pyqt5 can't apply border to framelesswindow

Question

I applied border width and border color via setStyleSheet funciton in pyqt5. But when I use it in frameless window, border not applied. any issue in my code? I need help. Here comes my code.

import sys
from PyQt5.QtWidgets import QWidget,QApplication
from PyQt5.QtCore import Qt,QPoint

class CommonFramelessWidget(QWidget):
    def __init__(self,parent):
        super(CommonFramelessWidget,self).__init__(parent)
        self.setWindowFlags(Qt.Window|Qt.FramelessWindowHint)
        self.setStyleSheet('border:5px  black; background-color:red;')

    def mousePressEvent(self, event):
        self.oldPos = event.globalPos()
    def mouseMoveEvent(self,e):
        delta = QPoint (e.globalPos() - self.oldPos)
        self.move(self.x() + delta.x(), self.y() + delta.y())
        self.oldPos = e.globalPos()


if __name__ == "__main__":
    app = QApplication(sys.argv)
    mw = CommonFramelessWidget(None)
    mw.show()
    sys.exit(app.exec_())

Answer 1

You have to set the border type, in addition to activating the Qt::WA_StyledBackground attribute so that it uses the information of the stylesheet as the background style:

import sys
from PyQt5.QtWidgets import QWidget, QApplication
from PyQt5.QtCore import Qt, QPoint


class CommonFramelessWidget(QWidget):
    def __init__(self, parent=None):
        super(CommonFramelessWidget, self).__init__(parent)
        self.setWindowFlags(Qt.Window | Qt.FramelessWindowHint)
        self.setStyleSheet("border: 5px solid black; background-color:red;")
        self.setAttribute(Qt.WA_StyledBackground)

        self.resize(640, 480)

    def mousePressEvent(self, event):
        self.oldPos = event.globalPos()
        super(CommonFramelessWidget, self).mousePressEvent(event)

    def mouseMoveEvent(self, e):
        delta = QPoint(e.globalPos() - self.oldPos)
        self.move(self.pos() + delta)
        self.oldPos = e.globalPos()
        super(CommonFramelessWidget, self).mouseMoveEvent(e)


if __name__ == "__main__":
    app = QApplication(sys.argv)
    mw = CommonFramelessWidget()
    mw.show()
    sys.exit(app.exec_())