QComboBox checkbox indicator overwrites left of Item text in Windows11 pyqt6 but not on Ubuntu

[VolkerH]

I am using a 'CheckableComboBox' widget in Python pyqt6, which works fine in Ubuntu, but in Windows 11 the ComboBox indicator seems to be hard coded to overwrite the left edge of the Item text. If you use a CSS style to vary the padding, right and left offsets etc. of the indicator then the styled indicator moves around as you program it to, but the displayed item text in the GUI has a locked in blank overlay at its left edge as though there is a default checkbox lurking there.

Code -

-- coding: utf-8 --

From https://gis.stackexchange.com/questions/350148/qcombobox-multiple-selection-pyqt5

import sys
from PyQt6.QtCore import Qt, QEvent
from PyQt6.QtGui import QStandardItem, QFontMetrics
from PyQt6.QtWidgets import ( QComboBox, QStyledItemDelegate,
QSizePolicy,
QApplication,
QMainWindow,
QWidget )

class MultiComboBox(QComboBox):
# Subclass Delegate to increase item height
class Delegate(QStyledItemDelegate):
def sizeHint(self, option, index):
size = super().sizeHint(option, index)
size.setHeight(20)
return size

def __init__(self, *args, **kwargs):
    super().__init__(*args, **kwargs)

    # Make the combo editable to set a custom text, but readonly
    self.setEditable(True)
    self.lineEdit().setReadOnly(True)

    # Use custom delegate
    self.setItemDelegate(MultiComboBox.Delegate())

    # Update the text when an item is toggled
    self.model().dataChanged.connect(self.updateText)

    # Hide and show popup when clicking the line edit
    self.lineEdit().installEventFilter(self)
    self.closeOnLineEditClick = False

def resizeEvent(self, event):
    # Recompute text to elide as needed
    self.updateText()
    super().resizeEvent(event)

def eventFilter(self, object, event):
    if object == self.lineEdit():
        if event.type() == QEvent.Type.MouseButtonRelease:
            if self.closeOnLineEditClick:
                self.hidePopup()
            else:
                self.showPopup()
            return True
        return False

    if object == self.view().viewport():
        if event.type() == QEvent.Type.MouseButtonRelease:
            index = self.view().indexAt(event.pos())
            item = self.model().item(index.row())

            if item.checkState() == Qt.CheckState.Checked:
                item.setCheckState(Qt.CheckState.Unchecked)
            else:
                item.setCheckState(Qt.CheckState.Checked)
            return True
    return False

def showPopup(self):
    super().showPopup()
    # When the popup is displayed, a click on the lineedit should close it
    self.closeOnLineEditClick = True

def hidePopup(self):
    super().hidePopup()
    # Used to prevent immediate reopening when clicking on the lineEdit
    self.startTimer(100)
    # Refresh the display text when closing
    self.updateText()

def timerEvent(self, event):
    # After timeout, kill timer, and reenable click on line edit
    self.killTimer(event.timerId())
    self.closeOnLineEditClick = False

def updateText(self):
    texts = []
    for i in range(self.model().rowCount()):
        if self.model().item(i).checkState() == Qt.CheckState.Checked:
            texts.append(self.model().item(i).text())
    text = ", ".join(texts)

    # Compute elided text (with "...")
    metrics = QFontMetrics(self.lineEdit().font())
    elidedText = metrics.elidedText(text, Qt.TextElideMode.ElideRight, self.lineEdit().width())
    self.lineEdit().setText(elidedText)

def addItem(self, text, data=None):
    item = QStandardItem()
    item.setText(text)
    if data is None:
        item.setData(text)
    else:
        item.setData(data)
    item.setFlags(Qt.ItemFlag.ItemIsEnabled | Qt.ItemFlag.ItemIsUserCheckable)
    item.setData(Qt.CheckState.Unchecked, Qt.ItemDataRole.CheckStateRole)
    self.model().appendRow(item)

def addItems(self, texts, datalist=None):
    for i, text in enumerate(texts):
        try:
            data = datalist[i]
        except (TypeError, IndexError):
            data = None
        self.addItem(text, data)

def currentData(self):
    res = []
    for i in range(self.model().rowCount()):
        if self.model().item(i).checkState() == Qt.CheckState.Checked:
            res.append(self.model().item(i).data())
    return res

def currentOptions(self):
    res = []
    for i in range(self.model().rowCount()):
        if self.model().item(i).checkState() == Qt.CheckState.Checked:
            res.append((self.model().item(i).text(),
                        self.model().item(i).data()))
    return res

comunes = ['Ameglia', 'Arcola', 'Bagnone', 'Bolano', 'Melbourne', 'Othertown' ]
cStyle = """
QComboBox QAbstractItemView{ background-color: #ccccff; border: 1px solid yellow; }
QAbstractItemView::indicator{ border: 1px solid blue; background-color: transparent; }
QAbstractItemView::indicator:checked{ border: 1px solid red; background-color: orange; }
"""
cStyleWithOffset = """
QComboBox QAbstractItemView{ background-color: #ccccff; border: 1px solid yellow; padding-left: 20px; }
QAbstractItemView::indicator{ border: 1px solid blue; background-color: transparent; left: -10px; }
QAbstractItemView::indicator:checked{ border: 1px solid red; background-color: orange; }
"""
qtApp = QApplication( sys.argv )
qWin = QMainWindow()
combo = MultiComboBox( parent=qWin )
combo.addItems( comunes )
combo.setMinimumWidth( 300 )

combo.setStyleSheet( cStyle )

combo.setStyleSheet( cStyleWithOffset )
qWin.show()
qtApp.exec()

[Christian Ehrlicher]

What exact Qt version do you use?
I would guess it's 6.7.0 or similar with the new windows11 style which has some bugs. Either upgrade to 6.8.x or use the windowsvista style in between.