How do you make an SVG element mouse event bubble up through another element?

Question

I have a D3 line chart where I'm placing a rect 'behind' the chart. This rect has a mouse event attached to it, but the problem is my chart also has another rect overlaid 'above' the chart that also has events attached to it.

How do I get the lower rect mouse events to bubble up above the higher rect that is overlayed on top? Thanks so much!

I've created a Fiddle here:

http://jsfiddle.net/TnjCC/1/

And here is my code. Look for the "This is where I need the mouseover to bubble up" comment to see which element I'd like to bubble up.

var data = [
  {"date":"1-May-13","close":58.13},
  {"date":"30-Apr-13","close":53.98},
  {"date":"27-Apr-13","close":67.00},
  {"date":"26-Apr-13","close":89.70},
  {"date":"25-Apr-13","close":99.00},
  {"date":"24-Apr-13","close":130.28},
  {"date":"23-Apr-13","close":166.70},
  {"date":"20-Apr-13","close":234.98},
  {"date":"19-Apr-13","close":345.44},
  {"date":"18-Apr-13","close":443.34},
];

var margin = {top: 20, right: 50, bottom: 30, left: 50},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var parseDate = d3.time.format("%d-%b-%y").parse,
    bisectDate = d3.bisector(function(d) { return d.date; }).left,
    formatValue = d3.format(",.2f"),
    formatCurrency = function(d) { return "$" + formatValue(d); };

var x = d3.time.scale()
    .range([0, width]);

var y = d3.scale.linear()
    .range([height, 0]);

var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom");

var yAxis = d3.svg.axis()
    .scale(y)
    .orient("left");

var line = d3.svg.line()
    .x(function(d) { return x(d.date); })
    .y(function(d) { return y(d.close); });

var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

  data.forEach(function(d) {
    d.date = parseDate(d.date);
    d.close = +d.close;

  data.sort(function(a, b) {
    return a.date - b.date;
  });

  x.domain([data[0].date, data[data.length - 1].date]);
  y.domain(d3.extent(data, function(d) { return d.close; }));

  svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);

  svg.append("g")
      .attr("class", "y axis")
      .call(yAxis)
    .append("text")
      .attr("transform", "rotate(-90)")
      .attr("y", 6)
      .attr("dy", ".71em")
      .style("text-anchor", "end")
      .text("Price ($)");

  <!-- This is where I need the mouseover to bubble up -->
  var left = x(new Date("Apr 23 2013"));
  var right = x(new Date("Apr 26 2013"));
  var wid = right - left;
  svg.append("rect")
      .attr("id", "range")
      .attr("class", "range")
      .attr("x", left)
      .attr("width", wid)
      .attr("height", height)
      .on("mouseover", function () {
          alert("I can see you!");
      })      

  svg.append("path")
      .datum(data)
      .attr("class", "line")
      .attr("d", line);

  var focus = svg.append("g")
      .attr("class", "focus")
      .style("display", "none");

  focus.append("circle")
      .attr("r", 4.5);

  focus.append("text")
      .attr("x", 9)
      .attr("dy", ".35em");

  svg.append("rect")
      .attr("class", "overlay")
      .attr("width", width)
      .attr("height", height)
      .on("mouseover", function() { focus.style("display", null); })
      .on("mouseout", function() { focus.style("display", "none"); })
      .on("mousemove", mousemove);

  function mousemove() {
    var x0 = x.invert(d3.mouse(this)[0]),
        i = bisectDate(data, x0, 1),
        d0 = data[i - 1],
        d1 = data[i],
        d = x0 - d0.date > d1.date - x0 ? d1 : d0;
    focus.attr("transform", "translate(" + x(d.date) + "," + y(d.close) + ")");
    focus.select("text").text(formatCurrency(d.close));
  }
});

Answer 1

For a quick fix, you can move the range above the overlay and manually call the overlay event handlers from the range.

http://jsfiddle.net/Rk5Hp/

 svg.append("rect")
      .attr("class", "overlay")
      .attr("width", width)
      .attr("height", height)
      .on("mouseover", function() { focus.style("display", null); })
      .on("mouseout", function() { focus.style("display", "none"); })
      .on("mousemove", mousemove);

  // move range above overlay and call the overlay event handlers from there
  svg.append("rect")
      .attr("id", "range")
      .attr("class", "range")
      .attr("x", left)
      .attr("width", wid)
      .attr("height", height)
      .on("mousemove", mousemove)
      .on("mouseout", function() { focus.style("display", "none"); })
      .on("mouseover", function() {
          focus.style("display", null);
          // event handling for range mouseover (alert broke mouse move)
          console.log("I can see you!");
      });

Bubbling acts at the dom level, and since there is no way to have a rect be a child of another rect, bubbling will not take care of this for you. Grouping the elements together and placing a handler that checks the event target on the group will keep you from registering the event handler twice, but suffers from the same basic problem: when elements overlap, whichever element is declared last in the source order will get the event.

Answer 2

You can also use the following style, to "hide" certain svg elements for mouse events. In my case, it was the mouseover event, that I wanted to bubble through:

pointer-events: none;