title: PyQt5 draggable frameless window
body: <p>I found an example to set borders on a frameless window, however it's not draggable. How can I  make a frameless window draggable? Especially if I can see an example it'll be awesome. Here is my example code(normally the code is longer, that's why there are much libraries just don't mind them);</p>
  
  <pre><code>from PyQt5.QtWidgets import (QMessageBox,QApplication, QWidget, QToolTip, QPushButton,
                               QDesktopWidget, QMainWindow, QAction, qApp, QToolBar, QVBoxLayout,
                               QComboBox,QLabel,QLineEdit,QGridLayout,QMenuBar,QMenu,QStatusBar,
                               QTextEdit,QDialog,QFrame,QProgressBar
                               )
  from PyQt5 import QtCore, QtWidgets, QtGui
  from PyQt5.QtGui import QIcon,QFont,QPixmap,QPalette
  from PyQt5.QtCore import QCoreApplication, Qt,QBasicTimer
  
  import sys
  
  class cssden(QMainWindow):
      def __init__(self):
          super().__init__()
  
  
          self.mwidget = QMainWindow(self)
          self.setWindowFlags(QtCore.Qt.FramelessWindowHint)
  
  
          #size
          self.setFixedSize(320, 450)
          self.center
  
  
          #label
          self.lbl = QLabel(self)
          self.lbl.setText("test")
          self.lbl.setStyleSheet("background-color: rgb(0,0,0);"
                                 "border: 1px solid red;"
                                 "color: rgb(255,255,255);"
                                 "font: bold italic 20pt 'Times New Roman';")
          self.lbl.setGeometry(5,5,60,40)
  
          self.show()
  
      #center
      def center(self):
          qr = self.frameGeometry()
          cp = QDesktopWidget().availableGeometry().center()
          qr.moveCenter(cp)
          self.move(qr.topLeft())
  
  app = QApplication(sys.argv)
  app.setStyleSheet("QMainWindow{background-color: darkgray;border: 1px solid black}")
  
  ex = cssden()
  sys.exit(app.exec_())
  </code></pre>