How to paint() with QStyledItemDelegate

I am using PySide2 and I cant find any documentation on how to use the paint() function in a QStyledItemDelegate subclass. I am rather new to classes but is so far understandable but having trouble with PySide2.

I would like to replace my QtWidgets.QListWidgetItem with my own ListWidgetItem and display them correctly, like this:

So on the left of the ListWidgetItem an icon a bit to the right the name of the ListWidgetItem and underneath the description.

Here is the code:

from PySide2 import QtWidgets, QtCore, QtGui
from PySide2.QtGui import *
import sys

class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__()

        self.setWindowTitle('Test Window')
        self.setStyleSheet("background-color: rgb(65, 65, 65);")

        mainWidget = QtWidgets.QWidget(self)
        self.setCentralWidget(mainWidget)
        self.boxLayout = QtWidgets.QVBoxLayout()
        mainWidget.setLayout(self.boxLayout)

        # Add Widgets
        self.textField = QtWidgets.QLineEdit()
        self.listView = QtWidgets.QListWidget()

        self.textField.textChanged.connect(self.onTextChanged)

        self.boxLayout.addWidget(self.textField)
        self.boxLayout.addWidget(self.listView)

        self.textField.setFocus()


    def onTextChanged(self, ):
        titles = ['Monkey', 'Giraffe', 'Dragon', 'Bull']
        descriptions = ['Almost a homo sapiens sapiens', 'I am a Giraffe!', 'Can fly and is hot on spices', 'Horny...']

        if self.textField.text() == '' or self.textField.text().isspace() or self.textField.text() == ' ':
            if self.listView.count() > 0:
                self.listView.clear()
        else:
            if self.listView.count() > 0:
                self.listView.clear()
            for x in range(len(titles)):
                if self.textField.text() in titles[x]:
                    item = ListWidgetItem(titles[x])
                    self.listView.addItem(item)
                    self.listView.setCurrentRow(0)
                    continue


class ListWidgetItem(QtWidgets.QListWidgetItem):
    def __init__(self, title = '', description = '', icon = QtGui.QIcon()):
        super(ListWidgetItem, self).__init__()
        self.title = title
        self.description = description
        self.icon = icon


class ListViewStyle(QtWidgets.QStyledItemDelegate):
    def __init__(self, parent, itemModel):
        super(ListViewStyle, self).__init__(parent)
        self.itemModel = itemModel

    def sizeHint(self, option, index):
        if index:
            return QtCore.QSize(40, 40)

    def paint(self, painter, option, index):
        super(ListViewStyle, self).paint(painter, option, index)

if __name__ == '__main__':
    app = QtWidgets.QApplication.instance()
    if app is None: 
        app = QtWidgets.QApplication(sys.argv)

    w = MainWindow()
    w.show()
    #sys.exit(app.exec_())

Info: In onTextChanged() the ListWidgetItem will be added to the QListWidget but not drawn correctly, basically empty.

Does QListWidgetItem have any notable difference to QListView?

The delegate only paints and is not interested in what element provides the information since that class uses the QModelIndex and the same model to obtain the information, so in my previous solution I used a QStandardItemModel that uses QStandardItem and in your current case a QListWidget with QListWidgetItem is indifferent. My delegate expects only that the information of the title, description and icon are related to TitleRole, DescriptionRole and IconRole, respectively.

On the other hand it is not good to delete the items but it is better to hide or make them visible when necessary.

Considering the above, the solution with QListWidget is as follows:

import sys

from PySide2 import QtWidgets, QtCore, QtGui

TitleRole = QtCore.Qt.UserRole + 1000
DescriptionRole = QtCore.Qt.UserRole + 1001
IconRole = QtCore.Qt.UserRole + 1002


class ListWidgetItem(QtWidgets.QListWidgetItem):
    def __init__(self, title="", description="", icon=QtGui.QIcon()):
        super(ListWidgetItem, self).__init__()
        self.title = title
        self.description = description
        self.icon = icon

    @property
    def title(self):
        return self.data(TitleRole)

    @title.setter
    def title(self, title):
        self.setData(TitleRole, title)

    @property
    def description(self):
        return self.data(DescriptionRole)

    @description.setter
    def description(self, description):
        self.setData(DescriptionRole, description)

