Transition "step" events.

[mbostock]

And possibly allowing "text" tweening.

[xaedes]

A simple text tweening implementation I use:

  var textTweenID = 0;
  transition.textTween = function(tween, precision) {

    /** @this {Element} */
    function textTween(d, i) {
      var f = tween.call(this, d, i, this.textContent);
      return function(t) {
        this.textContent = f(t);
      };
    }
    tweens["text." + textTweenID] = textTween;
    textTweenID++;
    return transition;
  };
  
  transition.text = function(value) {

    return transition.textTween(d3_transitionTween(value));
  };

Btw: I would love to see transition "step" events!

[mbostock]

Thanks for the suggestion. Text transitions will be in the next release! See commit @222629a7a774ce15f3c8 for details.

I haven't decided whether to add "step" events yet. I'm a bit worried about the overhead on dispatching every tick times every element, when in the common case there is no step event listener. If I can find a way around that, it should be a no-brainer to add.

[mbostock]

Fixed in 2.0.0, using custom tweens.

[tandu]

Should I write custom tween as in example above to fire step events?

[mbostock]

Something like this:

transition.tween("name", function(d, i) {
  return function(t) {
    // this function is called with the easing parameter t in [0,1]
  };
});

The name is used as an identifier so that you can replace the tween later. For example, attr("foo", "bar") uses the name "attr.foo".