Qt:防止在子部件上拖放，并显示禁止的光标

#include <QtWidgets>

class MyWidget : public QWidget {
public:
    MyWidget(QWidget *parent = nullptr) : QWidget(parent) {
        setAcceptDrops(true);
    }

protected:
    void dragEnterEvent(QDragEnterEvent *event) override {
        if (event->mimeData()->hasFormat("text/plain")) {
            event->acceptProposedAction();
        } else {
            event->ignore();
        }
    }

    void dragMoveEvent(QDragMoveEvent *event) override {
        if (event->mimeData()->hasFormat("text/plain")) {
            event->acceptProposedAction();
        } else {
            event->ignore();
        }
    }

    void dropEvent(QDropEvent *event) override {
        if (event->mimeData()->hasFormat("text/plain")) {
            // 处理拖放数据
            QString text = event->mimeData()->text();
            // ...
            event->acceptProposedAction();
        } else {
            event->ignore();
        }
    }

    void mousePressEvent(QMouseEvent *event) override {
        if (event->button() == Qt::LeftButton) {
            // 设置禁止的光标
            setCursor(Qt::ForbiddenCursor);
        } else {
            QWidget::mousePressEvent(event);
        }
    }
};

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

    MyWidget widget;
    widget.show();

    return app.exec();
}