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PyQt6 deleting custom widget with nested class causes the program to crash

I am using Python 3.9.5.
I have encountered some serious problem in my project and here is a minimum reproducible example code, along with some descriptions.
from PyQt6.QtCore import *
from PyQt6.QtGui import *
from PyQt6.QtWidgets import *
class Editor(QTextEdit):
doubleClicked = pyqtSignal(QTextEdit)
def __init__(self):
super().__init__()
self.setReadOnly(True)
def mouseDoubleClickEvent(self, e: QMouseEvent) -> None:
self.doubleClicked.emit(self)
class textcell(QGroupBox):
def __init__(self, text):
super().__init__()
self.setAlignment(Qt.AlignmentFlag.AlignLeft | Qt.AlignmentFlag.AlignTop)
self.label = QLabel(text)
self.apply = makebutton('Apply')
self.apply.hide()
self.editor = Editor()
self.editor.doubleClicked.connect(lambda: self.editor.setReadOnly(False))
self.editor.doubleClicked.connect(self.apply.show)
self.hbox = QHBoxLayout()
self.hbox.addSpacerItem(spacer)
self.hbox.addWidget(self.apply)
self.vbox = QVBoxLayout()
self.vbox.addWidget(self.label)
self.vbox.addWidget(self.editor)
self.vbox.addLayout(self.hbox)
self.setLayout(self.vbox)
self.apply.clicked.connect(self.on_ApplyClick)
def on_ApplyClick(self):
self.editor.setReadOnly(True)
self.apply.hide()
def makebutton(text):
button = QPushButton()
button.setFixedSize(60, 20)
button.setText(text)
return button
class songpage(QGroupBox):
def __init__(self, texts):
super().__init__()
self.init(texts)
self.setCheckable(True)
self.setChecked(False)
def init(self, texts):
self.vbox = QVBoxLayout()
artist = textcell('Artist')
artist.editor.setText(texts[0])
album = textcell('Album')
album.editor.setText(texts[1])
title = textcell('Title')
title.editor.setText(texts[2])
self.vbox.addWidget(artist)
self.vbox.addWidget(album)
self.vbox.addWidget(title)
self.setLayout(self.vbox)
spacer = QSpacerItem(0, 20, QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Minimum)
class Ui_MainWindow(QMainWindow):
def __init__(self):
super().__init__()
self.resize(405, 720)
self.setWindowTitle('example')
frame = self.frameGeometry()
center = self.screen().availableGeometry().center()
frame.moveCenter(center)
self.move(frame.topLeft())
self.centralwidget = QWidget(self)
vbox = QVBoxLayout(self.centralwidget)
hbox = QHBoxLayout()
add = makebutton('Add')
delete = makebutton('Delete')
hbox.addWidget(add)
hbox.addSpacerItem(spacer)
hbox.addWidget(delete)
vbox.addLayout(hbox)
self.scrollArea = QScrollArea(self.centralwidget)
self.scrollArea.setWidgetResizable(True)
self.scrollAreaWidgetContents = QWidget()
self.scrollArea.setVerticalScrollBarPolicy(Qt.ScrollBarPolicy.ScrollBarAlwaysOn)
self.verticalLayout = QVBoxLayout(self.scrollAreaWidgetContents)
self.verticalLayout.setAlignment(Qt.AlignmentFlag.AlignTop)
self.scrollArea.setWidget(self.scrollAreaWidgetContents)
self.scrollArea.setAlignment(Qt.AlignmentFlag.AlignLeft | Qt.AlignmentFlag.AlignTop)
vbox.addWidget(self.scrollArea)
self.setCentralWidget(self.centralwidget)
add.clicked.connect(self.addObj)
delete.clicked.connect(self.deleteObj)
def addObj(self):
Obj = songpage(('AAA', 'BBB', 'CCC'))
self.verticalLayout.addWidget(Obj)
def deleteObj(self):
item = self.verticalLayout.itemAt(0)
widget = item.widget()
self.verticalLayout.removeItem(item)
self.verticalLayout.removeWidget(widget)
app = QApplication([])
window = Ui_MainWindow()
window.show()
app.exec()
The problem is very simple, if I click add button, the widget will be added and everything works fine, if I double click on a QTextEdit, its apply button will show and it will change from read only to editable.
After I click an apply button, the button will hide and the corresponding QTextEdit will be read only again.
I have finally managed to add a doubleClicked signal to QTextEdit.
And, the problem, is if I click delete button, instead of deleting the thing as expected, it crashes the whole application.
I am sorry the minimum reproducible example is so long, but I have only managed to reproduce the issue with all the code and I really don't know what went wrong.
So how to fix it?

