From 36b6acc3543595793d253f12a0e2c74df201d0f2 Mon Sep 17 00:00:00 2001
From: Albert Kong <akong25@gmail.com>
Date: Wed, 25 Feb 2026 09:32:38 +1030
Subject: [PATCH 1/3] [tree] Show truncation with ... in column name headers
 for Scan()

---
 tree/treeplayer/src/TTreePlayer.cxx | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tree/treeplayer/src/TTreePlayer.cxx b/tree/treeplayer/src/TTreePlayer.cxx
index 018be6645014c..512bc806063b9 100644
--- a/tree/treeplayer/src/TTreePlayer.cxx
+++ b/tree/treeplayer/src/TTreePlayer.cxx
@@ -2691,7 +2691,12 @@ Long64_t TTreePlayer::Scan(const char *varexp, const char *selection,
    if (hasArray) onerow += "* Instance ";
    for (ui=0;ui<ncols;ui++) {
       TString numbFormat = Form("* %%%d.%ds ",colSizes[ui],colSizes[ui]);
-      onerow += Form(numbFormat.Data(),var[ui]->PrintValue(-1));
+      TString varName = var[ui]->PrintValue(-1);
+      if (Int_t(varName.size()) > colSizes[ui]) {
+         varName.Resize(std::max(1, colSizes[ui] - 3));
+         varName += "...";
+      }
+      onerow += Form(numbFormat.Data(), varName.Data());
    }
    if (fScanRedirect)
       out<<onerow.Data()<<"*"<<std::endl;

From 02410bc4bbeee876a27ca8b4a110288629067920 Mon Sep 17 00:00:00 2001
From: Albert Kong <akong25@gmail.com>
Date: Thu, 26 Feb 2026 10:46:16 +1030
Subject: [PATCH 2/3] [tree] Dynamically resize column widths to fit names for
 Scan()

---
 tree/treeplayer/src/TTreePlayer.cxx | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tree/treeplayer/src/TTreePlayer.cxx b/tree/treeplayer/src/TTreePlayer.cxx
index 512bc806063b9..88a60c36989cb 100644
--- a/tree/treeplayer/src/TTreePlayer.cxx
+++ b/tree/treeplayer/src/TTreePlayer.cxx
@@ -2456,6 +2456,7 @@ Long64_t TTreePlayer::Scan(const char *varexp, const char *selection,
    UInt_t ui;
    UInt_t lenmax = 0;
    UInt_t colDefaultSize = 9;
+   UInt_t colMaxResizeWidth = 20;
    UInt_t colPrecision = 9;
    std::vector<TString> colFormats;
    std::vector<Int_t> colSizes;
@@ -2481,6 +2482,7 @@ Long64_t TTreePlayer::Scan(const char *varexp, const char *selection,
       opt.Remove(start,length("size")+numlen);
 
       colDefaultSize = atoi(num.Data());
+      colMaxResizeWidth = colDefaultSize;
       colPrecision = colDefaultSize;
       if (colPrecision>18) colPrecision = 18;
    }
@@ -2632,9 +2634,10 @@ Long64_t TTreePlayer::Scan(const char *varexp, const char *selection,
    }
    var = new TTreeFormula* [ncols];
 
-   for(ui=colFormats.size();ui<ncols;++ui) {
+   for (ui = colFormats.size(); ui < ncols; ++ui) {
       colFormats.push_back(defFormat);
-      colSizes.push_back(colDefaultSize);
+      UInt_t nameWidth = cnames[ui].size();
+      colSizes.push_back(std::clamp(nameWidth, colDefaultSize, colMaxResizeWidth));
    }
 
 //*-*- Create the TreeFormula objects corresponding to each column

From 503875629e11b4b531a64674f26a5f49d22085ab Mon Sep 17 00:00:00 2001
From: Albert Kong <akong25@gmail.com>
Date: Fri, 27 Feb 2026 09:53:43 +1030
Subject: [PATCH 3/3] [tree] Comment non-obvious column name truncation for
 Scan()

---
 tree/treeplayer/src/TTreePlayer.cxx | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tree/treeplayer/src/TTreePlayer.cxx b/tree/treeplayer/src/TTreePlayer.cxx
index 88a60c36989cb..3047d596d03d3 100644
--- a/tree/treeplayer/src/TTreePlayer.cxx
+++ b/tree/treeplayer/src/TTreePlayer.cxx
@@ -2699,6 +2699,7 @@ Long64_t TTreePlayer::Scan(const char *varexp, const char *selection,
          varName.Resize(std::max(1, colSizes[ui] - 3));
          varName += "...";
       }
+      // varName will be truncated further if necessary here (ie if colSizes[ui]<=3)
       onerow += Form(numbFormat.Data(), varName.Data());
    }
    if (fScanRedirect)