在Qt/C++中实现撤消功能(如Ctrl + Z)

class MyUndoCommand : public QUndoCommand {
public:
    MyUndoCommand(QObject *receiver, const QString &methodName, const QVariant &value);
    void undo() override;
    void redo() override;
private:
    QObject *m_receiver;
    QString m_methodName;
    QVariant m_value;
};

class MyWidget : public QWidget {
    Q_OBJECT
public:
    MyWidget(QWidget *parent = nullptr);
private:
    QLineEdit *m_lineEdit;
    QUndoStack *m_undoStack;
public slots:
    void setText(const QString &text);
};

MyWidget::MyWidget(QWidget *parent) : QWidget(parent) {
    m_lineEdit = new QLineEdit(this);
    m_undoStack = new QUndoStack(this);
    connect(m_lineEdit, &QLineEdit::textChanged, this, &MyWidget::setText);
}

void MyWidget::setText(const QString &text) {
    MyUndoCommand *command = new MyUndoCommand(m_lineEdit, "setText", text);
    m_undoStack->push(command);
}

MyUndoCommand::MyUndoCommand(QObject *receiver, const QString &methodName, const QVariant &value)
    : m_receiver(receiver), m_methodName(methodName), m_value(value) {
}

void MyUndoCommand::undo() {
    QMetaObject::invokeMethod(m_receiver, m_methodName.toStdString().c_str(), Qt::DirectConnection, Q_ARG(QVariant, m_value));
}

void MyUndoCommand::redo() {
    QMetaObject::invokeMethod(m_receiver, m_methodName.toStdString().c_str(), Qt::DirectConnection, Q_ARG(QVariant, m_value));
}

class MainWindow : public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *parent = nullptr);
private:
    MyWidget *m_myWidget;
protected:
    void keyPressEvent(QKeyEvent *event) override;
};

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent) {
    m_myWidget = new MyWidget(this);
    setCentralWidget(m_myWidget);
}

void MainWindow::keyPressEvent(QKeyEvent *event) {
    if (event->key() == Qt::Key_Z && event->modifiers() & Qt::ControlModifier) {
        if (event->modifiers() & Qt::ShiftModifier) {
            m_myWidget->m_undoStack->redo();
        } else {
            m_myWidget->m_undoStack->undo();
        }
    } else {
        QMainWindow::keyPressEvent(event);
    }
}