Qt：自定义枚举

用 Q_ENUM(enum) 就能供外部引用了：

https://blog.csdn.net/qq_43248127/article/details/119446455

imagewidget.h

enum BorderType
{
    TOP_BORDER,
    BOTTOM_BORDER,
    LEFT_BORDER,
    RIGHT_BORDER
};
Q_ENUM(BorderType)

imagewidget.cpp

void ImageWidget::deleteBlackBorder(BorderType border_type)
{
    qDebug() << border_type;
    switch (border_type) {
    case BorderType::TOP_BORDER:
        break;
    case BorderType::BOTTOM_BORDER:
        break;
    case BorderType::LEFT_BORDER:
        break;
    case BorderType::RIGHT_BORDER:
        break;
    }
}

mainwindow.cpp

void MainWindow::on_action_deleteBlackBorder_triggered()
{
    QDialog *dialog = new QDialog;
    dialog->setWindowTitle("去黑边");
    dialog->setFixedSize(400, 300);
    QGridLayout *gridLayout = new QGridLayout;
    QPushButton *pushButton_top = new QPushButton("上边");
    gridLayout->addWidget(pushButton_top, 0, 1);
    connect(pushButton_top, &QPushButton::clicked, [&](){
        imageWidget->deleteBlackBorder(imageWidget->BorderType::TOP_BORDER);
    });
    QPushButton *pushButton_left = new QPushButton("左边");
    gridLayout->addWidget(pushButton_left, 1, 0);
    connect(pushButton_left, &QPushButton::clicked, [&](){
        imageWidget->deleteBlackBorder(imageWidget->BorderType::LEFT_BORDER);
    });
    QPushButton *pushButton_right = new QPushButton("右边");
    gridLayout->addWidget(pushButton_right, 1, 2);
    connect(pushButton_right, &QPushButton::clicked, [&](){
        imageWidget->deleteBlackBorder(imageWidget->BorderType::RIGHT_BORDER);
    });
    QPushButton *pushButton_bottom = new QPushButton("下边");
    gridLayout->addWidget(pushButton_bottom, 2, 1);
    connect(pushButton_bottom, &QPushButton::clicked, [&](){
        imageWidget->deleteBlackBorder(imageWidget->BorderType::BOTTOM_BORDER);
    });
    dialog->setLayout(gridLayout);
    dialog->show();
}