Black Window in PyQt5

PyQt5BlackWindow.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-
import sys

from PyQt5.QtCore import QPoint, Qt
from PyQt5.QtWidgets import QApplication, QPlainTextEdit, QMainWindow,  QLabel, QPushButton, QLineEdit

btn_size = 14

class MainWindow(QMainWindow):

    def __init__(self):
        super(MainWindow, self).__init__()
        self.setStyleSheet("QMainWindow {background: #2e3436;}")
        self.setMinimumSize(600,300)
        self.setWindowFlags(Qt.FramelessWindowHint)
        self.pressing = False
        
        self.title = QLabel("Window", self)
        self.title.setGeometry(0, 0, self.width(), 24)
        self.title.setAlignment(Qt.AlignCenter)
        self.title.setStyleSheet("background-color: #2e3436; color: #eeeeec; font-weight: bold;")
        
        self.btn_close = QPushButton("x", self)
        self.btn_close.setGeometry(5, 5, btn_size, btn_size)
        self.btn_close.clicked.connect(self.btn_close_clicked)
        self.btn_close.setFixedSize(btn_size,btn_size)
        self.btn_close.setStyleSheet("background: #cc0000; padding-bottom: 2px;")
        
        self.btn_min = QPushButton("-", self)
        self.btn_min.setGeometry(22, 5, btn_size, btn_size)
        self.btn_min.clicked.connect(self.btn_min_clicked)
        self.btn_min.setStyleSheet("background: #edd400;; padding-bottom: 2px;")
        
        self.btn_max = QPushButton("+", self)
        self.btn_max.setGeometry(39, 5, btn_size, btn_size)
        self.btn_max.clicked.connect(self.btn_max_clicked)
        self.btn_max.setFixedSize(btn_size, btn_size)
        self.btn_max.setStyleSheet("background: #73d216;; padding-bottom: 2px;")
        
        self.findfield = QLineEdit(self)
        self.findfield.setPlaceholderText("find ...")
        self.findfield.setGeometry(self.width() - 100, 5, 180, 22)
        self.findfield.setStyleSheet("background: #2e3436; color: #eeeeec; border: 1px solid #555753")

        self.start = QPoint(0, 0)
        self.pressing = False
        
        self.myeditor = QPlainTextEdit(self)
        self.myeditor.setGeometry(5, 20, self.width() - 10, self.height() - 32)
        self.myeditor.setStyleSheet("background: #2e3436; color: #eeeeec; border: 1px solid #555753")
        
    def btn_close_clicked(self):
        self.close()
        
    def btn_min_clicked(self):
        self.showMinimized()
        
    def btn_max_clicked(self):
        if self.windowState() == Qt.WindowMaximized:
            self.showNormal()
        else:
            self.showMaximized()

    def resizeEvent(self, QResizeEvent):
        super(MainWindow, self).resizeEvent(QResizeEvent)
        self.title.setFixedWidth(self.width())
        self.myeditor.setGeometry(5, 28, self.width() - 10, self.height() - 32)
        self.findfield.setGeometry(self.width() - 125, 5, 120, 22)

    def mousePressEvent(self, event):
        self.start = self.mapToGlobal(event.pos())
        self.pressing = True

    def mouseMoveEvent(self, event):
        if self.pressing:
            self.end = self.mapToGlobal(event.pos())
            self.movement = self.end-self.start
            self.setGeometry(self.mapToGlobal(self.movement).x(),
                                self.mapToGlobal(self.movement).y(),
                                self.width(),
                                self.height())
            self.start = self.end

    def mouseReleaseEvent(self, QMouseEvent):
        self.pressing = False


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