QListWidget doesn't show custom widget lables - pyqt

Question

I'm trying to add custom RadioWidgets as QListWidgetItem to a QListWidget. The Mainwindow is shown and it seems radiowidget items are added but the labels are not shown. This is the code I'm using:
from typing import Optional
from PyQt5.QtWidgets import QLabel, QWidget
class RadioWidget(QWidget):
def __init__(self, parent: Optional[QWidget], radioTitle: str) -> None:
super().__init__(parent=parent)
self.radioTitleLbl = QLabel(radioTitle)
import sys
from typing import Optional
from PyQt5.QtWidgets import (
QApplication,
QListWidget,
QListWidgetItem,
QMainWindow,
QWidget,
)
from vagh.radiowidget import RadioWidget
class Vagh(QMainWindow):
def __init__(self, parent: Optional[QWidget] = None) -> None:
super().__init__(parent=parent)
self.radiosList = QListWidget(self)
self.radios = ("radio1", "radio2", "radio3")
self.loadRadios()
self.setCentralWidget(self.radiosList)
self.show()
def loadRadios(self):
for radio in self.radios:
radioItem = QListWidgetItem(self.radiosList)
radioWidget = RadioWidget(self.radiosList, radio)
radioItem.setSizeHint(radioWidget.sizeHint())
self.radiosList.addItem(radioItem)
self.radiosList.setItemWidget(radioItem, radioWidget)
if __name__ == "__main__":
app = QApplication(sys.argv)
v = Vagh()
app.exec_()

Answer 1

A widget that is created without any parent is considered a top level window (until it's reparented, for example when added to a layout).
Theoretically, the QLabel could be correctly added as a child by adding the RadioWidget instance as a parent in the constructor:
self.radioTitleLbl = QLabel(radioTitle, self)
But this won't work well: the label will be created on the top left of the radio widget, but that widget will know nothing about the label.
The sizeHint of a widget is returned based on its contents only when a layout manager is set for the widget (or when reimplemented in some way).
Since no layout manager is set for that widget, the result is that RadioWidget considers itself empty, returning an invalid hint (QSize(-1, -1)), and you will not see the label (nor the item) because the item is resized to a null size.
As usual, layout managers should always be used.
Not only: adding the label to a layout ensures that it correctly resizes itself whenever its text changes.
With the following modification you don't even need to set the sizeHint on the QListWidgetItem, as it will automatically use the hint returned by the widget:
class RadioWidget(QWidget):
def __init__(self, parent: Optional[QWidget], radioTitle: str) -> None:
super().__init__(parent=parent)
layout = QVBoxLayout(self)
self.radioTitleLbl = QLabel(radioTitle)
layout.addWidget(self.radioTitleLbl)