src_gui_util_qundostack.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
#include <QUndoCommand>
 
//! [0]
class AppendText : public QUndoCommand
{
public:
    AppendText(QString *doc, const QString &text)
        : m_document(doc), m_text(text) { setText("append text"); }
    void undo() override
        { m_document->chop(m_text.length()); }
    void redo() override
        { m_document->append(m_text); }
    bool mergeWith(const QUndoCommand *other) override;
private:
    QString *m_document;
    QString m_text;
};
//! [0]
 
struct MyCommand : public QUndoCommand
{
    MyCommand() { setText("My Command"); }
    void undo() override {}
    void redo() override {}
    int id() const override { return 123; } // unique id for this command
};
 
struct InsertText : public QUndoCommand
{
    InsertText(QString *doc, int idx, const QString &text, QUndoCommand *parent = nullptr);
};
 
struct SetColor : public QUndoCommand
{
    SetColor(QString *doc, int idx, int len, const Qt::GlobalColor &color, QUndoCommand *parent = nullptr);
};
 
void examples(QUndoStack *stack, QString *document, int idx, const QString &text)
{
    {
        //! [1]
        MyCommand *command1 = new MyCommand();
        stack->push(command1);
        MyCommand *command2 = new MyCommand();
        stack->push(command2);
 
        stack->undo();
 
        MyCommand *command3 = new MyCommand();
        stack->push(command3); // command2 gets deleted
        //! [1]
    }
 
    {
        QUndoStack stack;
 
        //! [2]
        QUndoCommand *insertRed = new QUndoCommand(); // an empty command
        insertRed->setText("insert red text");
 
        new InsertText(document, idx, text, insertRed); // becomes child of insertRed
        new SetColor(document, idx, text.length(), Qt::red, insertRed);
 
        stack.push(insertRed);
        //! [2]
    }
}
 
//! [3]
bool AppendText::mergeWith(const QUndoCommand *other)
{
    if (other->id() != id()) // make sure other is also an AppendText command
        return false;
    m_text += static_cast<const AppendText*>(other)->m_text;
    return true;
}
//! [3]
 
void wrap( QUndoStack &stack, QString *document, int idx, const QString &text)
{
    //! [4]
    stack.beginMacro("insert red text");
    stack.push(new InsertText(document, idx, text));
    stack.push(new SetColor(document, idx, text.length(), Qt::red));
    stack.endMacro(); // indexChanged() is emitted
    //! [4]
 
 
    //! [5]
    QUndoCommand *insertRed = new QUndoCommand(); // an empty command
    insertRed->setText("insert red text");
 
    new InsertText(document, idx, text, insertRed); // becomes child of insertRed
    new SetColor(document, idx, text.length(), Qt::red, insertRed);
 
    stack.push(insertRed);
    //! [5]
}