text: 	
  	d3.tip = function() {
  		var direction = d3_tip_direction,
  		   offset    = d3_tip_offset,
  		   html      = d3_tip_html,
  		   node      = initNode(),
  		   svg       = null,
  		   point     = null,
  		   target    = null
  
  		function tip(vis) {
  		 svg = getSVGNode(vis)
  		 point = svg.createSVGPoint()
  		 document.body.appendChild(node)
  		}
  
  		// Public - show the tooltip on the screen
  		//
  		// Returns a tip
  		tip.show = function() {
  		 var args = Array.prototype.slice.call(arguments)
  		 if(args[args.length - 1] instanceof SVGElement) target = args.pop()
  
  		 var content = html.apply(this, args),
  		     poffset = offset.apply(this, args),
  		     dir     = direction.apply(this, args),
  		     nodel   = d3.select(node), i = 0,
  		     coords
  
  		 nodel.html(content)
  		   .style({ opacity: 1, 'pointer-events': 'all' })
  
  		 while(i--) nodel.classed(directions[i], false)
  		 coords = direction_callbacks.get(dir).apply(this)
  		 nodel.classed(dir, true).style({
  		   top: (coords.top +  poffset[0]) + 'px',
  		   left: (coords.left + poffset[1]) + 'px'
  		 })
  
  		 return tip
  		}
  
  		// Public - hide the tooltip
  		//
  		// Returns a tip
  		tip.hide = function() {
  		 nodel = d3.select(node)
  		 nodel.style({ opacity: 0, 'pointer-events': 'none' })
  		 return tip
  		}
  
  		// Public: Proxy attr calls to the d3 tip container.  Sets or gets attribute value.
  		//
  		// n - name of the attribute
  		// v - value of the attribute
  		//
  		// Returns tip or attribute value
  		tip.attr = function(n, v) {
  		 if (arguments.length < 2 && typeof n === 'string') {
  		   return d3.select(node).attr(n)
  		 } else {
  		   var args =  Array.prototype.slice.call(arguments)
  		   d3.selection.prototype.attr.apply(d3.select(node), args)
  		 }
  
  		 return tip
  		}
  
  		// Public: Proxy style calls to the d3 tip container.  Sets or gets a style value.
  		//
  		// n - name of the property
  		// v - value of the property
  		//
  		// Returns tip or style property value
  		tip.style = function(n, v) {
  		 if (arguments.length < 2 && typeof n === 'string') {
  		   return d3.select(node).style(n)
  		 } else {
  		   var args =  Array.prototype.slice.call(arguments)
  		   d3.selection.prototype.style.apply(d3.select(node), args)
  		 }
  
  		 return tip
  		}
  
  		// Public: Set or get the direction of the tooltip
  		//
  		// v - One of n(north), s(south), e(east), or w(west), nw(northwest),
  //		     sw(southwest), ne(northeast) or se(southeast)
  		//
  		// Returns tip or direction
  		tip.direction = function(v) {
  		 if (!arguments.length) return direction
  		 direction = v == null ? v : d3.functor(v)
  
  		 return tip
  		}
  
  		// Public: Sets or gets the offset of the tip
  		//
  		// v - Array of [x, y] offset
  		//
  		// Returns offset or
  		tip.offset = function(v) {
  		 if (!arguments.length) return offset
  		 offset = v == null ? v : d3.functor(v)
  
  		 return tip
  		}
  
  		// Public: sets or gets the html value of the tooltip
  		//
  		// v - String value of the tip
  		//
  		// Returns html value or tip
  		tip.html = function(v) {
  		 if (!arguments.length) return html
  		 html = v == null ? v : d3.functor(v)
  
  		 return tip
  		}
  
  		function d3_tip_direction() { return 'n' }
  		function d3_tip_offset() { return [0, 0] }
  		function d3_tip_html() { return ' ' }
  
  		var direction_callbacks = d3.map({
  		 n:  direction_n,
  		 s:  direction_s,
  		 e:  direction_e,
  		 w:  direction_w,
  		 nw: direction_nw,
  		 ne: direction_ne,
  		 sw: direction_sw,
  		 se: direction_se
  		}),
  
