How to avoid overlapping tooltips of multi-series line chart d3.js

Question

I' ve created tooltips on multi-series line chart following the answer here. If I mouse over the last date as you can see in this picture:

the tooltips are overlapping. What I want is when tooltips are overlapping, move any of them a little higher or lower. I was trying to do this by changing the code below.

   var beginning = 0,
        end = lines[i].getTotalLength(),
        target = null;
    //console.log(lines[i])             
    //console.log(end)
    while (true){
      target = Math.floor((beginning + end) / 2);
      pos = lines[i].getPointAtLength(target);
      if ((target === end || target === beginning) && pos.x !== mouse[0]) {
          break;
      }
      console.log(pos)
      if (pos.x > mouse[0])      end = target;
      else if (pos.x < mouse[0]) beginning = target;
      else break; //position found
    } 

My thought was recalculating the end. If the substraction of lines[0].getTotalLength() and lines[1].getTotalLength() is less than or larger than a value, then update the value of end(eg. end = end + 20).But I didn't get the code work here.

Does anybody know how to do this? Or is there an easier way to avoid tooltips overlapping?

Answer 1

See changes here:

https://jsfiddle.net/fk6gfwjr/1/

Basically the tooltips need to be sorted by y position, and then we make sure neighbouring tooltips in that sort order are separated by a minimum distance (i picked 15px). The offset to the previously calculated y position is then added to the tooltip text. I also coloured the text to make them easier to tell which is which.

    var ypos = [];

    d3.selectAll(".mouse-per-line")
      .attr("transform", function(d, i) {
        // same code as before
        // ...
          // add position to an array
          ypos.push ({ind: i, y: pos.y, off: 0});

        return "translate(" + mouse[0] + "," + pos.y +")";
      })
      // sort this array by y positions, and make sure each is at least 15 pixels separated
      // from the last, calculate an offset from their current y value,
      // then resort by index
      .call(function(sel) {
        ypos.sort (function(a,b) { return a.y - b.y; });
        ypos.forEach (function(p,i) {
            if (i > 0) {
            var last = ypos[i-1].y;
           ypos[i].off = Math.max (0, (last + 15) - ypos[i].y);
            ypos[i].y += ypos[i].off;
          }
        })
        ypos.sort (function(a,b) { return a.ind - b.ind; });
      })
      // Use the offset to move the tip text from it's g element
      // don't want to move the circle too
      .select("text")
        .attr("transform", function(d,i) {
            return "translate (10,"+(3+ypos[i].off)+")";
        }
      ;