PyQt5 - in a QMainMenu, how to make a QWidget the parent (temporarily)?

Question

I have a QMainWindow that I initialize with a QWidget . I want that each Time I'll press the button New In my QMainWiindow , it will open the QWidget temporarily (in my case, until mouse button release).

I'm having trouble interacting QMainWindow with the QWidget . I tried many options, but it seemed like everything I tried tied the QWidget to the QMainWindow screen, and I don't want that.

It will be easier with an example:

TempWidgetMenu.py is my QMainWindow class. When I press New , a QWidget will appear, it Will color the screen gray-ish, and will color a rectangle from a button press, to the button release (like in windows snipping tool).

I Want that that every time I press on New , I'll be able to draw a rectangle from every point of the screen, and so it does the first time. When I press New for the second time (or afterwards), it will color everything but the main menu screen, and will not respond to the button actions.

I want the widget to be the "parent" of the program in the screen every time I press the button.

TempWidgetMenu.py (main):

import sys
from PyQt5.QtWidgets import QMainWindow, QApplication, QAction
from PyQt5.QtGui import QPixmap, QPainter
import TempWidget


class Menu(QMainWindow):

    def __init__(self):
        super().__init__()
        newAct = QAction('New', self)
        newAct.triggered.connect(self.new_image_window)
        self.toolbar = self.addToolBar('Exit')
        self.toolbar.addAction(newAct)
        self.opac_rect = TempWidget.TempOpacWidget()
        self.image = QPixmap("background.png")
        self.setGeometry(100, 100, 500, 300)
        self.resize(self.image.width(), self.image.height())
        self.show()

    def new_image_window(self):
        self.opac_rect.start()

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.drawPixmap(self.rect(), self.image)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    mainMenu = Menu()
    sys.exit(app.exec_())

TempWidget.py :

import tkinter as tk
from PyQt5 import QtWidgets, QtCore, QtGui


class TempOpacWidget(QtWidgets.QWidget):

    def __init__(self):
        super().__init__()
        root = tk.Tk()
        screen_width = root.winfo_screenwidth()
        screen_height = root.winfo_screenheight()
        self.setGeometry(0, 0, screen_width, screen_height)
        self.setWindowTitle(' ')
        self.begin = QtCore.QPoint()
        self.end = QtCore.QPoint()
        self.busy = False

    def start(self):

        self.busy = True
        self.setWindowOpacity(0.3)
        self.show()

    def paintEvent(self, event):
        if self.busy:
            brush_color = (128, 128, 255, 100)
            opacity = 0.3
        else:
            brush_color = (0, 0, 0, 0)
            opacity = 0

        self.setWindowOpacity(opacity)
        qp = QtGui.QPainter(self)
        qp.setBrush(QtGui.QColor(*brush_color))
        qp.drawRect(QtCore.QRectF(self.begin, self.end))

    def mousePressEvent(self, event):
        self.begin = event.pos()
        self.end = self.begin
        self.update()

    def mouseMoveEvent(self, event):
        self.end = event.pos()
        self.update()

    def mouseReleaseEvent(self, event):
        self.busy = False
        self.repaint()

I realize I'm initializing the TempOpacWidget once at the start. I want to initialize it only once, because it is doing the same thing.

How can I fix it, such that the TempOpacWidget will be the parent every time I call him?

Edit: If something is not clear, run the code it will make perfect sense. Press New , Choose a rectangle (with mouse), and then press New again to choose another rectangle, and you will understand what is the problem.

Answer 1

I do not quite understand what's going to happen, but I added and changed some lines of code. Click the New button and draw a rectangle. You should have new ideas. Good luck.

