Cache getScreenCTM on start?

[mbostock]

I wonder if it’s worth caching getScreenCTM (and getBoundingClientRect) on start, since they shouldn’t change during a drag gesture?

function pointSvg(node, point) {
  var matrix = node.getScreenCTM().inverse();
  return function(event) {
    point.x = event.clientX, point.y = event.clientY;
    point = point.matrixTransform(matrix);
    return [point.x, point.y];
  };
}

function pointHtml(node) {
  var rect = node.getBoundingClientRect(),
      left = rect.left + node.clientLeft,
      top = rect.top + node.clientTop;
  return function(event) {
    return [event.clientX - left, event.clientY - top];
  };
}

export default function(node) {
  var svg = node.ownerSVGElement || node;
  return svg.createSVGPoint ? pointSvg(node, svg.createSVGPoint()) : pointHtml(node);
}

Related d3/d3#1797.

[mbostock]

Not going to pursue this for now.