svg circles drawn for points maintain scale on zoom

README.md

This example shows the points, which represent coffee shops near my apartment, maintaining their scale as one zooms in and out. There are also tooltips on mouseover, using d3.tip.

coffee.csv

d3.tip.js

// d3.tip
// Copyright (c) 2013 Justin Palmer
//
// Tooltips for d3.js SVG visualizations

(function (root, factory) {
  if (typeof define === 'function' && define.amd) {
    // AMD. Register as an anonymous module with d3 as a dependency.
    define(['d3'], factory)
  } else if (typeof module === 'object' && module.exports) {
    // CommonJS
    module.exports = function(d3) {
      d3.tip = factory(d3)
      return d3.tip
    }
  } else {
    // Browser global.
    root.d3.tip = factory(root.d3)
  }
}(this, function (d3) {

  // Public - contructs a new tooltip
  //
  // Returns a tip
  return 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       = directions.length,
          coords,
          scrollTop  = document.documentElement.scrollTop || document.body.scrollTop,
          scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft

      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]) + scrollTop + 'px',
        left: (coords.left + poffset[1]) + scrollLeft + 'px'
      })

      return tip
    }

    // Public - hide the tooltip
    //
    // Returns a tip
    tip.hide = function() {
      var 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',
        top: 0,
        opacity: 0,
        'pointer-events': 'none',
        'box-sizing': '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;

      while ('undefined' === typeof targetel.getScreenCTM && 'undefined' === targetel.parentNode) {
          targetel = targetel.parentNode;
      }

      var bbox       = {},
          matrix     = targetel.getScreenCTM(),
          tbbox      = targetel.getBBox(),
          width      = tbbox.width,
          height     = tbbox.height,
          x          = tbbox.x,
          y          = tbbox.y

      point.x = x
      point.y = y
      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
  };

}));

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<style>

body {
  margin: 0;
}

#container {
  position: relative;
  overflow: hidden;
	background: #ddd;
}

#map{
	width:100%;
	height:100%;
}

#points{
	width:100%;
	height:100%;
	position:relative;
	z-index:100;
}

.layer {
  position: absolute;
}

.tile {
  pointer-events: none;
  position: absolute;
  width: 256px;
  height: 256px;
}

.coffee{
	opacity: 0.8;
	fill: #ff2200;
}

.coffee:hover{
	opacity: 1.0;
	fill: #ff8a00;
}

.d3-tip {
  line-height: 1.5;
  font-weight: normal;
	font-family: Helvetica, Arial, sans-serif;
	font-size:13px;
  padding: 10px;
  background: rgba(0, 0, 0, 0.8);
  color: #fff;
  border-radius: 3px;
	position:relative;
	z-index:101;
}

/* Creates a small triangle extender for the tooltip */
.d3-tip:after {
  box-sizing: border-box;
  display: inline;
  font-size: 20px;
  width: 100%;
  line-height: .5;
  color: rgba(0, 0, 0, 0.8);
  content: "\25BC";
  position: absolute;
  text-align: center;
}

/* Style northward tooltips differently */
.d3-tip.n:after {
  margin: -1px 0 0 0;
  top: 100%;
  left: 0;
}
</style>
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script src="http://d3js.org/d3.geo.tile.v0.min.js"></script>
<script src="d3.tip.js"></script>

<script>

var width = Math.max(960, window.innerWidth),
    height = Math.max(500, window.innerHeight),
    prefix = prefixMatch(["webkit", "ms", "Moz", "O"]);

	  d3.csv("coffee.csv", function(error, dataset) { createMap(dataset) });

var tile = d3.geo.tile()
    .size([width, height]);

var projection = d3.geo.mercator()
.scale((1 << 23) / 2 / Math.PI)
.translate([-width / 2, -height / 2]); // just temporary

var tileProjection = d3.geo.mercator();

var tilePath = d3.geo.path()
    .projection(tileProjection);

var zoom = d3.behavior.zoom()
    .scale(projection.scale() * 2 * Math.PI)
    .scaleExtent([1 << 9, 1 << 25])
    .translate(projection([-73.978277, 40.6791989]).map(function(x) { return -x; }))
    .on("zoom", zoomed);
		
var container = d3.select("body").append("div")
    .attr("id", "container")
    .style("width", width + "px")
    .style("height", height + "px")
    .call(zoom);

var map = container.append("g")
		.attr("id", "map")

var points = container.append("svg")
		.attr("id", "points")
				
var layer = map.append("div")
    .attr("class", "layer");

var tip = d3.tip()
	  .attr('class', 'd3-tip')
	  .offset([-10, 0])
	  .html(function(d) { return "<img src='img/" + d.img + "' class='treeimg'>" + d.num + ". " + d.name + "<br/>(" + d.genus + " " + d.species + ")"; })

var tip = d3.tip()
  	.attr('class', 'd3-tip')
		.offset([-10, 0])
		.html(function(d) { return d.name; })

points.call(tip);

zoomed();

function createMap(dataset) {
	d3.select("#points").selectAll("circle").data(dataset) //plotted 	locations on map
	.enter()
	.append("circle")
	.attr("cx", function(d) {return projection([d.y,d.x])[0]})
	.attr("cy", function(d) {return projection([d.y,d.x])[1]})
	.attr("class", "coffee")
	.on('mouseover', tip.show)
	.on('mouseout', tip.hide)	
	zoomed();
}

function zoomed() {
  var tiles = tile
      .scale(zoom.scale())
      .translate(zoom.translate())
      ();

  projection
      .scale(zoom.scale() / 2 / Math.PI)
      .translate(zoom.translate());

var circles = d3.selectAll("circle")
							.attr("cx", function(d) {return projection([d.y,d.x])[0]})
							.attr("cy", function(d) {return projection([d.y,d.x])[1]})
    					.attr("r", .0000012*zoom.scale());
			
  var image = layer
      .style(prefix + "transform", matrix3d(tiles.scale, tiles.translate))
    .selectAll(".tile")
      .data(tiles, function(d) { return d; });

  image.exit()
      .remove();

  image.enter().append("img")
      .attr("class", "tile")
			.attr("src", function(d) { return "http://" + ["a", "b", "c"][Math.random() * 3 | 0] + ".tile.openstreetmap.se/hydda/full/" + d[2] + "/" + d[0] + "/" + d[1] + ".png"; })
      .style("left", function(d) { return (d[0] << 8) + "px"; })
      .style("top", function(d) { return (d[1] << 8) + "px"; });
}

function matrix3d(scale, translate) {
  var k = scale / 256, r = scale % 1 ? Number : Math.round;
  return "matrix3d(" + [k, 0, 0, 0, 0, k, 0, 0, 0, 0, k, 0, r(translate[0] * scale), r(translate[1] * scale), 0, 1 ] + ")";
}

function prefixMatch(p) {
  var i = -1, n = p.length, s = document.body.style;
  while (++i < n) if (p[i] + "Transform" in s) return "-" + p[i].toLowerCase() + "-";
  return "";
}

function formatLocation(p, k) {
  var format = d3.format("." + Math.floor(Math.log(k) / 2 - 2) + "f");
  return (p[1] < 0 ? format(-p[1]) + "°S" : format(p[1]) + "°N") + " "
       + (p[0] < 0 ? format(-p[0]) + "°W" : format(p[0]) + "°E");
}

</script>
</body>
</html>

thumbnail.png