CheckableComboBox.py

""" Checkable ComboBox implementation taken from:
https://gis.stackexchange.com/questions/350148/qcombobox-multiple-selection-pyqt5 
and modified to work with pyqt6 """

from PyQt6.QtCore import (
    Qt,
    QEvent,
    
)
from PyQt6.QtWidgets import (
    QComboBox,
    QStyledItemDelegate,
    QApplication,
    QPushButton,
    
)
from PyQt6.QtGui import (
    QStandardItem,
    QFontMetrics,
    QPalette,
    QMouseEvent,
)


class CheckableComboBox(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)
        # Make the lineedit the same color as QPushButton
        # palette = QApplication.palette(QPushButton())
        # palette.setBrush(QPalette.base(), palette.button())
        # self.lineEdit().setPalette(palette)
        self.lineEdit().setPalette(QApplication.palette(QPushButton()))
        
        # Use custom delegate
        self.setItemDelegate(CheckableComboBox.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

        # Prevent popup from closing when clicking on an item
        self.view().viewport().installEventFilter(self)

    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 toggleItem(self, index, enable=True):
        """ Enable the item at index index """
        
        if index < self.count():
            item = self.model().item(index)
            if enable:
                item.setCheckState(Qt.CheckState.Checked)
            else:
                item.setCheckState(Qt.CheckState.Unchecked)
    
    def toggleItems(self, indices, enable=True):
        for index in indices:
            self.toggleItem(index, enable)

    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, checked=False):
        item = QStandardItem()
        item.setText(text)
        if data is None:
            item.setData(text)
        else:
            item.setData(data)
            
        # item.setFlags(Qt.ItemIsEnabled | Qt.ItemIsUserCheckable)
        # item.setData(Qt.Unchecked, Qt.CheckStateRole)
        # self.model().appendRow(item)

        item.setFlags(Qt.ItemFlag.ItemIsEnabled | Qt.ItemFlag.ItemIsUserCheckable)
        if checked:
            item.setData(Qt.CheckState.Checked, Qt.ItemDataRole.CheckStateRole)
        else:
            item.setData(Qt.CheckState.Unchecked, Qt.ItemDataRole.CheckStateRole)
        #self.addItem(text, data)
        self.model().appendRow(item)
        # self.model().insertRow(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):
        # Return the list of selected items data
        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