Develop Reference

Pushing QWidget Window to topmost in Python

I'm new to Python and have mostly learnt C# in the past. I am creating a QWidget class:
class Window(QWidget):
def __init__(self, gif, width, height):
super().__init__()
self.setGeometry(400, 200, width, height)
self.setWindowTitle("Python Run GIF Images")
self.setWindowIcon(QIcon('icons/qt.png'))
label = QLabel(self)
movie = QMovie(gif)
label.setMovie(movie)
movie.start()
And then define a function that creates a QApplication and then the Window:
def run_gif(gif, width, height):
app = QApplication([])
window = Window(gif, width, height)
window.show()
app.exec()
app.shutdown()
My issue is getting the gif to show topmost when it is launched. There is a Topmost property you can set on a Winform in C# which means no other window or other app you click on will cover the Window. This isn't essential but I want it to at least be shown above the code editor it is launched from so that the user doesn't have to select the Window to see the gif contained in the Window. I've spent hours looking at properties I can set either in the class or the method and not getting the result I need.
However, when I call the run_gif method for the second time, it does show it topmost, but along with the below exception (at least I think it's an exception from what I'm reading, it doesn't affect the running of the program other than printing to the console).
QApplication::regClass: Registering window class 'Qt640ScreenChangeObserverWindow' failed. (Class already exists.)
The only advice I can find on this error is not Python-specific and I don't really understand it. Maybe I'm being a bit ambitious for my early stage learning Python but not really seeing anything much on this error.
This is using PySide6.

Using setWindowFlag(Qt.WindowType.WindowStaysOnTopHint, True) seems to be working for me so far.
Example:
from PySide6.QtWidgets import *
from PySide6.QtCore import *
from PySide6.QtGui import *
class Window(QWidget):
def __init__(self, parent=None):
super().__init__(parent=parent)
self.layout = QVBoxLayout(self)
self.resize(200,100)
self.label = QLabel("Always on top...")
self.layout.addWidget(self.label)
self.setWindowFlag(Qt.WindowType.WindowStaysOnTopHint, True) # <--
if __name__ == '__main__':
app = QApplication([])
window = Window()
window.show()
app.exec()

PyQt5 Place QImage in a widget

I created a small GUI that allows me to draw a number. That number is supposed to be classified with a CNN. The CNN is not connected to this GUI yet. Will do that later on. I am still very new to PyQt5 and used some code that i found online for the drawing with QImage. It works, but at the moment i can draw all over the GUI. Is it possible to place that in a widget? So that I can only draw inside a specific frame and not all over the GUI?
So basically how can i get the self.image = QImage(...) iside a widget or something that i created earlier on my GUI? Is that possible somehow or would you even suggest to solve it in totaly different way?
import sys
from PyQt5 import QtWidgets
from PyQt5.QtGui import QIcon, QImage, QPainter, QPen, QBrush
from PyQt5.QtCore import Qt, QPoint
from UI.mainwindow_2 import Ui_MainWindow
import matplotlib.pyplot as plt
import numpy as np
class MainWindow(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
self.image = QImage(self.size(), QImage.Format_RGB32)
self.image.fill(Qt.white)
self.drawing = False
self.brushSize = 28
self.brushColor = Qt.black
self.lastPoint = QPoint()
self.ui.Clear.clicked.connect(self.clear)
def mousePressEvent(self, event):
if event.button() == Qt.LeftButton:
self.drawing = True
self.lastPoint = event.pos()
def mouseMoveEvent(self, event):
if(event.buttons() & Qt.LeftButton) & self.drawing:
painter = QPainter(self.image)
painter.setPen(QPen(self.brushColor, self.brushSize, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin))
painter.drawLine(self.lastPoint, event.pos())
self.lastPoint = event.pos()
self.update()
def mouseReleaseEvent(self, event):
if event.button() == Qt.LeftButton:
self.drawing = False
def paintEvent(self, event):
canvasPainter = QPainter(self)
canvasPainter.drawImage(self.rect(),self.image, self.image.rect())
def clear(self):
self.image.fill(Qt.white)
self.update()
def main():
app = QtWidgets.QApplication(sys.argv)
window = MainWindow()
window.show()
sys.exit(app.exec())
if __name__ == "__main__":
main()

