Function getBackgroundPoint

src/plugins/plugin.tooltip.js:304–329

* Helper to get the location a tooltip needs to be placed at given the initial position (via the vm) and the size and alignment

(options, size, alignment, chart)

 * Helper to get the location a tooltip needs to be placed at given the initial position (via the vm) and the size and alignment
 */
function getBackgroundPoint(options, size, alignment, chart) {
  const {caretSize, caretPadding, cornerRadius} = options;
  const {xAlign, yAlign} = alignment;
  const paddingAndSize = caretSize + caretPadding;
  const {topLeft, topRight, bottomLeft, bottomRight} = toTRBLCorners(cornerRadius);

  let x = alignX(size, xAlign);
  const y = alignY(size, yAlign, paddingAndSize);

  if (yAlign === 'center') {
    if (xAlign === 'left') {
      x += paddingAndSize;
    } else if (xAlign === 'right') {
      x -= paddingAndSize;
    }
  } else if (xAlign === 'left') {
    x -= Math.max(topLeft, bottomLeft) + caretSize;
  } else if (xAlign === 'right') {
    x += Math.max(topRight, bottomRight) + caretSize;
  }

  return {
    x: _limitValue(x, 0, chart.width - size.width),
    y: _limitValue(y, 0, chart.height - size.height)
  };
}

function getAlignedX(tooltip, align, options) {
  const padding = toPadding(options.padding);