- Qt 5.5
- Qt Widgets
- Undo Framework Example
- commands.cpp Example File
- Qt 5.5.1 Reference Documentation

# commands.cpp Example File

tools/undoframework/commands.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
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    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
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    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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    #include <QtWidgets>

    #include "commands.h"
    #include "diagramitem.h"

    MoveCommand::MoveCommand(DiagramItem *diagramItem, const QPointF &oldPos,
                     QUndoCommand *parent)
        : QUndoCommand(parent)
    {
        myDiagramItem = diagramItem;
        newPos = diagramItem->pos();
        myOldPos = oldPos;
    }

    bool MoveCommand::mergeWith(const QUndoCommand *command)
    {
        const MoveCommand *moveCommand = static_cast<const MoveCommand *>(command);
        DiagramItem *item = moveCommand->myDiagramItem;

        if (myDiagramItem != item)
        return false;

        newPos = item->pos();
        setText(QObject::tr("Move %1")
            .arg(createCommandString(myDiagramItem, newPos)));

        return true;
    }

    void MoveCommand::undo()
    {
        myDiagramItem->setPos(myOldPos);
        myDiagramItem->scene()->update();
        setText(QObject::tr("Move %1")
            .arg(createCommandString(myDiagramItem, newPos)));
    }

    void MoveCommand::redo()
    {
        myDiagramItem->setPos(newPos);
        setText(QObject::tr("Move %1")
            .arg(createCommandString(myDiagramItem, newPos)));
    }

    DeleteCommand::DeleteCommand(QGraphicsScene *scene, QUndoCommand *parent)
        : QUndoCommand(parent)
    {
        myGraphicsScene = scene;
        QList<QGraphicsItem *> list = myGraphicsScene->selectedItems();
        list.first()->setSelected(false);
        myDiagramItem = static_cast<DiagramItem *>(list.first());
        setText(QObject::tr("Delete %1")
            .arg(createCommandString(myDiagramItem, myDiagramItem->pos())));
    }

    void DeleteCommand::undo()
    {
        myGraphicsScene->addItem(myDiagramItem);
        myGraphicsScene->update();
    }

    void DeleteCommand::redo()
    {
        myGraphicsScene->removeItem(myDiagramItem);
    }

    AddCommand::AddCommand(DiagramItem::DiagramType addType,
                           QGraphicsScene *scene, QUndoCommand *parent)
        : QUndoCommand(parent)
    {
        static int itemCount = 0;

        myGraphicsScene = scene;
        myDiagramItem = new DiagramItem(addType);
        initialPosition = QPointF((itemCount * 15) % int(scene->width()),
                                  (itemCount * 15) % int(scene->height()));
        scene->update();
        ++itemCount;
        setText(QObject::tr("Add %1")
            .arg(createCommandString(myDiagramItem, initialPosition)));
    }

    AddCommand::~AddCommand()
    {
        if (!myDiagramItem->scene())
            delete myDiagramItem;
    }

    void AddCommand::undo()
    {
        myGraphicsScene->removeItem(myDiagramItem);
        myGraphicsScene->update();
    }

    void AddCommand::redo()
    {
        myGraphicsScene->addItem(myDiagramItem);
        myDiagramItem->setPos(initialPosition);
        myGraphicsScene->clearSelection();
        myGraphicsScene->update();
    }

    QString createCommandString(DiagramItem *item, const QPointF &pos)
    {
        return QObject::tr("%1 at (%2, %3)")
            .arg(item->diagramType() == DiagramItem::Box ? "Box" : "Triangle")
            .arg(pos.x()).arg(pos.y());
    }