First of all, the following aspects must be considered:
paint events are received by any (visible) QWidget subclass
painting is always constricted to the geometry of the widget
painting always happens from the bottom to the top, so whenever a widget has some children, whatever has been painted on that parent widget will be potentially covered by those children
So, the first thing to do is to implement the paintEvent only on the actual widget for which you want to paint. Since you're using Designer, this makes things a bit more complex, as there is no way to subclass a widget that already exists in an ui.
Luckily, Qt has a concept called "promoted widgets": it allows to "expand" a certain widget by specifying the custom subclass that will be actually used when the ui will be finally generated in the program.
choose which widget in your ui will be used for painting; I suggest you to start from a basic QWidget, I'll explain more about this later;
right click on it, and select "Promote to..." from the context menu;
in the "Promoted class name" type the exact class name you are going to use (let's say "Canvas");
in the "Header file" field, type the file name that will contain that class, as it would appear in an import statement (meaning that it should not have the py extension!); assuming you want to do everything in a single script and your script is named "mycanvas.py", type "mycanvas" in that field;
ensure that the "Base class name" combo is set to the exact class type of the widget you've chosen (QWidget, in this case, which is usually automatically selected)
click "Add" and then "Promote";
save the ui and generate the file with pyuic;
Now, the implementation of your mycanvas.py file is simple:
class Canvas(QtWidgets.QWidget):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.image = QImage(self.size(), QImage.Format_RGB32)
self.image.fill(Qt.white)
self.drawing = False
self.brushSize = 28
self.brushColor = Qt.black
self.lastPoint = QPoint()
# ... all the painting related methods, as you did in your code
class MainWindow(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
self.ui.Clear.clicked.connect(self.ui.canvas.clear)
def main():
# ...
Two considerations:
a QFrame usually has some borders, and since painting can always happen within the whole widget size, you might end up painting on the borders too. If you want a QFrame and paint inside that widget, then add a QWidget as a child to that frame and ensure that a layout is set for the frame;
setting the QImage size within the init is not a good approach, as the widget might change its size or it could be initialized with a size smaller than it will eventually have; you either set a fixed size in the __init__ before creating the QImage, or you keep track of the points/lines in an internal container and continuously draw the contents in the paintEvent;

Python PyQt5 how to show the full QMenuBar with a QWidget

I'm getting this weird result when using QMenuBar I've used this exact code before for the QMenuBar and it worked perfectly. But it doesn't show more than 1 QMenu
This is my code:
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
from PyQt5.QtGui import *
import sys
from functools import partial
class MainMenu(QWidget):
def __init__(self, parent = None):
super(MainMenu, self).__init__(parent)
# background = QWidget(self)
lay = QVBoxLayout(self)
lay.setContentsMargins(5, 35, 5, 5)
self.menu()
self.setWindowTitle('Control Panel')
self.setWindowIcon(self.style().standardIcon(getattr(QStyle, 'SP_DialogNoButton')))
self.grid = QGridLayout()
lay.addLayout(self.grid)
self.setLayout(lay)
self.setMinimumSize(400, 320)
def menu(self):
menubar = QMenuBar(self)
viewMenu = menubar.addMenu('View')
viewStatAct = QAction('Dark mode', self, checkable=True)
viewStatAct.setStatusTip('enable/disable Dark mode')
viewMenu.addAction(viewStatAct)
settingsMenu = menubar.addMenu('Configuration')
email = QAction('Set Email', self)
settingsMenu.addAction(email)
if __name__ == '__main__':
app = QApplication(sys.argv)
main = MainMenu()
main.show()
sys.exit(app.exec_())
Result:
I am aware that I am using QWidget when I should be using QMainWindow But is there a workaround???
(I apologize in advance for the terrible quality of the image, there is no good way to take a picture of a QMenuBar)