    @property
    def icon(self):
        return self.data(IconRole)

    @icon.setter
    def icon(self, icon):
        self.setData(IconRole, icon)


class StyledItemDelegate(QtWidgets.QStyledItemDelegate):
    def sizeHint(self, option, index):
        return QtCore.QSize(50, 50)

    def paint(self, painter, option, index):
        super(StyledItemDelegate, self).paint(painter, option, index)
        title = index.data(TitleRole)
        description = index.data(DescriptionRole)
        icon = index.data(IconRole)

        mode = QtGui.QIcon.Normal
        if not (option.state & QtWidgets.QStyle.State_Enabled):
            mode = QtGui.QIcon.Disabled
        elif option.state & QtWidgets.QStyle.State_Selected:
            mode = QtGui.QIcon.Selected

        state = (
            QtGui.QIcon.On
            if option.state & QtWidgets.QStyle.State_Open
            else QtGui.QIcon.Off
        )
        iconRect = QtCore.QRect(option.rect)
        iconRect.setSize(QtCore.QSize(40, 40))
        icon.paint(
            painter, iconRect, QtCore.Qt.AlignLeft | QtCore.Qt.AlignVCenter, mode, state
        )

        titleFont = QtGui.QFont(option.font)
        titleFont.setPixelSize(20)
        fm = QtGui.QFontMetrics(titleFont)
        titleRect = QtCore.QRect(option.rect)
        titleRect.setLeft(iconRect.right())
        titleRect.setHeight(fm.height())

        color = (
            option.palette.color(QtGui.QPalette.BrightText)
            if option.state & QtWidgets.QStyle.State_Selected
            else option.palette.color(QtGui.QPalette.WindowText)
        )
        painter.save()
        painter.setFont(titleFont)
        pen = painter.pen()
        pen.setColor(color)
        painter.setPen(pen)
        painter.drawText(titleRect, title)
        painter.restore()

        descriptionFont = QtGui.QFont(option.font)
        descriptionFont.setPixelSize(15)
        fm = QtGui.QFontMetrics(descriptionFont)
        descriptionRect = QtCore.QRect(option.rect)
        descriptionRect.setTopLeft(titleRect.bottomLeft())
        descriptionRect.setHeight(fm.height())
        painter.save()
        painter.setFont(descriptionFont)
        pen = painter.pen()
        pen.setColor(color)
        painter.setPen(pen)
        painter.drawText(
            descriptionRect,
            fm.elidedText(description, QtCore.Qt.ElideRight, descriptionRect.width()),
        )
        painter.restore()


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__()

        self.setWindowTitle("Test Window")
        self.setStyleSheet("background-color: rgb(65, 65, 65);")

        mainWidget = QtWidgets.QWidget(self)
        self.setCentralWidget(mainWidget)
        self.boxLayout = QtWidgets.QVBoxLayout()
        mainWidget.setLayout(self.boxLayout)

        # Add Widgets
        self.textField = QtWidgets.QLineEdit()
        self.listView = QtWidgets.QListWidget()

        self.textField.textChanged.connect(self.onTextChanged)

        self.boxLayout.addWidget(self.textField)
        self.boxLayout.addWidget(self.listView)
        self.fill_model()

        self.textField.setFocus()

        self.listView.setItemDelegate(StyledItemDelegate(self))

    def fill_model(self):
        titles = ["Monkey", "Giraffe", "Dragon", "Bull"]
        descriptions = [
            "Almost a homo sapiens sapiens",
            "I am a Giraffe!",
            "Can fly and is hot on spices",
            "Horny...",
        ]

        for title, description in zip(titles, descriptions):
            it = ListWidgetItem(title=title, description=description)
            self.listView.addItem(it)

    @QtCore.Slot(str)
    def onTextChanged(self, text):
        text = text.strip()
        if text:
            for i in range(self.listView.count()):
                it = self.listView.item(i)
                if it is not None:
                    it.setHidden(text.lower() not in it.title.lower())
        else:
            for i in range(self.listView.count()):
                it = self.listView.item(i)
                if it is not None:
                    it.setHidden(False)


if __name__ == "__main__":
    app = QtWidgets.QApplication.instance()
    if app is None:
        app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())