@dagrejs/dagre/lib/normalize.js

Graph layout for JavaScript

"use strict";

let util = require("./util");

module.exports = {
  run: run,
  undo: undo
};

/*
 * Breaks any long edges in the graph into short segments that span 1 layer
 * each. This operation is undoable with the denormalize function.
 *
 * Pre-conditions:
 *
 *    1. The input graph is a DAG.
 *    2. Each node in the graph has a "rank" property.
 *
 * Post-condition:
 *
 *    1. All edges in the graph have a length of 1.
 *    2. Dummy nodes are added where edges have been split into segments.
 *    3. The graph is augmented with a "dummyChains" attribute which contains
 *       the first dummy in each chain of dummy nodes produced.
 */
function run(g) {
  g.graph().dummyChains = [];
  g.edges().forEach(edge => normalizeEdge(g, edge));
}

function normalizeEdge(g, e) {
  let v = e.v;
  let vRank = g.node(v).rank;
  let w = e.w;
  let wRank = g.node(w).rank;
  let name = e.name;
  let edgeLabel = g.edge(e);
  let labelRank = edgeLabel.labelRank;

  if (wRank === vRank + 1) return;

  g.removeEdge(e);

  let dummy, attrs, i;
  for (i = 0, ++vRank; vRank < wRank; ++i, ++vRank) {
    edgeLabel.points = [];
    attrs = {
      width: 0, height: 0,
      edgeLabel: edgeLabel, edgeObj: e,
      rank: vRank
    };
    dummy = util.addDummyNode(g, "edge", attrs, "_d");
    if (vRank === labelRank) {
      attrs.width = edgeLabel.width;
      attrs.height = edgeLabel.height;
      attrs.dummy = "edge-label";
      attrs.labelpos = edgeLabel.labelpos;
    }
    g.setEdge(v, dummy, { weight: edgeLabel.weight }, name);
    if (i === 0) {
      g.graph().dummyChains.push(dummy);
    }
    v = dummy;
  }

  g.setEdge(v, w, { weight: edgeLabel.weight }, name);
}

function undo(g) {
  g.graph().dummyChains.forEach(v => {
    let node = g.node(v);
    let origLabel = node.edgeLabel;
    let w;
    g.setEdge(node.edgeObj, origLabel);
    while (node.dummy) {
      w = g.successors(v)[0];
      g.removeNode(v);
      origLabel.points.push({ x: node.x, y: node.y });
      if (node.dummy === "edge-label") {
        origLabel.x = node.x;
        origLabel.y = node.y;
        origLabel.width = node.width;
        origLabel.height = node.height;
      }
      v = w;
      node = g.node(v);
    }
  });
}