text: var vec2 = require("zrender/lib/core/vector");
  
  function circularLayout(seriesModel) {
    var coordSys = seriesModel.coordinateSystem;
  
    if (coordSys && coordSys.type !== 'view') {
      return;
    }
  
    var rect = coordSys.getBoundingRect();
    var nodeData = seriesModel.getData();
    var graph = nodeData.graph;
    var angle = 0;
    var sum = nodeData.getSum('value');
    var unitAngle = Math.PI * 2 / (sum || nodeData.count());
    var cx = rect.width / 2 + rect.x;
    var cy = rect.height / 2 + rect.y;
    var r = Math.min(rect.width, rect.height) / 2;
    graph.eachNode(function (node) {
      var value = node.getValue('value');
      angle += unitAngle * (sum ? value : 1) / 2;
      node.setLayout([r * Math.cos(angle) + cx, r * Math.sin(angle) + cy]);
      angle += unitAngle * (sum ? value : 1) / 2;
    });
    nodeData.setLayout({
      cx: cx,
      cy: cy
    });
    graph.eachEdge(function (edge) {
      var curveness = edge.getModel().get('lineStyle.curveness') || 0;
      var p1 = vec2.clone(edge.node1.getLayout());
      var p2 = vec2.clone(edge.node2.getLayout());
      var cp1;
      var x12 = (p1[0] + p2[0]) / 2;
      var y12 = (p1[1] + p2[1]) / 2;
  
      if (+curveness) {
        curveness *= 3;
        cp1 = [cx * curveness + x12 * (1 - curveness), cy * curveness + y12 * (1 - curveness)];
      }
  
      edge.setLayout([p1, p2, cp1]);
    });
  }
  
  exports.circularLayout = circularLayout;