Using Texec to show a TH1F from a TCanvas pad on another TCanvas


I would like to make use of TExec (or AddExec()) to show a histogram (TH1F) plotted on a single pad of a TCanvas divided into several pads on another (larger) TCanvas for easier inspection.

What I tried so far is the following code:

TCanvas *c2 = 0;

void show()
  auto event = gPad->GetEvent();  
  if (event != 11)  return; 

  TObject *select = gPad->GetSelected();
  if (!select) return;
  if (!select->InheritsFrom(TH1::Class())) return;

  TH1F *h = (TH1F*)select; 

void testexec()
  TCanvas *c1 = new TCanvas("c1","c1",10,10,800,600);

  c2 = new TCanvas("c2","c2",900,20,500,500);
  TH1F *h[12];
  for (int i=0; i<12; ++i) {
    h[i] = new TH1F(Form("h%d",i), Form("h%d",i), 100,0,1);
    for (int j=0; j<10000; ++j) h[i]->Fill(gRandom->Gaus(0.1+0.05*i,0.01*i+0.05));

This doesn’t do anything, i.e. nothing happens when clicking on the histograms. If I comment out the ‘InheritsFrom’ line, strange stuff is drawn on c2, and the histograms on c1 vanish.

Could somebody help me with that?

Best regards and thanks,

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ROOT Version: 6.22/06
Platform: Not Provided
Compiler: Not Provided

Do you “click on the histograms” when the “mouse pointer” is changed into an “arrow tip” (i.e., not a “cross”)?

BTW. Use: h->DrawCopy();

Thanks for the hint.

When I use DrawCopy and click with the arrow tip (i.e. I’m exactly on the histogram line), it works. How could I get it working when the pointer is a cross? Is this the pad itself, from which I could retrieve the histogram?

You would need to “scan” the list returned by: gPad->GetListOfPrimitives()

That works, thanks! In case somebody is interested here the code:

void show()
  if (gPad->GetEvent() != 11)  return; 
  TH1 *h = 0;
  // histogram was clicked
  TObject *select = gPad->GetSelected();
  if (!select) return;
  if (select->InheritsFrom(TH1::Class())) h = (TH1F*)select;
  // pad was clicked
  if (h==0) {  
    TIter next(gPad->GetListOfPrimitives());
    while (TObject *obj = next()) 
      if (obj->InheritsFrom(TH1::Class())) h = (TH1F*) obj;

  if (h!=0) {

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