chartjs/chartjs-plugin-datalabels

import {isNullOrUndef} from 'chart.js/helpers';

var devicePixelRatio = (function() {
  if (typeof window !== 'undefined') {
    if (window.devicePixelRatio) {
      return window.devicePixelRatio;
    }

    // devicePixelRatio is undefined on IE10
    // https://stackoverflow.com/a/20204180/8837887
    // https://github.com/chartjs/chartjs-plugin-datalabels/issues/85
    var screen = window.screen;
    if (screen) {
      return (screen.deviceXDPI || 1) / (screen.logicalXDPI || 1);
    }
  }

  return 1;
}());

var utils = {
  // @todo move this in Chart.helpers.toTextLines
  toTextLines: function(inputs) {
    var lines = [];
    var input;

    inputs = [].concat(inputs);
    while (inputs.length) {
      input = inputs.pop();
      if (typeof input === 'string') {
        lines.unshift.apply(lines, input.split('\n'));
      } else if (Array.isArray(input)) {
        inputs.push.apply(inputs, input);
      } else if (!isNullOrUndef(inputs)) {
        lines.unshift('' + input);
      }
    }

    return lines;
  },

  // @todo move this in Chart.helpers.canvas.textSize
  // @todo cache calls of measureText if font doesn't change?!
  textSize: function(ctx, lines, font) {
    var items = [].concat(lines);
    var ilen = items.length;
    var prev = ctx.font;
    var width = 0;
    var i;

    ctx.font = font.string;

    for (i = 0; i < ilen; ++i) {
      width = Math.max(ctx.measureText(items[i]).width, width);
    }

    ctx.font = prev;

    return {
      height: ilen * font.lineHeight,
      width: width
    };
  },

  /**
   * Returns value bounded by min and max. This is equivalent to max(min, min(value, max)).
   * @todo move this method in Chart.helpers.bound
   * https://doc.qt.io/qt-5/qtglobal.html#qBound
   */
  bound: function(min, value, max) {
    return Math.max(min, Math.min(value, max));
  },

  /**
   * Returns an array of pair [value, state] where state is:
   * * -1: value is only in a0 (removed)
   * *  1: value is only in a1 (added)
   */
  arrayDiff: function(a0, a1) {
    var prev = a0.slice();
    var updates = [];
    var i, j, ilen, v;

    for (i = 0, ilen = a1.length; i < ilen; ++i) {
      v = a1[i];
      j = prev.indexOf(v);

      if (j === -1) {
        updates.push([v, 1]);
      } else {
        prev.splice(j, 1);
      }
    }

    for (i = 0, ilen = prev.length; i < ilen; ++i) {
      updates.push([prev[i], -1]);
    }

    return updates;
  },

  /**
   * https://github.com/chartjs/chartjs-plugin-datalabels/issues/70
   */
  rasterize: function(v) {
    return Math.round(v * devicePixelRatio) / devicePixelRatio;
  }
};

export default utils;