// Make svg pannable and zoomable.
// Call clickHandler(t) if a click event is caught by the pan event handlers.
function initPanAndZoom(svg, clickHandler) {
  'use strict';

  // Current mouse/touch handling mode
  const IDLE = 0;
  const MOUSEPAN = 1;
  const TOUCHPAN = 2;
  const TOUCHZOOM = 3;
  let mode = IDLE;

  // State needed to implement zooming.
  let currentScale = 1.0;
  const initWidth = svg.viewBox.baseVal.width;