The correct way to modify TPaveText's NDC

[NgJunKai]

Let say I created a canvas, and I would like to modify the NDC of the title for the histogram.
the following code did not work and I got AttributeError: 'TObject' object has no attribute 'SetX1NDC'.
Using ROOT.gPad.Update() or Modified() also did not work.
please help

c = r.TCanvas("c","title",600,600)

histogram.Draw()

tpave = c.GetPrimitive('title')
tpave.SetX1NDC(0.3)
tpave.SetX2NDC(0.6)

c.Draw()

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ROOT Version: 6.26.00 (conda)
Platform: ubuntu20.04
Compiler: gcc9

---

[dastudillo]

Try

import ROOT as r
r.gStyle.SetTitleX(0.2)
r.gStyle.SetTitleY(0.99)
c = r.TCanvas("c","title",600,600)
#...

[NgJunKai]

It worked, but it is a ‘global’ way.
Do you know any ‘local’ way ?

[dastudillo]

I’m not sure there’s an option in NDC, but in any case I would remove the automatic titles with SetOptTitle(0) and draw my own titles at any position with TText or TLatex, which give more control anyway.

[NgJunKai]

OK, so it’s not as straightforward as what I think how it should be…
thanks.

[dastudillo]

You could do something like this too:

{
  TCanvas *c=new TCanvas();
  TH1F *h1 = new TH1F("h1", "histo from a gaussian", 100, -3, 3);
  h1->FillRandom("gaus", 500);
  h1->Draw();
  c->Modified();
  c->Update();
  TPaveText *pt = (TPaveText*)(c->GetPrimitive("title"));
  pt->SetX1NDC(0.1);
  pt->SetX2NDC(0.5);
  pt->SetY1NDC(0.8);
  pt->SetY2NDC(0.9);
  c->Modified();
  c->Update();
}