[PyROOT, Graphics] Cannot pause pyROOT script with `input()` and see canvases

[dpiparo]

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Description

This script used to work, also on MacOS

import ROOT

h = ROOT.TH1F("foo", "bar", 64, -4, 4)
h.FillRandom("gaus")
c=ROOT.TCanvas()
h.Draw()
c.Update()

input()

and allowed to see and interact with the canvas to then end execution upon pressing a key. This results now in a deadlock in master.

Reproducer

import ROOT

h = ROOT.TH1F("foo", "bar", 64, -4, 4)
h.FillRandom("gaus")
c=ROOT.TCanvas()
h.Draw()
c.Update()

input()

ROOT version

master

Installation method

built from sources

Operating system

MacOS

Additional context

No response

[linev]

I can reproduce problem with input() also on my Linux,
And I see that MacOS handled differently.
I will provide PR soon to see if small changes could help

[dpiparo]

Reopened b/c of this #13754

[linev]

Seems to be it is not possible to run extra thread in python on Mac in script mode.
At the same time input hook is also not working in script mode.
Thus canvas - even shown - remains fully frozen.
It is exactly a situation as was in previous ROOT releases.

In web case this leads just to empty web browser.
Probably I can improve this

[Axel-Naumann]

Do I understand correctly that this is an old (i.e. <v6.28) issue? Can we then fix it in a patch release of 6.30 rather than blocking 6.30/00 for it?

[dpiparo]

Yes, we can, and in my opinion, should.