ConstraintLayout + VFL in Python -- "Finalizing but it still has children left"

Platform Language bindings
,
1

I converted the ConstraintLayout code from the gtk4-demo to Python, and it works well, but I get an error (“Finalizing… but it still has children left”) to stdout when I close the app.

The code is:

import gi
gi.require_version('Gtk', '4.0')
from gi.repository import Gtk

class ConstraintLayoutDemoWidget(Gtk.Widget):
    def __init__(self):
        super().__init__(hexpand=True, vexpand=True)

        self.constraint_layout_manager = Gtk.ConstraintLayout()
        self.set_layout_manager(self.constraint_layout_manager)

        self.button_1 = Gtk.Button(name='button1', label='Button 1')
        self.button_1.set_parent(self)
        self.button_2 = Gtk.Button(name='button2', label='Button 2')
        self.button_2.set_parent(self)
        self.button_3 = Gtk.Button(name='button3', label='Button 3')
        self.button_3.set_parent(self)

        vfl_constraints = [
            "H:|-[button1(==button2)]-12-[button2]-|",
            "H:|-[button3]-|",
            "V:|-[button1]-12-[button3(==button1)]-|",
            "V:|-[button2]-12-[button3(==button2)]-|",
        ]
        views = {'button1': self.button_1, 'button2': self.button_2, 'button3': self.button_3}
        self.constraint_layout_manager.add_constraints_from_description(vfl_constraints, hspacing=10, vspacing=10, views=views)


def on_activate(app):
    application_window = Gtk.ApplicationWindow(application=app)

    constraint_widget = ConstraintLayoutDemoWidget()

    box = Gtk.Box()
    box.append(constraint_widget)
    application_window.set_child(box)

    application_window.present()


if __name__ == '__main__':
    # Create a new application
    app = Gtk.Application(application_id='com.example.GtkApplication')
    app.connect('activate', on_activate)

    # Run the application
    app.run(None)

And the error is:

(python:1266308): Gtk-WARNING **: 18:12:28.256: Finalizing __main__+ConstraintLayoutDemoWidget 0x1a139a0, but it still has children left:
   - button1 0x1a079c0
   - button2 0x1a06670
   - button3 0x19c2990

I need to unparent the buttons from my widget when it’s being destroyed, but I’m not sure what method to override or signal to catch. Any suggestions?

2

maybe this helps

Greetings

3

This is a known limitation of the Python bindings: there is no way to override the dispose virtual function of GObject, which makes it hard to subclass GtkWidget. You can try and remove your widgets in the do_unroot() method, but you will need to recreate the widgets inside the do_root() method if you plan on moving your widget class between different parents.

4

Thanks for the quick responses!

I added a __del__ method to unparent the buttons, and that silences the warning. That may not be the best way, but…

import gi
gi.require_version('Gtk', '4.0')
from gi.repository import Gtk


#   +-----------------------------+
#   | +-----------+ +-----------+ |
#   | |  Child 1  | |  Child 2  | |
#   | +-----------+ +-----------+ |
#   | +-------------------------+ |
#   | |         Child 3         | |
#   | +-------------------------+ |
#   +-----------------------------+

class ConstraintLayoutDemoWidget(Gtk.Widget):
    def __init__(self):
        super().__init__(hexpand=True, vexpand=True)

        self.constraint_layout_manager = Gtk.ConstraintLayout()
        self.set_layout_manager(self.constraint_layout_manager)

        self.button_1 = Gtk.Button(name='button1', label='Button 1')
        self.button_1.set_parent(self)
        self.button_2 = Gtk.Button(name='button2', label='Button 2')
        self.button_2.set_parent(self)
        self.button_3 = Gtk.Button(name='button3', label='Button 3')
        self.button_3.set_parent(self)

        vfl_constraints = [
            "H:|-[button1(==button2)]-12-[button2]-|",
            "H:|-[button3]-|",
            "V:|-[button1]-12-[button3(==button1)]-|",
            "V:|-[button2]-12-[button3(==button2)]-|",
        ]
        views = {'button1': self.button_1, 'button2': self.button_2, 'button3': self.button_3}
        self.constraint_layout_manager.add_constraints_from_description(vfl_constraints, hspacing=10, vspacing=10, views=views)

    def __del__(self):
        self.button_1.unparent()
        self.button_2.unparent()
        self.button_3.unparent()


def on_activate(app):
    application_window = Gtk.ApplicationWindow(application=app)

    constraint_widget = ConstraintLayoutDemoWidget()

    box = Gtk.Box()
    box.append(constraint_widget)
    application_window.set_child(box)

    application_window.present()


if __name__ == '__main__':
    # Create a new application
    app = Gtk.Application(application_id='com.example.GtkApplication')
    app.connect('activate', on_activate)

    # Run the application
    app.run(None)
5

That’s also a viable solution, yes. It assumes that the Python wrapper will go away before the underlying C object, which is generally the case as the Python wrapper keeps the C object alive and is responsible for dropping the last reference on the object.

6

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.