Well, I have figured it out, it was caused by the spacer item that I add to every one of horizontal layouts where fixed-sized buttons are used.
All such layouts are using the same spacer item, exactly the same spacer item, not just identical.
From what I have observed, the spacer items are all references to the same object, they are all echos of the same object which lives at a fixed memory address.
I honestly don't understand how such thing works, that the same object can not only be added to multiple layouts and present in all the layouts concurrently, but also be added to the same layout multiple times, yet it always remains the original object, not duplicates of itself.
I thought when I added the same spacer item to multiple layouts, I didn't add the original spacer item, instead duplicates of the original item which are identical but are at different memory addresses, and clearly that isn't how Python works.
So when I remove a widget, everything inside it, everything inside its layout is deleted, and the spacer item is deleted.
Because all the spacer items in all the layouts are references to the original spacer item, when I delete one of the layouts, the original spacer item is deleted as well, and the spacer item is deleted from all other layouts, yet its shadows remain, and the item isn't properly removed from all the other layouts, the layouts contain references to an object that no longer exists, thus the application crashed.
By removing the definition of the spacer item and replacing adding the spacer item with .addStretch(), the bug is fixed.

PyQt Image(pixmap) gets cropped when other content changes width in a widget

I'm making a table-like widget that displays an image, the file name, and two box-selection areas. I have two objects 'grid_row' & 'grid_table' (both using QGridLayout), grid_row being a single row and grid_table containing x number of grid_rows (I'm designing it like this because it's simply easier to keep track of my custom properties).
The tool looks like this
The final layout is a QVBoxLayout, then from top to bottom, I have QHBoxLayout(the one with a label and combobox), grid_row(for the headers 1,2,3), a scroll_area that contains the grid_table with each one being grid_rows. Lastly another QHBoxLayout for the buttons.
Each grid_row contains a 'image-widget', and two region labels(QLabel). The image widget contains a label(I used setPixmap for display) and a pushbutton. Here are my grid_row and image_widget classes:
class grid_row(QWidget):
def __init__(self, parent=None):
super().__init__()
#self.frame = frame_main()
self.grid_layout = QGridLayout()
self.grid_layout.setSpacing(50)
self.image_widget = image_widget()
self.grid_layout.addWidget(self.image_widget, 0, 0, 1, 1, Qt.AlignHCenter)
self.region_2 = QLabel('null')
self.grid_layout.addWidget(self.region_2, 0, 2, 1, 1, Qt.AlignHCenter)
self.setLayout(self.grid_layout)
self.region_1 = QLabel('null')
self.grid_layout.addWidget(self.region_1, 0, 1, 1, 1, Qt.AlignHCenter)
class image_widget(QWidget):
def __init__(self, parent=None):
super().__init__()
self.initUI()
def initUI(self):
self.setAcceptDrops(True)
self.image_widget_layout = QHBoxLayout()
self.image_widget_label = QLabel()
self.image_widget_label.setPixmap(QPixmap('default.png').scaled(96, 54))
self.image_widget_layout.addWidget(self.image_widget_label)
self.img_btn = QPushButton()
self.img_btn.setEnabled(False)
self.img_btn.setText('Drag Here!')
self.image_widget_layout.addWidget(self.img_btn)
self.setLayout(self.image_widget_layout)
if __name__ == '__main__':
app = QApplication(sys.argv)
widget = QWidget()
layout = QVBoxLayout()
grid_row = grid_row()
layout.addWidget(grid_row)
btn = QPushButton('press')
btn.clicked.connect(lambda: grid_row.region_1.setText('[0,0,1920,1080]'))
layout.addWidget(btn)
widget.setLayout(layout)
scroll_area = QScrollArea()
scroll_area.setWidget(widget)
scroll_area.show()
sys.exit(app.exec_())
So currently, I've implemented events that allow me to drag images into the image_widget and click the push button to modify the two regions that are framed (format: [x1, y1, x2, y2]). The problem is that when I do that(e.g. region values go from 'null' to say '[20,20, 500, 500]', the image gets squished because now the labels are taking up more width.
I realize that some size policy needs to be set (and maybe other properties) but I don't know which property to use and on which widget. I want the image to remain the same. Maybe stretch out the width of each column for the grid_row?
To clarify, I want the label containing the pixmap to remain the same size (always 96*54) and fully displayed(not cropped or stretched) at all times.
I've provided the a simplified executable code to display my problem, the classes are the same as my code, I just only put grid_row inside the scroll_area and added a button to change one of the values of the region to simulate the situation. Can provide additional code if needed. Thanks in advance!

