en/builder/src/echarts3/chart/graph/edgeVisual.js

function normalize(a) {
  if (!(a instanceof Array)) {
    a = [a, a];
  }

  return a;
}

export default function (ecModel) {
  ecModel.eachSeriesByType('graph', function (seriesModel) {
    var graph = seriesModel.getGraph();
    var edgeData = seriesModel.getEdgeData();
    var symbolType = normalize(seriesModel.get('edgeSymbol'));
    var symbolSize = normalize(seriesModel.get('edgeSymbolSize'));
    var colorQuery = 'lineStyle.normal.color'.split('.');
    var opacityQuery = 'lineStyle.normal.opacity'.split('.');
    edgeData.setVisual('fromSymbol', symbolType && symbolType[0]);
    edgeData.setVisual('toSymbol', symbolType && symbolType[1]);
    edgeData.setVisual('fromSymbolSize', symbolSize && symbolSize[0]);
    edgeData.setVisual('toSymbolSize', symbolSize && symbolSize[1]);
    edgeData.setVisual('color', seriesModel.get(colorQuery));
    edgeData.setVisual('opacity', seriesModel.get(opacityQuery));
    edgeData.each(function (idx) {
      var itemModel = edgeData.getItemModel(idx);
      var edge = graph.getEdgeByIndex(idx);
      var symbolType = normalize(itemModel.getShallow('symbol', true));
      var symbolSize = normalize(itemModel.getShallow('symbolSize', true)); // Edge visual must after node visual

      var color = itemModel.get(colorQuery);
      var opacity = itemModel.get(opacityQuery);

      switch (color) {
        case 'source':
          color = edge.node1.getVisual('color');
          break;

        case 'target':
          color = edge.node2.getVisual('color');
          break;
      }

      symbolType[0] && edge.setVisual('fromSymbol', symbolType[0]);
      symbolType[1] && edge.setVisual('toSymbol', symbolType[1]);
      symbolSize[0] && edge.setVisual('fromSymbolSize', symbolSize[0]);
      symbolSize[1] && edge.setVisual('toSymbolSize', symbolSize[1]);
      edge.setVisual('color', color);
      edge.setVisual('opacity', opacity);
    });
  });
}