gPad is not consistent in pyROOT

[linev]

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Description

If configuring any web display, gPad is not properly set.
As a result, h.Draw creates new canvas.
Code works properly when gROOT.SetWebDisplay("off") invoked.

Reproducer

Here is reproducer:

import ROOT

ROOT.gROOT.SetWebDisplay("")

c = ROOT.TCanvas()

if ROOT.gPad:
   print("gPad name", ROOT.gPad.GetName(), "editable", ROOT.gPad.IsEditable())
else:
   print("gPad is not there - why?")

h = ROOT.TH1D("","",64, -4,4)
h.FillRandom("gaus")

# this is a problem - histogram do not "see" gPad and creates new canvas
h.Draw()

input("Press Enter to exit")

ROOT version

master branch

Python 3.11.9

Installation method

build from source

Operating system

OpenSUSE linux

Additional context

No response

[vepadulano]

Just to confirm, this only happens when running ROOT from Python right? An equivalent C++ code would work?

[linev]

Yes, similar C++ code works as expected:

{
   gROOT->SetWebDisplay("");

   auto c = new TCanvas();

   if (gPad)
      printf("gPad name %s editable %d\n", gPad->GetName(), gPad->IsEditable());
   else
      printf("gPad is not there - why?\n");

   auto h = new TH1D("","",64, -4,4);
   h->FillRandom("gaus");

   // this is a problem - histogram do not "see" gPad and creates new canvas
   h->Draw();
}

[linev]

I just not understand how gPad can differ in h.Draw.
Are there any special pythonization for it?
Or is there other thread? gPad is thread-local variable.

[dpiparo]

@couet we need perhaps help

[linev]

I do not think Olivier can help here.

Something wired with pythonization here.
At the moment when h.Draw() is called gPad is not consistent.