[PYTHON] The background color of the QWidget subclass cannot be set

The background color of the QWidget subclass cannot be set

As the title says. Solved. The solution is at the bottom of the article.

The background color of the Widget created from the QWidget subclass could not be set. However, when I tried the same with the inheritance source QWidget (), it worked for some reason.

What is this!

I looked it up, so I'll summarize it.

Reproduction code

# coding: utf-8

from PySide2 import QtWidgets, QtGui, QtCore


class Widget(QtWidgets.QWidget):
    def __init__(self):
        super(Widget, self).__init__()
        self.setStyleSheet("background-color:red")

        layout = QtWidgets.QVBoxLayout()

        button_widget = QtWidgets.QPushButton()
        button_widget.setText("Inherited widget")

        layout.addWidget(button_widget)

        self.setLayout(layout)


def generate_widget():
    parent_widget = QtWidgets.QWidget()
    parent_widget.setStyleSheet("background-color:red;")

    layout = QtWidgets.QVBoxLayout()

    button_widget = QtWidgets.QPushButton()
    button_widget.setText("QWidget")

    layout.addWidget(button_widget)

    parent_widget.setLayout(layout)

    return parent_widget


class Window(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()

        hbox = QtWidgets.QHBoxLayout()

        widget = Widget()
        widget2 = generate_widget()

        hbox.addWidget(widget)
        hbox.addWidget(widget2)

        self.setLayout(hbox)


def main():
    app = QtWidgets.QApplication()

    window = Window()
    window.show()

    exit(app.exec_())


if __name__ == "__main__":
    main()

Like this, the background color works only on the background of the button.

Nande?

The Qt Style Sheets Reference says: (Super translation)

QWidget

Only background, background-clip, and background-origin are supported.

** When subclassing from QWidget, you need to provide paintEvent as below. ** **

def paintEvent(self, event): opt = QtWidgets.QStyleOption() opt.init(self) painter = QtGui.QPainter(self) style = self.style() style.drawPrimitive(QtWidgets.QStyle.PE_Widget, opt, painter, self)

 So, if you put the above code in a subclass, it will be solved.
 You did it!

 ![qWidget_bgcolor_test_02.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/294868/05de106f-8322-b4d3-c8aa-c4794ce7a75c.png)