From 79a5dc5b1105dc589bfed80170416187c0d0ea08 Mon Sep 17 00:00:00 2001
From: Felix Schlepper <felix.schlepper@cern.ch>
Date: Mon, 16 Jun 2025 15:38:57 +0200
Subject: [PATCH] ITS: fix clusterSize propagation

After recent refactoring, this started to push to the end of the vector, which was preallocated.
@ddobrigk this should fix the cluster size in ao2d.
---
 Detectors/ITSMFT/ITS/tracking/src/TimeFrame.cxx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Detectors/ITSMFT/ITS/tracking/src/TimeFrame.cxx b/Detectors/ITSMFT/ITS/tracking/src/TimeFrame.cxx
index dbb1631a4eb10..1a3132413c450 100644
--- a/Detectors/ITSMFT/ITS/tracking/src/TimeFrame.cxx
+++ b/Detectors/ITSMFT/ITS/tracking/src/TimeFrame.cxx
@@ -180,7 +180,7 @@ int TimeFrame<nLayers>::loadROFrameData(gsl::span<o2::itsmft::ROFRecord> rofs,
         locXYZ = dict->getClusterCoordinates(c, patt, false);
         clusterSize = patt.getNPixels();
       }
-      mClusterSize.push_back(std::clamp(clusterSize, 0u, 255u));
+      mClusterSize[clusterId] = std::clamp(clusterSize, 0u, 255u);
       auto sensorID = c.getSensorID();
       // Inverse transformation to the local --> tracking
       auto trkXYZ = geom->getMatrixT2L(sensorID) ^ locXYZ;