/*******************************************************************************************

  dw_drag.js 
  version date Nov 2003

  This code is from Dynamic Web Coding at http://www.dyn-web.com/
  See Terms of Use at http://www.dyn-web.com/bus/terms.html
  Permission granted to use this code 
  as long as this entire notice is included.

  This code borrows heavily from Aaron Boodman's dom drag at www.youngpup.net
  
********************************************************************************************/

var dragObj = {
  supported: document.getElementById && (document.addEventListener || document.attachEvent),
  obj: null,
  zOrder: 1000,
  // a class can be attached to close box (or other elements) so mousedown on it won't trigger drag
  skipClass: "xBox",
  
  // id is that of object you mousedown on when you want to drag,
  // which may or may not be inside another element (rootID) which gets dragged
  init: function(id, rootID, x, y, minX, maxX, minY, maxY) {
    if (this.supported) {
      var o = document.getElementById(id);
      o.root = rootID? document.getElementById(rootID): o;
      o.idx = id; // used for checking in start
      //  pass x/y, set left/top inline or via script, or it gets set to 0,0
      if ( isNaN( parseInt(o.root.style.left) ) ) o.root.style.left = x? x + "px": 0 + "px"; 
      if ( isNaN( parseInt(o.root.style.top) ) )  o.root.style.top =  y? y + "px": 0 + "px";
      o.minX = minX; o.maxX = maxX; o.minY = minY; o.maxY = maxY;
      o.root.on_drag_start = function() {}
      o.root.on_drag = function() {}
      o.root.on_drag_end = function() {}
      dw_event.add( o, "mousedown", dragObj.start, false );
    }
  },
  
  start: function(e) {
    var o;
    e = dw_event.DOMit(e);
    
    // Check if moused down on an object that shouldn't trigger drag (close box, for example)
    if (e.tgt.nodeType && e.tgt.nodeType == 3) e.tgt = e.tgt.parentNode;  // text node?
    if (e.tgt.className && e.tgt.className == dragObj.skipClass ) return;
    
    if (this.idx) o = dragObj.obj = this;
    else {  // o != this for ie when using attachEvent
     while (!e.tgt.idx) e.tgt = e.tgt.parentNode;
     o = dragObj.obj = e.tgt; 
    }
    o.root.style.zIndex = dragObj.zOrder++;
    o.downX = e.clientX; o.downY = e.clientY;
    o.startX = parseInt(o.root.style.left);
    o.startY = parseInt(o.root.style.top);
    o.root.on_drag_start(o.startX, o.startY);
    dw_event.add( document, "mousemove", dragObj.drag, true );
    dw_event.add( document, "mouseup",   dragObj.end,  true );
    e.preventDefault();
  },

  drag: function(e) {
    e = e? e: window.event;
    var o = dragObj.obj; 
    // calculate new x/y values
    var nx = o.startX + e.clientX - o.downX;
    var ny = o.startY + e.clientY - o.downY;
    if ( o.minX != null ) nx = Math.max( o.minX, nx );
    if ( o.maxX != null ) nx = Math.min( o.maxX, nx );
    if ( o.minY != null ) ny = Math.max( o.minY, ny );
    if ( o.maxY != null ) ny = Math.min( o.maxY, ny );
    o.root.style.left = nx + "px"; o.root.style.top  = ny + "px";
    o.root.on_drag(nx,ny);
    return false;
  },

  end: function() {
    dw_event.remove( document, "mousemove", dragObj.drag, true );
    dw_event.remove( document, "mouseup",   dragObj.end,  true );
    if ( !dragObj.obj ) return; // avoid errors in ie if inappropriate selections
    dragObj.obj.root.on_drag_end( parseInt(dragObj.obj.root.style.left), parseInt(dragObj.obj.root.style.top) );
    dragObj.obj = null;
  }

}