commands.h Example File

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 #ifndef COMMANDS_H
 #define COMMANDS_H

 #include <QUndoCommand>

 #include "diagramitem.h"

 class MoveCommand : public QUndoCommand
 {
 public:
     enum { Id = 1234 };

     MoveCommand(DiagramItem *diagramItem, const QPointF &oldPos,
                 QUndoCommand *parent = 0);

     void undo();
     void redo();
     bool mergeWith(const QUndoCommand *command);
     int id() const { return Id; }

 private:
     DiagramItem *myDiagramItem;
     QPointF myOldPos;
     QPointF newPos;
 };

 class DeleteCommand : public QUndoCommand
 {
 public:
     DeleteCommand(QGraphicsScene *graphicsScene, QUndoCommand *parent = 0);

     void undo();
     void redo();

 private:
     DiagramItem *myDiagramItem;
     QGraphicsScene *myGraphicsScene;
 };

 class AddCommand : public QUndoCommand
 {
 public:
     AddCommand(DiagramItem::DiagramType addType, QGraphicsScene *graphicsScene,
                QUndoCommand *parent = 0);
     ~AddCommand();

     void undo();
     void redo();

 private:
     DiagramItem *myDiagramItem;
     QGraphicsScene *myGraphicsScene;
     QPointF initialPosition;
 };

 QString createCommandString(DiagramItem *item, const QPointF &point);

 #endif