From f63710d69eb4719040cc90c98a50ed4c15b60583 Mon Sep 17 00:00:00 2001
From: katsuhisa yuasa <berupon@gmail.com>
Date: Sun, 15 Dec 2024 16:13:33 +0900
Subject: [PATCH] reduce crossings of connection lines

---
 source/dagre.js | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/source/dagre.js b/source/dagre.js
index c614360910..cf8c274037 100644
--- a/source/dagre.js
+++ b/source/dagre.js
@@ -1367,11 +1367,27 @@ dagre.layout = (nodes, edges, layout, state) => {
         const calcDir = (idx0, idx1) => (idx0 < idx1) ? 1 : 2;
         for (let i = 4; i < best.length; i += 2) {
             const layer = best[i];
+            const upperLayer = best[i - 1];
             for (let j = 0; j < layer.length; ++j) {
                 const node = g.nodes.get(layer[j]);
-                if (node.in && node.in.length === 2) {
-                    let n0 = node.in[0].vNode.in[0].vNode;
-                    let n1 = node.in[1].vNode.in[0].vNode;
+                if (!node.in || node.in.length < 2) {
+                    continue;
+                }
+                const i2s = [];
+                for (let i2 = 0; i2 < node.in.length - 2; ++i2) {
+                    i2s.push(i2);
+                }
+                for (let i2 = node.in.length - 2; i2 >= 0; --i2) {
+                    i2s.push(i2);
+                }
+                const inputIndexes = [];
+                for (let i2 = 0; i2 < node.in.length; ++i2) {
+                    inputIndexes.push(upperLayer.indexOf(node.in[i2].v));
+                }
+                inputIndexes.sort((a, b) => a - b);
+                for (const i2 of i2s) {
+                    let n0 = g.node(upperLayer[inputIndexes[i2 + 0]]).in[0].vNode;
+                    let n1 = g.node(upperLayer[inputIndexes[i2 + 1]]).in[0].vNode;
                     const indexes = [];
                     let dirTotal = 0;
                     for (let k = i - 2; k >= 0; k -= 2) {
@@ -1388,6 +1404,11 @@ dagre.layout = (nodes, edges, layout, state) => {
                             || n1.out.length !== 1
                         ) {
                             if (dirTotal === 3) {
+                                {
+                                    const idx1 = inputIndexes[i2 + 0];
+                                    const idx0 = inputIndexes[i2 + 1];
+                                    [upperLayer[idx0], upperLayer[idx1]] = [upperLayer[idx1], upperLayer[idx0]];
+                                }
                                 const topDir = dir;
                                 let l = k + 2;
                                 while (indexes.length !== 0) {