TempWidgetMenu.py

import sys
from PyQt5.QtWidgets import QMainWindow, QApplication, QAction
from PyQt5.QtGui     import QPixmap, QPainter
from PyQt5.QtCore    import Qt                             # +++
import TempWidget

class Menu(QMainWindow):
    def __init__(self):
        super().__init__()
        newAct = QAction('New', self)
        newAct.triggered.connect(self.new_image_window)
        self.toolbar = self.addToolBar('Exit')
        self.toolbar.addAction(newAct)

        self.opac_rect = TempWidget.TempOpacWidget(self)   # +++ self

        self.imageShow()                                   # +++  

    def imageShow(self):
        self.setWindowFlags(Qt.WindowStaysOnTopHint)       # +++ 

        self.image = QPixmap("background.png")
        self.setGeometry(100, 100, 500, 300)
        self.resize(self.image.width(), self.image.height())
        self.show()

    def new_image_window(self):
        self.opac_rect.start()

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.drawPixmap(self.rect(), self.image)

    # +++    
    def closeEvent(self, event):
        self.opac_rect.close()
        event.accept()


if __name__ == '__main__':
    app = QApplication(sys.argv)
    mainMenu = Menu()
    sys.exit(app.exec_())

TempWidget.py

import tkinter as tk
from PyQt5        import QtWidgets, QtCore, QtGui
from PyQt5.QtCore import Qt                                 # +++

class TempOpacWidget(QtWidgets.QWidget):

#    def __init__(self):
#        super().__init__()
    def __init__(self, parent=None):
        super(TempOpacWidget, self).__init__()              # no (parent)
        self.parent = parent                                # +++
        print("self=`{}`, \nparent=`{}`".format(self, self.parent))
        self.setWindowFlags(Qt.WindowStaysOnTopHint)        # +++

        root = tk.Tk()
        screen_width  = root.winfo_screenwidth()
        screen_height = root.winfo_screenheight()
        self.setGeometry(0, 0, screen_width, screen_height)
#        self.setWindowTitle('')
        self.begin = QtCore.QPoint()
        self.end   = QtCore.QPoint()
        self.busy  = False

    def start(self):
        self.setWindowFlags(Qt.WindowStaysOnTopHint)        # +++
        self.busy = True
        self.setWindowOpacity(0.5) # 0.3
        self.show()

    def paintEvent(self, event):
        if self.busy:
            brush_color = (128, 128, 255, 100)
            opacity = 0.5          # 0.3
        else:
            brush_color = (0, 0, 0, 0)

            opacity = 0.5          # 0       <<<---------
            # or try  `0`, how suits you !?  <<<---------
            #opacity = 0                    #<<<--------- 

        self.setWindowOpacity(opacity)
        qp = QtGui.QPainter(self)
        qp.setBrush(QtGui.QColor(*brush_color))
        qp.drawRect(QtCore.QRectF(self.begin, self.end))

    def mousePressEvent(self, event):
        #self.parent.hide()
        self.begin = event.pos()
        self.end   = self.begin
        self.update()

    def mouseMoveEvent(self, event):
        self.end = event.pos()
        self.update()

    def mouseReleaseEvent(self, event):
        print("def mouseReleaseEvent(self, event):---")
        self.busy = False
        self.repaint()
        self.parent.imageShow()                         # +++

Answer 2

If I understand you correctly, you want Menu.opac_rect to open in a separate window while your mouse button is pressed. I see a couple of issues with this. First, if you want a QWidget to open in a separate window, you should pass a Qt.windowFlags argument to the QWidget constructor, ie

self.opac_rect = TempWidget.TempOpacWidget(None, QtCore.Qt.Window)

Don't forget to import the QtCore namespace.

Secondly, QAction doesn't have the signals you need. Only objects that inherit from QWidget will have mousePressEvent and mouseReleaseEvent . If you must keep things in the toolbar, QToolBar has QToolBar.addWidget , so you could use a QLabel instead of QAction , and overwrite the necessary event handlers.

self.opac_rect = TempWidget.TempOpacWidget(None, QtCore.Qt.Window)
newAct = QLabel('New')
newAct.mousePressEvent = lambda e: self.opac_rect.start()
newAct.mouseReleaseEvent = lambda e: self.opac_rect.stop() # You'll need to write this
self.toolbar.addWidget(newAct)

You'll probably have to fiddle with the QLabel styling to make it look right, but I think this will accomplish what you are looking for.