true);
  }
}