The problem is that with a QWidget you are not using the "private" layout that a QMainWindow has, which automatically resizes specific children widgets (including the menubar, the statusbar, the dock widgets, the toolbars and, obviously, the "centralWidget").
Remember that a QMainWindow has its own layout (which can't and shouldn't be changed), because it needs that specific custom layout to lay out the aforementioned widgets. If you want to set a layout for the main window, you'll need to apply it to its centralWidget.
Read carefully how the Main Window Framework behaves; as the documentation reports:
Note: Creating a main window without a central widget is not supported. You must have a central widget even if it is just a placeholder.
In order to work around that when using a basic QWidget, you'll have to manually resize the children widgets accordingly. In your case, you only need to resize the menubar, as long as you have a reference to it:
def menu(self):
self.menubar = QMenuBar(self)
# any other function has to be run against the *self.menubar* object
viewMenu = self.menubar.addMenu('View')
# etcetera...
def resizeEvent(self, event):
# calling the base class resizeEvent function is not usually
# required, but it is for certain widgets (especially item views
# or scroll areas), so just call it anyway, just to be sure, as
# it's a good habit to do that for most widget classes
super(MainMenu, self).resizeEvent(event)
# now that we have a direct reference to the menubar widget, we are
# also able to resize it, allowing all actions to be shown (as long
# as they are within the provided size
self.menubar.resize(self.width(), self.menubar.height())
Note: you can also "find" the menubar by means of self.findChild(QtWidgets.QMenuBar) or using the objectName, but using an instance attribute is usually an easier and better solution.

Set minimum width
self.setMinimumSize(320,240)

PyQt4: How to auto adjust size of a widget not in layout

I want to implement a GUI program like the blueprint editor in the Unreal game engine with PyQt4. Here is an example of the blueprint editor:
First I create a simple container widget to place all the components(The rectangles). In order to allow the user place the rectangles wherever they want(by drag & drop), I can't place my widgets in a layout. Then when the content of the rectangle is changed, the rectangle widget can't auto adjust the size itself.
Following is an example code:
import sys
from PyQt4 import QtCore
from PyQt4 import QtGui
class ChangeableChild(QtGui.QWidget):
def __init__(self, parent=None):
super(ChangeableChild, self).__init__(parent)
self.setLayout(QtGui.QVBoxLayout())
def addWidget(self, widget):
self.layout().addWidget(widget)
class MainWidget(QtGui.QWidget):
def __init__(self, child, parent=None):
super(MainWidget, self).__init__(parent)
child.setParent(self)
def main():
app = QtGui.QApplication(sys.argv)
changeable_child = ChangeableChild()
button = QtGui.QPushButton("Add label")
changeable_child.addWidget(button)
win = MainWidget(changeable_child)
win.show()
button.clicked.connect(
lambda: changeable_child.addWidget(QtGui.QLabel("A label.")))
app.exec_()
if __name__ == "__main__":
main()
When I hit "Add label" button to add a new label. The size of ChangeableChild wouldn't change automatically. If I put the ChangeableChild in a layout, it's all good.
So is there a way to auto adjust my widget when it's not in a layout? Or is there a way I can place my widget in a layout and still can place it in a absolute position?

