From 3172d44fb324a9c478d6f878c2b89cecc3a4ac88 Mon Sep 17 00:00:00 2001
From: milandomazet <125308248+milandomazet@users.noreply.github.com>
Date: Thu, 8 Aug 2024 15:52:37 +0200
Subject: [PATCH] Fix Merged track popup bug (#1869)

---
 js/feature/mergedTrack.js | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/js/feature/mergedTrack.js b/js/feature/mergedTrack.js
index a7f3e1a87..3eace8bc6 100644
--- a/js/feature/mergedTrack.js
+++ b/js/feature/mergedTrack.js
@@ -227,7 +227,14 @@ class MergedTrack extends TrackBase {
 
         const promises = this.tracks.map((t) => t.getFeatures(chr, bpStart, bpEnd, bpPerPixel))
         const featureArrays = await Promise.all(promises)
-        return new MergedFeatureCollection(featureArrays)
+        
+        if (featureArrays.every((arr) => arr.length === 0)){
+            return new MergedFeatureCollection([], [])
+        }
+        else {
+            const trackNames = this.tracks.map((t) => t.name)
+            return new MergedFeatureCollection(featureArrays, trackNames)
+        }
     }
 
     draw(options) {
@@ -446,8 +453,11 @@ class MergedTrack extends TrackBase {
 
 class MergedFeatureCollection {
 
-    constructor(featureArrays) {
+    constructor(featureArrays,trackNames) {
         this.featureArrays = featureArrays
+        //trackNames is needed for the popup data to populate track names 
+        //preserving the order of the actual tracks
+        this.trackNames = trackNames
     }
 
     getMax(start, end) {