Execution in wrong order

[FelixPetersen]

Hello,
I used the following code from the ROOTPrimer.pdf introduction in the interactive interpreter. [http://root.cern.ch/root/htmldoc/guides/primer/ROOTPrimer.pdf]

TH2F bidi_h("bidi_h","2D Histo;Gaussian Vals;Exp. Vals",
30,-5,5, // X axis
30,0,10); // Y axis

TRandom3 rgen;

for (int i=0;i<500000;i++) {bidi_h.Fill(rgen.Gaus(0,2),10-rgen.Exp(4),.1);}

auto c=new TCanvas("Canvas","Canvas",800,800);
c->Divide(2,2);
c->cd(1);bidi_h.DrawClone("Cont1");

The output of this is not as expected.
The “bidi_h.DrawClone(“Cont1”);” seems to be executed before the “c->Divide(2,2);” although the Divide is entered one line before. Alternatively it is possible that “c->cd(1);” could be executed after “bidi_h.DrawClone(“Cont1”);”.

This strange behavior doesn’t occur if I use:

c->cd(1);
bidi_h.DrawClone(“Cont1”);

instead of:

c->cd(1);bidi_h.DrawClone(“Cont1”);

This strange behavior also doesn’t occur if I use “Draw” instead of “DrawClone”.

Why does ROOT behave this way? Why seems the line before being executed after the next line?

[bellenot]

Hi,

Which ROOT version? which platform? which compiler?

Cheers, Bertrand.

[bellenot]

OK, I can reproduce the issue. Our graphics expert, @couet, will take care of it once he gets back. For the time being, just keep it on two lines:

c->cd(1);
bidi_h.DrawClone(“Cont1”);

Cheers, Bertrand.

[FelixPetersen]

ROOT 6.10/02
Built for macosx64

using the interactive interpreter

[couet]

Actually I see it even with the commands on 2 lines. I will check. Using Draw instead is fine …

[couet]

In the Cocoa case the Selected Pad behaves is set whereas it is not in the X11 one. If you really need to use DrawClone a workaround would be:

{
   auto h2 = new TH2F("h2","2D Histo;Gaussian Vals;Exp. Vals", 30,-5,5, 30,0,10);
   TRandom3 rgen;
   for (int i=0;i<500000;i++) h2->Fill(rgen.Gaus(0,2),10-rgen.Exp(4),.1);
   auto c=new TCanvas("Canvas","Canvas",800,800);
   c->Divide(2,2);
   gROOT->SetSelectedPad(c->cd(1));
   h2->DrawClone("Cont1");
}

That’s not satisfactory but I found no obvious (not having side effects) fix until now.