Wow sometimes the answer is really one extra line of code...
So the documentation mentions that QScrollArea by default honors the size of its widget. Which is why when I changed the region (to a value that's wider/ more text) the widget does not auto adjust.
I needed to add
scroll_area.setWidgetResizable(True)
to allow the widget to resize wider thus prompting the scroll bars to appear. This way my pixmap image doesn't get cropped from not having enough space.

The easiest way would be to add size constraints to the label before adding to the layout
self.image_widget_label.adjustSize()
self.image_widget_label.setFixedSize(self.image_widget_label.size())
self.image_widget_layout.addWidget(self.image_widget_label)
adjustSize would resize the label depending on the contents.
The more difficult way is to answer the questions :
"when I change the size of the overall window, how do I want this
particular item to behave? When the window is at its minimal size,
which items do I want hidden or out of view? When the window is full
size, where do I want empty spots?"
To answer these better read a bit on Qt Layout management

Qt5: How do I make the window scroll instead of expand as rows are added to QFormLayout? (Python 3)

I have a window set up like this:
vbox = QVBoxLayout()
groupBox = QGroupBox()
formLayout = QFormLayout()
groupBox.setLayout(formLayout)
vbox.addWidget(groupBox)
I also have two buttons that add rows and remove rows from formLayout.
When I add too many rows such that they cannot fit in the defined window, the window expands vertically. When rows are deleted, the window remains at the expanded size.
I instead want to have the area scroll such that the new rows are only visible within the defined window size, and such that the window does not expand unless the user expands it manually. How can I add a scrolling feature to this and prevent the window from expanding?

I've figured it out. You can use QScrollArea(), as below:
vbox = QVBoxLayout()
groupBox = QGroupBox()
formLayout = QFormLayout()
groupBox.setLayout(formLayout)
scroll_area = QScrollArea()
scroll_area.setWidgetResizeable(True)
scroll_area.setWidget(groupBox)
vbox.addWidget(scroll_area)
This creates a window that doesn't change its size, but rather automatically adds a scroll bar when more rows are added to formLayout.

Positioning widgets to QBoxLayout

I'm using PySide to build a GUI
I have a QBoxLayout that I have add some Widgets to, the problem is I want control their positions which I was not able to do, I tried what have been provided in the documentation page which is
addWidget( widg, int streatch, int alignment)
but it is not giving me what I want so the final look that I want is something like this
------------------------------------------------------------ ^^ **
&&&&&&
if the line ____ represents the whole window/ layout
I would like the widget which I named wid in my code to be like the dashed line --------
and the sliders to be in the same place as ^^
and finally the button to be in &&&&&
My second question is I want to add some labels to the sliders and to the como-box and I would like to determine the position how can I do that
here is my code
self.wid = GLWidget()
mainLayout = QtGui.QHBoxLayout()
mainLayout.addWidget(self.wid)
self.xSlider = self.createSlider()
self.ySlider = self.createSlider()
mainLayout.addWidget(self.xSlider)
mainLayout.addWidget(self.ySlider)
self.btn = QtGui.QPushButton('OK')
self.btn.resize(self.btn.sizeHint())
mainLayout.addWidget(self.btn)
self.combo = QtGui.QComboBox()
mainLayout.addWidget(self.combo)
self.setLayout(mainLayout)
self.setWindowTitle(self.tr("Hello GL"))
self.setGeometry(350, 350, 1000, 1000)

