08-27-周三_17-09-29

node_modules/dagre-layout/lib/order/init-order.js

@@ -0,0 +1,36 @@
+import _ from 'lodash'
+
+/*
+ * Assigns an initial order value for each node by performing a DFS search
+ * starting from nodes in the first rank. Nodes are assigned an order in their
+ * rank as they are first visited.
+ *
+ * This approach comes from Gansner, et al., "A Technique for Drawing Directed
+ * Graphs."
+ *
+ * Returns a layering matrix with an array per layer and each layer sorted by
+ * the order of its nodes.
+ */
+function initOrder (g) {
+  const visited = {}
+  const simpleNodes = _.filter(g.nodes(), function (v) {
+    return !g.children(v).length
+  })
+  const maxRank = _.max(_.map(simpleNodes, function (v) { return g.node(v).rank }))
+  const layers = _.map(_.range(maxRank + 1), function () { return [] })
+
+  function dfs (v) {
+    if (_.has(visited, v)) return
+    visited[v] = true
+    const node = g.node(v)
+    layers[node.rank].push(v)
+    _.forEach(g.successors(v), dfs)
+  }
+
+  const orderedVs = _.sortBy(simpleNodes, function (v) { return g.node(v).rank })
+  _.forEach(orderedVs, dfs)
+
+  return layers
+}
+
+export default initOrder