The detection only works for the simplest case where the method is at the last level in an inheritance hierarchy.

Based on a search of the repo, #1991 led me to https://github.com/sem-geologist/HussariX/blob/master/lib/ui/CustomPGWidgets.py#L98 which has a class that subclasses pg.ScaleBar.
The current detection technique would fail there.

@sem-geologist has been active in the issue tracker here before; hopefully this ping will get their attention

The detection would think that CustomScaleBar doesn't use the deprecated method parentChanged, not knowing whether any parent class does override.

It would then call self.parentChanged_() which would correctly invoke ScaleBar::parentChanged_().

It works in this case only because the parent (pyqtgraph) class was updated to use parentChanged_().

Hi @pijyoi

Thanks for the PR!. The diff looks good to me, but I'm a little hung up on the name, parentChanged_. The name does achieve the primary objective, which is to differentiate the method from the signal name, but the past-tense wording is in-line with the name of a signal. An alternative would be changeParent, but I'm not set on that. I'm open to other suggestions.

A contrived example where the current detection technique fails.

import pyqtgraph as pg 
from pyqtgraph.Qt import QtCore

class CustomParent(pg.GraphicsObject):
    def __init__(self):
        pg.GraphicsObject.__init__(self)
        self.text = "OLD PARENT"

    def boundingRect(self):
        return QtCore.QRectF(0, 0, 100, 100)

    def paint(self, p, *args):
        p.setPen(pg.mkPen('w'))
        p.drawText(0, 50, self.text)

    def parentChanged(self):
        self.text = "NEW PARENT"

class CustomChild(CustomParent):
    def __init__(self):
        CustomParent.__init__(self)
        self.text = "CHILD"

pg.mkQApp()
pw = pg.PlotWidget()
pw.show()
custom = CustomChild()
pw.addItem(custom)
pg.exec()

Maybe I have the wrong attitude about this, but I'm not so concerned about catching every usage of this method... this method is buried fairly deep in the library, and I wouldn't imagine that many end-users overwriting it...

Anyway, I'm fine w/ the current code diff.

I am generally unfamiliar with all the viewbox machinery. The docstring for parentChanged() says "It should generally be extended, not overridden.. And yet the only use of parentChanged() within the library (ScaleBar) doesn't call the parent method.

Maybe merge this "breaking" change after 0.13.0?

Since we just released 0.13.0, let's merge this one! Thanks for your work here @pijyoi