Function that generates a stylesheet for styling QComboBox & QListView (popup list)

style_QComboBox.py

import sys
from qtpy import QtCore
from qtpy.QtWidgets import (
    QApplication,
    QMainWindow,
    QComboBox,
    QFrame,
    QGridLayout,
)


"""
menu-down.svg
```
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><title>menu-down</title><path d="M7,10L12,15L17,10H7Z" /></svg>
```

svg.qrc
```
<!DOCTYPE RCC>
<RCC version="1.0">
    <qresource prefix="/">
        <file>svg/menu-down.svg</file>
    </qresource>
</RCC>
```
"""

###  start of `svg.qrc` ###
qt_resource_data = b"\
\x00\x00\x00{\
<\
svg xmlns=\x22http:\
//www.w3.org/200\
0/svg\x22 viewBox=\x22\
0 0 24 24\x22><titl\
e>menu-down</tit\
le><path d=\x22M7,1\
0L12,15L17,10H7Z\
\x22 /></svg>\
"

qt_resource_name = b"\
\x00\x03\
\x00\x00z\xc7\
\x00s\
\x00v\x00g\
\x00\x0d\
\x01j\x5cg\
\x00m\
\x00e\x00n\x00u\x00-\x00d\x00o\x00w\x00n\x00.\x00s\x00v\x00g\
"

qt_resource_struct = b"\
\x00\x00\x00\x00\x00\x02\x00\x00\x00\x01\x00\x00\x00\x01\
\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x02\x00\x00\x00\x01\x00\x00\x00\x02\
\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x0c\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\
\x00\x00\x01\x8ep\x96\x03\xae\
"


def qInitResources():
    QtCore.qRegisterResourceData(
        0x03, qt_resource_struct, qt_resource_name, qt_resource_data
    )


def qCleanupResources():
    QtCore.qUnregisterResourceData(
        0x03, qt_resource_struct, qt_resource_name, qt_resource_data
    )


qInitResources()

###  end of `svg.qrc` ###


def style_QListView(
    border_color: str = "#404040",
    bg_color: str = "#fdfdfd",
    fg_color: str = "#404040",
    border_width: str = "1px",
    item_selected_bg_color: str = "#ACE2E1",
    item_selected_fg_color: str = "#008DDA",
):
    return f"""
    QListView {{
        background-color: {bg_color};
        color: {fg_color};
        border-width: {border_width};
        border-style: solid;
        border-color: {border_color};
        
    }}
    QListView::item:selected {{
        background-color: {item_selected_bg_color};
        color: {item_selected_fg_color};
    }}
    """


def style_QComboBox(
    border_color: str = "#b0b0b0",
    bg_color: str = "#fdfdfd",
    fg_color: str = "#404040",
    border_width: str = "1px",
    border_radius: str = "4px",
    horizontal_padding: str = "8px",
    vertical_padding: str = "2px",
    down_arrow_image: str = f":/svg/menu-down.svg",
    state_styles: dict[str, dict[str, str]] = {
        "hover": {
            "border-color": "#404040",
        },
        "on": {
            "border-color": "#404040",
            "border-bottom-left-radius": "0",
            "border-bottom-right-radius": "0",
        },
        "disabled": {
            "border-color": "#b0b0b0",
            "background-color": "#e0e0e0",
            "color": "#808080",
        },
    },
    drop_down_styles: dict[str, str] = {"background-color": "#e0e0e0"},
):

    qss = f"""
        QComboBox {{
            border-width: {border_width};
            border-style: solid;
            border-color: {border_color};
            border-radius: {border_radius};
            background-color: {bg_color};
            color: {fg_color};
            padding: {vertical_padding} {horizontal_padding};
        }}
        QComboBox::down-arrow {{
            image: url('{down_arrow_image}');
        }}
        QListView {{
            selection-background-color: #2020f0;
        }}
        """
    for state, styles in state_styles.items():
        rules = []
        for prop, value in styles.items():
            rules.append(f"{prop}: {value};")

        if rules:
            rules_str = "\n".join(rules)
            qss += f"""
            QComboBox:{state} {{
                {rules_str}
            }}
        """

    rules = []
    for prop, value in drop_down_styles.items():
        rules.append(f"{prop}: {value};")

    rules_str = "\n".join(rules)
    qss += f"""
        QComboBox::drop-down {{
            border-left-width: {border_width};
            border-left-style: solid;
            border-left-color: {border_color};
            border-top-right-radius: {border_radius};
            border-bottom-right-radius: {border_radius};
            color: {fg_color};
            {rules_str}
        }}
        """
    return qss


class Frame(QFrame):
    def __init__(self, parent=None):
        super().__init__(parent)
        layout = QGridLayout()
        layout.setSizeConstraint(QGridLayout.SizeConstraint.SetFixedSize)
        w = QComboBox()
        w.view().setStyleSheet(style_QListView())
        w.addItems(["Item1", "Item2", "Item3"])
        layout.addWidget(w, 0, 0)
        w = QComboBox()
        w.setDisabled(True)
        w.addItem("Item1")
        layout.addWidget(w, 0, 1)
        self.setLayout(layout)


def main():
    app = QApplication(sys.argv)
    app.setStyleSheet(style_QComboBox())
    w = QMainWindow()
    w.setMinimumSize(200, 100)
    w.setCentralWidget(Frame(w))
    w.show()
    sys.exit(app.exec())