File indexing completed on 2024-05-12 04:35:05

 /* This file is part of the TikZKit project.
  *
  * Copyright (C) 2013-2015 Dominik Haumann <dhaumann@kde.org>
  *
  * This library is free software; you can redistribute it and/or modify
  * it under the terms of the GNU Library General Public License as published
  * by the Free Software Foundation, either version 2 of the License, or
  * (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, see
  * <http://www.gnu.org/licenses/>.
  */
 
 #ifndef TIKZ_UNDO_ITEM_H
 #define TIKZ_UNDO_ITEM_H
 
 #include "tikz_export.h"
 
 #include <QString>
 #include <QJsonObject>
 
 namespace tikz {
 namespace core {
 
 class Document;
 class UndoGroup;
 class UndoItemPrivate;
 
 /**
  * Base class for undo/redo items.
  */
 class TIKZKITCORE_EXPORT UndoItem
 {
 public:
     /**
      * Constructor, setting the undo item's description to @p text,
      * and the associated tikz::core::document to @p doc.
      */
     UndoItem(const QString & text, Document* doc);
 
     /**
      * Virtual destructor.
      */
     virtual ~UndoItem();
 
     /**
      * Accessor to the tikz Document.
      */
     Document* document();
 
     /**
      * Set the undo item description to @p text.
      */
     void setText(const QString & text);
 
     /**
      * Returns the description of the undo item.
      */
     QString text() const;
 
     /**
      * Apply the redo operation.
      */
     virtual void redo() = 0;
 
     /**
      * Apply the undo operation.
      */
     virtual void undo() = 0;
 
     /**
      * Returns the uniq undo item identifier of this undo item.
      * Whenever two successive undo items have the same id, the function
      * mergeWith() is executed to fold the two undo items into a single
      * undo item.
      *
      * By default, -1 is returned. In this case (or any other negative id),
      * mergeWith() is not called.
      *
      * If you reimplement this function, reimplement it like this:
      * @code
      * int id() const override {
      *     return uniqId<decltype(this)>();
      * }
      * @endcode
      */
     virtual int id() const;
 
     /**
      * Merge @p item into this item. Afterwards, @p item is deleted.
      * Typically, the undo() operation is unchanged, and you only have to
      * copy the redo data of @p item into this undo item.
      */
     virtual bool mergeWith(const UndoItem * item);
 
 //
 // serialization
 //
 public:
     /**
      * Load the undo item state from the @p json object.
      */
     void load(const QJsonObject & json);
 
     /**
      * Serialize the undo item state to a JSON object.
      */
     QJsonObject save() const;
 
 protected:
     /**
      * Load the undo item state from the @p json object.
      */
     virtual void loadData(const QJsonObject & json) = 0;
 
     /**
      * Serialize the undo item state to a JSON object.
      */
     virtual QJsonObject saveData() const = 0;
 
 // group information
 public:
     /**
      * Retuns the UndoGroup this UndoItem belongs to.
      * As long as an UndoItem is not added to an undo group, a nullptr is
      * returned.
      */
     UndoGroup * group() const;
 
 protected:
     friend class UndoGroup;
     /**
      * Once an undo item is added to an UndoGroup, the undo group this item
      * belongs to is set to @p group. This function is called by the UndoGroup.
      */
     void setGroup(UndoGroup * group);
 
     /**
      * Internal id counter starting at 0.
      * Each time this function is called, the counter is increased by one.
      */
     static int nextFreeId();
 
     /**
      * Template function that always returns the same id for T.
      * This is a trick: Since the template funcion is generated for each class,
      * each undo item calling this function with its type gets an own uniq id.
      * Hence: We magically never get undo item id clashes at runtime.
      */
     template<typename T>
     int uniqId() const
     {
         static int s_id = nextFreeId();
         return s_id;
     }
 
 private:
     /**
      * Pimpl pointer to the held data.
      */
     UndoItemPrivate * const d;
 };
 
 }
 }
 
 #endif // TIKZ_UNDO_ITEM_H
 
 // kate: indent-width 4; replace-tabs on;