Transition hacking

A somewhat crazy method for turning an asynchronous d3 transition into something that can be paused/fast-forwarded/rewound while still using the nice syntax, easing, interpolation, etc. of d3.transition.

After a transition is declared with normal syntax, calling .record() on a selection inspects each element in a selection for the internals of its most recent transition. It generates an array of tweeners based on the transitions' tweens, the easing, and the elements' data. It then returns a wrapper function that will loop through and apply all of those tweeners for any arbitrary time value t (between 0 and 1).

This operates on the entire set of elements in the transition, but you could make it per-element with some changes.

This version only records the most recent transition and ignores delays. For a version that respects delays and chained transitions, see this example.

forked from veltman's block: Transition hacking

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

body {
    text-align: center;
    font: 16px sans-serif;
  }

button {
    margin: 0 0.5em;
  }

circle {
    stroke: none;
    fill: #de1e3d;
    opacity: 0.8;
  }

</style>
<body>
<script src="//cdnjs.cloudflare.com/ajax/libs/d3/3.5.14/d3.min.js"></script>
<script src="d3-record.js"></script>
<script>

var width = 760,
    height = 200,
    margin = 100;

var svg = d3.select("body").append("svg")
  .attr("width",width + margin * 2)
  .attr("height",height + margin * 2)
  .append("g")
    .attr("transform","translate(" + margin + " " + margin + ")")

var dots = svg.selectAll("circle")
  .data(d3.range(2))
  .enter()
  .append("circle")
    .attr("r",50)
    .attr("cx",function(d){
      return d ? width : 0;
    })
    .attr("cy",height / 2);

// Declare a normal transition
dots.transition()
  .duration(3000)
  .style("fill",function(d){
    return d ? "#0e88ba" : "#fc0";
  })
  .attr("cx",function(d){
    return d ? 0 : width;
  })
  .attr("r",function(d){
    return d ? 100 : 25;
  });

// "Record" the transition into a function that can jump to any time
var jumpToTime = dots.record();

d3.select("body").append("div")
  .text("Jump to: ")
  .selectAll("button")
  .data(d3.range(0,1.1,0.1))
  .enter()
  .append("button")
    .text(function(d){
      return (d * 100) + "%";
    })
    .on("click",jumpToTime);

</script>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.14/d3.min.js