Properly Positioning Popup Widgets in PyQt

his has plagued me for eons, mostly due to how many combinations of methodologies there are for moving widgets and whatnot. Essentially I have a simple widget that I'd like to be able to pop up in specific areas of my app. Problem is I can never seem to get it to pop up where I want it. Additionally, I'd like to set it up in a way where I can adjust the "pointer" side of it based on whether it's popping up to point at a widget in the top-left of the app versus, say, the bottom-right.
Ideally, I'd be able to place the popup nearly adjacent to the edges of the parent widget, and anchor it based on where it is. Here's what I've been trying.
from PyQt4.QtCore import *
from PyQt4.QtGui import *
import sys
class popup(QWidget):
def __init__(self, parent = None, widget=None):
QWidget.__init__(self, parent)
layout = QGridLayout(self)
button = QPushButton("Very Interesting Text Popup. Here's an arrow ^")
layout.addWidget(button)
self.move(widget.rect().bottomLeft())
class Window(QWidget):
def __init__(self):
QWidget.__init__(self)
self.button = QPushButton('Hit this button to show a popup', self)
self.button.clicked.connect(self.handleOpenDialog)
self.button.move(250, 50)
self.resize(600, 200)
def handleOpenDialog(self):
self.popup = popup(self, self.button)
self.popup.show()
if __name__ == '__main__':
app = QApplication(sys.argv)
win = Window()
win.show()
sys.exit(app.exec_())
This code generates a button that's randomly in the middle of the widget. What I'm trying to get is, in this example, the popup to show under the button with its "pivot" in the top right such that the arrow in the popup button would be pointing to the bottom right corner of the widget. However it's popping up in the top left of the Window instead. In all of my messing around with .move, .setGeometry, and playing with QRect, I can't for the life of me figure this out. Huge kudos to whoever can lend a hand. Thanks!

I know this is old, but I was searching for this recently and this is the best answer; I have a useful addition (for anyone else searching for this recipe!)
I implemented it as a mixin, which I think gives more flexibility to your dialogs:
class PopupDialogMixin(object): # will not work (with PySide at least) unless implemented as 'new style' class. I.e inherit from object
def makePopup(callWidget):
"""
Turns the dialog into a popup dialog.
callWidget is the widget responsible for calling the dialog (e.g. a toolbar button)
"""
self.setContentsMargins(0,0,0,0)
self.setWindowFlags(QtCore.Qt.FramelessWindowHint | QtCore.Qt.Popup)
self.setObjectName('ImportDialog')
# Move the dialog to the widget that called it
point = callWidget.rect().bottomRight()
global_point = callWidget.mapToGlobal(point)
self.move(global_point - QtCore.QPoint(self.width(), 0))
Your custom dialog would then inherit from both QtCore.QDialog and PopupDialogMixin. This gives you the option to use your dialog in the 'normal' way or make it a popup dialog. e.g:
dlg = MyDialog(self)
dlg.makePopup(self.myButton)
I think implementing it as a mixin gives a number of benefits:
No need to write the 'popup' code for each custom dialog you want as a popup
'Default' behaviour of the dialog is preserved - e.g. if you want to reuse it somewhere else as a 'regular' dialog, you just use it like normal
No need to pass anything extra to __init__ other than parent.

Here you go - the comments kind of explain the logic behind it - since the question is an example and about the positioning, I kept the rest of the code the same except the popup class, but just to mention cause its a pet peeve - you shouldn't import * (ever) but especially with something as big as PyQt4.QtCore/QtGui...
from PyQt4.QtCore import *
from PyQt4.QtGui import *
import sys
class popup(QWidget):
def __init__(self, parent = None, widget=None):
QWidget.__init__(self, parent)
layout = QGridLayout(self)
button = QPushButton("Very Interesting Text Popup. Here's an arrow ^")
layout.addWidget(button)
# adjust the margins or you will get an invisible, unintended border
layout.setContentsMargins(0, 0, 0, 0)
# need to set the layout
self.setLayout(layout)
self.adjustSize()
# tag this widget as a popup
self.setWindowFlags(Qt.Popup)
# calculate the botoom right point from the parents rectangle
point = widget.rect().bottomRight()
# map that point as a global position
global_point = widget.mapToGlobal(point)
# by default, a widget will be placed from its top-left corner, so
# we need to move it to the left based on the widgets width
self.move(global_point - QPoint(self.width(), 0))
class Window(QWidget):
def __init__(self):
QWidget.__init__(self)
self.button = QPushButton('Hit this button to show a popup', self)
self.button.clicked.connect(self.handleOpenDialog)
self.button.move(250, 50)
self.resize(600, 200)
def handleOpenDialog(self):
self.popup = popup(self, self.button)
self.popup.show()
if __name__ == '__main__':
app = QApplication(sys.argv)
win = Window()
win.show()
sys.exit(app.exec_())