Function fitWithPointLabels

src/scales/scale.radialLinear.js:49–116

* Helper function to fit a radial linear scale with point labels

(scale)

 * Helper function to fit a radial linear scale with point labels
 */
function fitWithPointLabels(scale) {

  // Right, this is really confusing and there is a lot of maths going on here
  // The gist of the problem is here: https://gist.github.com/nnnick/696cc9c55f4b0beb8fe9
  //
  // Reaction: https://dl.dropboxusercontent.com/u/34601363/toomuchscience.gif
  //
  // Solution:
  //
  // We assume the radius of the polygon is half the size of the canvas at first
  // at each index we check if the text overlaps.
  //
  // Where it does, we store that angle and that index.
  //
  // After finding the largest index and angle we calculate how much we need to remove
  // from the shape radius to move the point inwards by that x.
  //
  // We average the left and right distances to get the maximum shape radius that can fit in the box
  // along with labels.
  //
  // Once we have that, we can find the centre point for the chart, by taking the x text protrusion
  // on each side, removing that from the size, halving it and adding the left x protrusion width.
  //
  // This will mean we have a shape fitted to the canvas, as large as it can be with the labels
  // and position it in the most space efficient manner
  //
  // https://dl.dropboxusercontent.com/u/34601363/yeahscience.gif

  // Get maximum radius of the polygon. Either half the height (minus the text width) or half the width.
  // Use this to calculate the offset + change. - Make sure L/R protrusion is at least 0 to stop issues with centre points
  const orig = {
    l: scale.left + scale._padding.left,
    r: scale.right - scale._padding.right,
    t: scale.top + scale._padding.top,
    b: scale.bottom - scale._padding.bottom
  };
  const limits = Object.assign({}, orig);
  const labelSizes = [];
  const padding = [];
  const valueCount = scale._pointLabels.length;
  const pointLabelOpts = scale.options.pointLabels;
  const additionalAngle = pointLabelOpts.centerPointLabels ? PI / valueCount : 0;

  for (let i = 0; i < valueCount; i++) {
    const opts = pointLabelOpts.setContext(scale.getPointLabelContext(i));
    padding[i] = opts.padding;
    const pointPosition = scale.getPointPosition(i, scale.drawingArea + padding[i], additionalAngle);
    const plFont = toFont(opts.font);
    const textSize = measureLabelSize(scale.ctx, plFont, scale._pointLabels[i]);
    labelSizes[i] = textSize;

    const angleRadians = _normalizeAngle(scale.getIndexAngle(i) + additionalAngle);
    const angle = Math.round(toDegrees(angleRadians));
    const hLimits = determineLimits(angle, pointPosition.x, textSize.w, 0, 180);
    const vLimits = determineLimits(angle, pointPosition.y, textSize.h, 90, 270);
    updateLimits(limits, orig, angleRadians, hLimits, vLimits);
  }