Trim long tooltip title in doughnut chart

[RomanticCat]

Hi all,

I had some problem with long tooltips in doughnut chart.
Which could be googled by following url

http://stackoverflow.com/questions/28476159/chart-js-pie-tooltip-getting-cut

Eventually, I solved this issue with following option code using callbacks.
Can we make this configuration as parameters? Currently chart.js support responsive
and seem to detect width of context.

It seems to be long issue, and will be great if chart.js can support this feature.

Cheers,

---

var chartOptions = {
  title: {
    text: titleText
  },
  legend: {
    display: true,
    labels: {
      fontSize: 10
    },
    position: 'bottom'
  },
  tooltips: {
    mode: 'single',
    callbacks: {
      label: function(tooltipItems, data) {

        var linebreakAt = 20;
        var value = data.datasets[0].data[tooltipItems.index];

        var label = data.labels[tooltipItems.index];
        label = value + ' - ' + label;

        var returnText = [];

        for (var lineIdx = 0; (lineIdx * linebreakAt) < label.length; lineIdx++) {
          var currentLoc = lineIdx * linebreakAt;
          var lineText;

          if ((currentLoc + linebreakAt) < label.length) {
            lineText = label.substring(currentLoc, currentLoc + linebreakAt);
          } else {
            lineText = label.substring(currentLoc, label.length);
          }
          if (lineIdx == 0) {
            returnText = [lineText];
          } else {
            returnText.push(lineText);
          }
        }
        return returnText;
      }
    }
  }
};

[etimberg]

@RomanticCat could you PR these changes?

[kurkle]

I'm not sure this should be implemented in core, because there are so many different use cases on how to wrap the text.
Maybe move to discussion, as a tip?