var Drag = {
  
      // The current element being dragged
      obj: null,
  
      // The initalization function for the drag object
      // o = The element to act as the drag handle
      // oRoot = The element to be dragged, if not specified, 
      //               the handle will be the element dragged.
      // minX, maxX, minY, maxY = The min and max coordinates allowed for the element
      // bSwapHorzRef = Toggle the horizontal coordinate system
      // bSwapVertRef = Toggle the vertical coordinate system
      // fxMapper, fyMapper =  Functions for mapping x and y coordinates to others
      init: function(o, oRoot, minX, maxX, minY, 
              maxY, bSwapHorzRef, bSwapVertRef, fXMapper, fYMapper) {
  
          // Watch for the drag event to start
          o.onmousedown = Drag.start;
  
          // Figure out which coordinate system is being used
          o.hmode = bSwapHorzRef ? false : true ;
          o.vmode = bSwapVertRef ? false : true ;
  
          // Figure out which element is acting as the draggable ‘handle’
          o.root = oRoot && oRoot != null ? oRoot : o ;
  
          // Initalize the specified coordinate system
          if (o.hmode && isNaN(parseInt(o.root.style.left ))) o.root.style.left   = "0px";
          if (o.vmode && isNaN(parseInt(o.root.style.top ))) o.root.style.top    = "0px";
          if (!o.hmode && isNaN(parseInt(o.root.style.right ))) o.root.style.right  = "0px";
          if (!o.vmode && isNaN(parseInt(o.root.style.bottom))) o.root.style.bottom = "0px";
  
          // Look to see if the user provided min/max x/y coordinates
          o.minX = typeof minX != 'undefined' ? minX : null;
          o.minY = typeof minY != 'undefined' ? minY : null;
          o.maxX = typeof maxX != 'undefined' ? maxX : null;
          o.maxY = typeof maxY != 'undefined' ? maxY : null;
  
          // Check for any specified x and y coordinate mappers
          o.xMapper = fXMapper ? fXMapper : null;
          o.yMapper = fYMapper ? fYMapper : null;
  
          // Add shells for all the user-defined functions
          o.root.onDragStart = new Function();
          o.root.onDragEnd  = new Function();
          o.root.onDrag = new Function();
  
      },
  
      start: function(e) {
          // Figure out the object that’s being dragged
          var o = Drag.obj = this;
  
          // Normalize the event object
          e = Drag.fixE(e);
  
          // Get the current x and y coordinates
          var y = parseInt(o.vmode ? o.root.style.top  : o.root.style.bottom);
          var x = parseInt(o.hmode ? o.root.style.left : o.root.style.right );
  
          // Call the user’s function with the current x and y coordinates
          o.root.onDragStart(x, y);
  
          // Remember the starting mouse position
          o.lastMouseX = e.clientX;
          o.lastMouseY = e.clientY;
  
          // If we’re using the CSS coordinate system
          if (o.hmode) {
              // set the min and max coordiantes, where applicable
              if (o.minX != null) o.minMouseX    = e.clientX - x + o.minX;
              if (o.maxX != null) o.maxMouseX    = o.minMouseX + o.maxX - o.minX;
  
          // Otherwise, we’re using a traditional mathematical coordinate system
          } else {
              if (o.minX != null) o.maxMouseX = -o.minX + e.clientX + x;
              if (o.maxX != null) o.minMouseX = -o.maxX + e.clientX + x;
          }
  
          // If we’re using the CSS coordinate system
          if (o.vmode) {
              // set the min and max coordiantes, where applicable
              if (o.minY != null) o.minMouseY    = e.clientY - y + o.minY;
              if (o.maxY != null) o.maxMouseY    = o.minMouseY + o.maxY - o.minY;
  
          // Otherwise, we’re using a traditional mathematical coordinate system
          } else {
              if (o.minY != null) o.maxMouseY = -o.minY + e.clientY + y;
              if (o.maxY != null) o.minMouseY = -o.maxY + e.clientY + y;
          }
  
          // Watch for ‘dragging’ and ‘drag end’ events
          document.onmousemove = Drag.drag;
          document.onmouseup = Drag.end;
  
          return false;
      },
  
      // A function to watch for all movements of the mouse during the drag event
      drag: function(e) {
          // Normalize the event object
          e = Drag.fixE(e);
  
          // Get our reference to the element being dragged
          var o = Drag.obj;
  
          // Get the position of the mouse within the window
          var ey = e.clientY;
          var ex = e.clientX;
  
          // Get the current x and y coordinates
          var y = parseInt(o.vmode ? o.root.style.top  : o.root.style.bottom);
          var x = parseInt(o.hmode ? o.root.style.left : o.root.style.right );
          var nx, ny;
  
          // If a minimum X position was set, make sure it doesn’t go past that
          if (o.minX != null) ex = o.hmode ? 
              Math.max(ex, o.minMouseX) : Math.min(ex, o.maxMouseX);
  
          // If a maximum X position was set, make sure it doesn’t go past that
          if (o.maxX != null) ex = o.hmode ? 
              Math.min(ex, o.maxMouseX) : Math.max(ex, o.minMouseX);
  
          // If a minimum Y position was set, make sure it doesn’t go past that
          if (o.minY != null) ey = o.vmode ? 
              Math.max(ey, o.minMouseY) : Math.min(ey, o.maxMouseY);
  
          // If a maximum Y position was set, make sure it doesn’t go past that
          if (o.maxY != null) ey = o.vmode ? 
              Math.min(ey, o.maxMouseY) : Math.max(ey, o.minMouseY);
  
          // Figure out the newly translated x and y coordinates
          nx = x + ((ex - o.lastMouseX) * (o.hmode ? 1 : -1));
          ny = y + ((ey - o.lastMouseY) * (o.vmode ? 1 : -1));
  
          // and translate them using an x or y mapper function (if provided)
          if (o.xMapper) nx = o.xMapper(y)
          else if (o.yMapper) ny = o.yMapper(x)
  
          // Set the new x and y coordinates onto the element
          Drag.obj.root.style[o.hmode ? "left" : "right"] = nx + "px";
          Drag.obj.root.style[o.vmode ? "top" : "bottom"] = ny + "px";
  
          // and remember  the last position of the mouse
          Drag.obj.lastMouseX = ex;
          Drag.obj.lastMouseY = ey;
  
          // Call the user’s onDrag  function with the current x and y coordinates
          Drag.obj.root.onDrag(nx, ny);
  
          return false;
      },
  
      // Function that handles the end of a drag event
      end: function() {
          // No longer watch for mouse events (as the drag is done)
          document.onmousemove = null;
          document.onmouseup = null;
  
          // Call our special onDragEnd function with the x and y coordinates
          // of the element at the end of the drag event
          Drag.obj.root.onDragEnd( 
              parseInt(Drag.obj.root.style[Drag.obj.hmode ? "left" : "right"]), 
              parseInt(Drag.obj.root.style[Drag.obj.vmode ? "top" : "bottom"]));
          // No longer watch the object for drags
          Drag.obj = null;
      },
  
      // A function for normalizes the event object
      fixE: function(e) {
          // If no event object exists, then this is IE, so provide IE’s event object
          if (typeof e == 'undefined') e = window.event;
  
          // If the layer properties aren’t set, get the values from the equivalent
          // offset properties
          if (typeof e.layerX == 'undefined') e.layerX = e.offsetX;
          if (typeof e.layerY == 'undefined') e.layerY = e.offsetY;
  
          return e;
      }
  };