  		directions = direction_callbacks.keys()
  
  		function direction_n() {
  		 var bbox = getScreenBBox()
  		 return {
  		   top:  bbox.n.y - node.offsetHeight,
  		   left: bbox.n.x - node.offsetWidth / 2
  		 }
  		}
  
  		function direction_s() {
  		 var bbox = getScreenBBox()
  		 return {
  		   top:  bbox.s.y,
  		   left: bbox.s.x - node.offsetWidth / 2
  		 }
  		}
  
  		function direction_e() {
  		 var bbox = getScreenBBox()
  		 return {
  		   top:  bbox.e.y - node.offsetHeight / 2,
  		   left: bbox.e.x
  		 }
  		}
  
  		function direction_w() {
  		 var bbox = getScreenBBox()
  		 return {
  		   top:  bbox.w.y - node.offsetHeight / 2,
  		   left: bbox.w.x - node.offsetWidth
  		 }
  		}
  
  		function direction_nw() {
  		 var bbox = getScreenBBox()
  		 return {
  		   top:  bbox.nw.y - node.offsetHeight,
  		   left: bbox.nw.x - node.offsetWidth
  		 }
  		}
  
  		function direction_ne() {
  		 var bbox = getScreenBBox()
  		 return {
  		   top:  bbox.ne.y - node.offsetHeight,
  		   left: bbox.ne.x
  		 }
  		}
  
  		function direction_sw() {
  		 var bbox = getScreenBBox()
  		 return {
  		   top:  bbox.sw.y,
  		   left: bbox.sw.x - node.offsetWidth
  		 }
  		}
  
  		function direction_se() {
  		 var bbox = getScreenBBox()
  		 return {
  		   top:  bbox.se.y,
  		   left: bbox.e.x
  		 }
  		}
  
  		function initNode() {
  		 var node = d3.select(document.createElement('div'))
  		 node.style({
  		   position: 'absolute',
  		   opacity: 0,
  		   pointerEvents: 'none',
  		   boxSizing: 'border-box'
  		 })
  
  		 return node.node()
  		}
  
  		function getSVGNode(el) {
  		 el = el.node()
  		 if(el.tagName.toLowerCase() == 'svg')
  		   return el
  
  		 return el.ownerSVGElement
  		}
  
  		// Private - gets the screen coordinates of a shape
  		//
  		// Given a shape on the screen, will return an SVGPoint for the directions
  		// n(north), s(south), e(east), w(west), ne(northeast), se(southeast), nw(northwest),
  		// sw(southwest).
  		//
  //		    +-+-+
  //		    |   |
  //		    +   +
  //		    |   |
  //		    +-+-+
  		//
  		// Returns an Object {n, s, e, w, nw, sw, ne, se}
  		function getScreenBBox() {
  		 var targetel   = target || d3.event.target,
  		     bbox       = {},
  		     matrix     = targetel.getScreenCTM(),
  		     tbbox      = targetel.getBBox(),
  		     width      = tbbox.width,
  		     height     = tbbox.height,
  		     x          = tbbox.x,
  		     y          = tbbox.y,
  		     scrollTop  = document.documentElement.scrollTop || document.body.scrollTop,
  		     scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft
  
  
  		 point.x = x + scrollLeft
  		 point.y = y + scrollTop
  		 bbox.nw = point.matrixTransform(matrix)
  		 point.x += width
  		 bbox.ne = point.matrixTransform(matrix)
  		 point.y += height
  		 bbox.se = point.matrixTransform(matrix)
  		 point.x -= width
  		 bbox.sw = point.matrixTransform(matrix)
  		 point.y -= height / 2
  		 bbox.w  = point.matrixTransform(matrix)
  		 point.x += width
  		 bbox.e = point.matrixTransform(matrix)
  		 point.x -= width / 2
  		 point.y -= height / 2
  		 bbox.n = point.matrixTransform(matrix)
  		 point.y += height
  		 bbox.s = point.matrixTransform(matrix)
  
  		 return bbox
  		}
  
  		return tip
  		};