Can't see ProjectionYs of TH2F after Drawn on TCanvas. Bug or Feature?

[sstiefel19]

Dear experts,
I’m having a problem with projections of a TH2. On the TCanvas shown by root I only see blank spaces (see attachments). In the .root file in a TBrowser they are there as they should be. Is this a bug or am I doing sth wrong?
Thanks a lot in advance!

#include "TH1F.h"
#include "TH2F.h"
#include "TCanvas.h"
#include "TFile.h"

void testDraw(){
    
    TH2* h2 = new TH2F("t","t",2, 0., 1., 2, 0., 2);
    h2->Fill(.1, .1);
    
    TFile outfile("resolutions.root", "recreate");
    h2->Write();
    
    TCanvas *cR = new TCanvas("cR", "cR", 2000, 1000);
    cR->Divide(2,1);
    for (int i=1; i<=2; ++i){
        TH1* h1 = h2->ProjectionY(Form("h1_%d", i), i, i);
        h1->SetTitle(h1->GetName());
        h1->Write();
        cR->cd(i);
        h1->Draw();
    }
    TCanvas *c2 = new TCanvas("c2", "c2", 2000, 1000);
    h2->Draw("colz");
}
outfile.Close();

ROOT Version: 6.28/04
Platform: macosx64 (13.6.4)
Compiler: Homebrew clang version 15.0.7

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[Danilo]

Hi,

Thanks for your post.
It’s an ownership matter. By closing the file, you are removing the objects which are drawn.

I hope this helps.

Cheers,
Danilo

[sstiefel19]

Hi Danilo,
thanks, it helped. Not closing alone doesnt help (because outfile lives on the stack) but creating outfile on the heap and not closing it indeed solved the problem. Thanks!

[Danilo]

Glad to hear you are unblocked!