Printed SVG image contains newline cutting through XML tags

[ShamrockLee]

• Checked for duplicates

Describe the bug

When plotting to SVG file the way

hist->Draw();
gPad->Print("hist.svg");

The produced SVG file is occasionally broken due to the newline character being inserted to the middle of the closing XML tag.

The error might be caused by certain kind of 250-character-per-line limit.

Expected behavior

The newline should be inserted somewhere before the closing XML tag.

Please don't remove all the new lines just to workaround this bug. It is great to have readable SVG outputs.

To Reproduce

1. Prepare the reproduction code
   Reproduce.C

#include<TCanvas.h>
#include<TPad.h>
#include<TFile.h>
#include<TH1.h>

void Reproduce(const char *pathFileIn="hsimple.root") {
  TCanvas::MakeDefCanvas();
  TFile *tfIn = TFile::Open(pathFileIn);
  TH1* hpxLongTitle = static_cast<TH1*>(tfIn->Get<TH1>("hpx")->Clone("hpxLongTitle"));
  hpxLongTitle->SetTitle("SupercalifragilisticexpialidociousHonorificabilitudinitatibusFloccinaucinihilipilificationFreeSesquipedalianTitleOnTheSupercalifragilisticexpialidociousHonorificabilitudinitatibusFloccinaucinihilipilificationFreeHist");
  hpxLongTitle->Draw();
  gPad->Print("hpxLongTitle.svg");
  tfIn->Close();
}

int main(int argc, char* argv[]) {
  if ( argc > 1 ) {
    Reproduce(argv[1]);
  } else {
    Reproduce();
  }
}

2. Run by

$ root -l -q 'Reproduce.C++("path/to/hsimple.root")'

or by

$ g++ $(root-config --glibs --cflags) -o Reproduce.o Reproduce.C
$ ./Reproduce.o "path/to/hsimple.root"

3. See the generated hpxLongTitle.svg
4. Open with a text editor and scroll to the bottom (pressing G for vim)
5. See the broken XML tag

Setup

1. ROOT Version: 6.25/01, built for linuxx8664gcc on Jan 01 1980, 00:00:00
2. Operating System: NixOS
3. Build with Nix package manager from master, revision 7821ed1

Additional context

The actual content of that supercali-title in my use case is a JSON string without any space character.

The generated SVG file (add the .txt suffix to workaround GitHub's limitation):
hpxLongTitle.svg.txt

[ShamrockLee]

In

core/base/src/TVirtualPS.cxx

There goes

const Int_t kMaxBuffer = 250;

[dpiparo]

This is not an area where I would call myself an expert, by far. However, I have a naive observation: wouldn't the fix just consist in raising the limit of kMaxBuffer to something far higher than 250 and maybe add a check to that number to stop the svg production if the string is longer than that limit?

[couet]

Fix here: #14590

[ShamrockLee]

Cool!

[couet]

PR Merged