From b343fcc24ea9f855d1c4085d0803e927bcfd5d6e Mon Sep 17 00:00:00 2001
From: meffmadd <37695050+meffmadd@users.noreply.github.com>
Date: Fri, 23 Apr 2021 15:47:43 +0200
Subject: [PATCH] Fix selection of histograms with multiple traces (#2771)

* sort indices only if a single trace exists
---
 packages/javascript/plotlywidget/src/Figure.js | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/packages/javascript/plotlywidget/src/Figure.js b/packages/javascript/plotlywidget/src/Figure.js
index a997ae7533..62b301a8ec 100644
--- a/packages/javascript/plotlywidget/src/Figure.js
+++ b/packages/javascript/plotlywidget/src/Figure.js
@@ -1,7 +1,7 @@
 var widgets = require("@jupyter-widgets/base");
 var _ = require("lodash");
 
-window.PlotlyConfig = { MathJaxConfig: "local" };
+window.PlotlyConfig = {MathJaxConfig: "local"};
 var Plotly = require("plotly.js/dist/plotly");
 var semver_range = "^" + require("../package.json").version;
 
@@ -919,9 +919,18 @@ var FigureView = widgets.DOMWidgetView.extend({
             pointsObject["trace_indexes"][flatPointIndex] = pointObjects[p]["curveNumber"];
           }
         }
-        pointsObject["point_indexes"].sort(function(a, b) {
-          return a - b;
-        });
+
+        let single_trace = true;
+        for (let i = 1; i < numPointNumbers; i++) {
+          single_trace = single_trace && (pointsObject["trace_indexes"][i - 1] === pointsObject["trace_indexes"][i])
+          if (!single_trace) break;
+        }
+        if (single_trace) {
+          pointsObject["point_indexes"].sort((function (a, b) {
+            return a - b
+          }))
+        }
+
       } else {
         for (var p = 0; p < numPoints; p++) {
           pointsObject["trace_indexes"][p] = pointObjects[p]["curveNumber"];