lib/objchange.h

   1 /* Dia -- an diagram creation/manipulation program
   2  * Copyright (C) 1999 Alexander Larsson
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  */
  18
  19 /*! \file objchange.h -- Forming the basic of undo support to be implemented in objects */
  20 #ifndef OBJCHANGE_H
  21 #define OBJCHANGE_H
  22
  23 #include "diatypes.h"
  24
  25 typedef void (*ObjectChangeApplyFunc)(ObjectChange *change, DiaObject *obj);
  26 typedef void (*ObjectChangeRevertFunc)(ObjectChange *change, DiaObject *obj);
  27 typedef void (*ObjectChangeFreeFunc)(ObjectChange *change);
  28
  29 struct _ObjectChange {
  30   /*! If apply == transaction_point_pointer then this is a transaction
  31      point. Otherwise this is applying the change */
  32   ObjectChangeApplyFunc  apply;
  33   ObjectChangeRevertFunc revert; /*!< revert back to the state before the changed was applied */
  34   ObjectChangeFreeFunc   free; /*!< Remove extra data. Then this object is freed */
  35 };
  36
  37 /******** Helper functions of objects: *************/
  38
  39 struct _ObjectState {
  40   void (*free)(ObjectState *state); /*!< Frees pointers in the state,
  41                                        not called if NULL */
  42 };
  43
  44 /*!
  45   Gets the internal state from the object.
  46   This is used to snapshot the object state
  47   so that it can be stored for undo/redo.
  48
  49   Need not save state that only depens on
  50   the object and it's handles positions.
  51
  52   The calling function owns the returned reference.
  53 */
  54 typedef ObjectState * (*GetStateFunc) (DiaObject* obj);
  55
  56 /*!
  57   Sets the internal state from the object.
  58   This is used to snapshot the object state
  59   so that it can be stored for undo/redo.
  60
  61   The called function owns the reference and is
  62   responsible for freeing it.
  63 */
  64 typedef void (*SetStateFunc) (DiaObject* obj, ObjectState *state);
  65
  66
  67 ObjectChange *new_object_state_change(DiaObject *obj,
  68                                       ObjectState *old_state,
  69                                       GetStateFunc get_state,
  70                                       SetStateFunc set_state );
  71
  72 #endif /* OBJCHANGE_H */