You could use a QGridLayout instead of QHBoxLayout and use QGridLayout's setColumnMinimumWidth method to dictate your required widget width.Like that:
mainLayout = QtGui.QGridLayout()
mainLayout.setColumnMinimumWidth(0, 100) #set column 0 width to 100 pixels
button = QtGui.QPushButton('OK')
mainLayout.addWidget(button, 0, 0) #adds the button to the widened column
and then continue to add the rest of the widgets.

pyqt: how to remove elements from a QVBoxLayout?

I want a multi-color selection widget. The way I'm doing it is having a "+" button, and an initially empty vbox. When + is pressed, it adds a QHBoxLayout to the vbox containing a "-" button and 3 spinboxes. When the "-" button is pressed I want that row to disappear and everything to go back to looking like it did before that row was added. The code I currently have is:
vbox = self.ui.color_layout #from QtDesigner
hbox = QtGui.QHBoxLayout()
remove = QtGui.QPushButton("-", parent=self)
remove.clicked.connect(lambda: vbox.removeItem(hbox))
rspin = QtGui.QSpinBox(parent=self)
gspin = QtGui.QSpinBox(parent=self)
bspin = QtGui.QSpinBox(parent=self)
hbox.addWidget(remove)
hbox.addWidget(QtGui.QLabel("R:", parent=self))
hbox.addWidget(rspin)
hbox.addWidget(QtGui.QLabel("G:", parent=self))
hbox.addWidget(gspin)
hbox.addWidget(QtGui.QLabel("B:", parent=self))
hbox.addWidget(bspin)
vbox.addLayout(hbox)
Adding widgets works fine. However, removing them results in a really messed-up looking thing where the row isn't actually removed, but the spacing is all messed up.
What am I doing wrong?
EDIT: The docs say, for removeWidget:
After this call, it is the caller's responsibility to give the widget a reasonable geometry or to put the widget back into a layout.
How do I do that? (I come from a GTK background...)
EDIT 2: I even kept track of the rows and called the takeAt function to remove it, but it still gets messed up. What gives? It looks like the layout is removed but none of the widgets are...
EDIT 3: this also doesn't work, just messes things up in a similar way:
vbox = self.ui.color_layout
hbox = QtGui.QHBoxLayout()
row_widget = QtGui.QWidget(parent=self) #dummy widget to hold this stuff
remove = QtGui.QPushButton("-", parent=self)
def remove_func():
vbox.removeWidget(row_widget)
remove.clicked.connect(remove_func)
rspin = QtGui.QSpinBox(parent=self)
gspin = QtGui.QSpinBox(parent=self)
bspin = QtGui.QSpinBox(parent=self)
hbox.addWidget(remove)
hbox.addWidget(QtGui.QLabel("R:", parent=self))
hbox.addWidget(rspin)
hbox.addWidget(QtGui.QLabel("G:", parent=self))
hbox.addWidget(gspin)
hbox.addWidget(QtGui.QLabel("B:", parent=self))
hbox.addWidget(bspin)
row_widget.setLayout(hbox)
vbox.addWidget(row_widget)

Try removing from parent widget, not the layout.
QLayout is not a parent, the parent for widgets being laid out is actually layout's parent. For more info and a clearer explanation see documentation on Qt layouts.
To remove widget, set its parent to None like this:
widget = QWidget()
layout = QVBoxLayout()
btn = QPushButton("To be removed")
layout.addWidget(btn)
widget.setLayout(layout)
# later
btn.setParent(None)