QComboBox边框在有背景颜色时更改

#include <QApplication>
#include <QComboBox>
#include <QVBoxLayout>
#include <QWidget>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);

    QWidget window;
    QVBoxLayout *layout = new QVBoxLayout(&window);

    QComboBox *comboBox = new QComboBox();
    comboBox->addItem("Option 1");
    comboBox->addItem("Option 2");
    comboBox->addItem("Option 3");

    // 设置背景颜色
    comboBox->setStyleSheet("QComboBox { background-color: #f0f0f0; }");

    // 设置边框样式
    comboBox->setStyleSheet(comboBox->styleSheet() + 
        "QComboBox {"
        "    border: 2px solid #333;"
        "    border-radius: 5px;"
        "}"
        "QComboBox::drop-down {"
        "    subcontrol-origin: padding;"
        "    subcontrol-position: top right;"
        "    width: 15px;"
        "    border-left-width: 1px;"
        "    border-left-color: darkgray;"
        "    border-left-style: solid;"
        "    border-top-right-radius: 3px;"
        "    border-bottom-right-radius: 3px;"
        "}");

    layout->addWidget(comboBox);
    window.show();

    return app.exec();
}