QOF  0.7.5
Undo: Track and undo or redo entity changes

Files

file  qofundo.h
 QOF undo handling.
 

Macros

#define QOF_MOD_UNDO   "qof-undo"
 

Functions

void qof_undo_set_param (QofEntity *ent, const QofParam *param, gchar *value)
 Set a value in this parameter of the entity. More...
 
void qof_undo_modify (QofInstance *inst, const QofParam *param)
 
void qof_undo_commit (QofInstance *inst, const QofParam *param)
 
void qof_undo_create (QofInstance *inst)
 
void qof_undo_delete (QofInstance *inst)
 
void qof_book_clear_undo (QofBook *book)
 Free the entire undo list for this book. More...
 
void qof_book_undo (QofBook *book)
 Set parameter values from before the previous event.
 
void qof_book_redo (QofBook *book)
 Set parameter values from after the previous event.
 
gboolean qof_book_can_undo (QofBook *book)
 event handler for undo widget More...
 
gboolean qof_book_can_redo (QofBook *book)
 event handler for redo widget More...
 
void qof_book_start_operation (QofBook *book, gchar *label)
 Start recording operation. More...
 
void qof_book_end_operation (QofBook *book)
 End recording the current operation.
 
QofTimeqof_book_undo_first_modified (QofBook *book)
 HIG compliance aid to report time of first change.
 
gint qof_book_undo_count (QofBook *book)
 Number of undo operations available.
 

Detailed Description

QOF Undo operates within a QofBook. In order to undo the changes to the entity, the initial state of each parameter is cached when an operation begins. If the entity changes are not successful, the lack of a qof_book_end_operation call before a qof_book_start_operation will cause the cached data to be freed. If the entity is changed successfully, qof_book_end_operation will create the undo data using the operation label and each of the entity changes that were successful.

Within each operation, entity changes can be recorded using QofEventHandler or individually.

  1. Only QOF parameter changes can be undone or redone. Data from structs that are not QOF objects or which have no QofParam to get and set the data will not be available to the undo process.
  2. Undo relates to 'user interface operations', not engine events. This is because an operation (like an import or voiding a transaction) can involve multiple, possibly conflicting, engine events - e.g. removing an entity from one reference and inserting it as another. Therefore, the UI developer alone can decide where an operation begins and ends. All changes between the two will be undone or redone in one call to qof_book_undo.
  3. Undo operations cannot be nested. Be careful where you start and end an undo operation, if your application calls qof_book_start_operation() before calling qof_book_end_operation(), the undo cache will be freed and QofUndo will not notify you of this. The API is designed to silently handle user aborts during a user operation. As undo data is cached when editing begins, if the edit is never completed the cache must be cleared before the next operation. i.e. if the user starts to edit an entity but then cancels the operation, there are no changes to undo. It follows that any one book can only be the subject of one operation at a time.
Since
0.7.0

Function Documentation

gboolean qof_book_can_redo ( QofBook book)

event handler for redo widget

Returns
FALSE if index_position == 0 or index_position == length otherwise TRUE.

Definition at line 442 of file qofundo.c.

443 {
444  QofUndo *book_undo;
445  gint length;
446 
447  book_undo = book->undo_data;
448  length = g_list_length (book_undo->undo_list);
449  if ((book_undo->index_position == length) || (length == 0))
450  return FALSE;
451  return TRUE;
452 }
gboolean qof_book_can_undo ( QofBook book)

event handler for undo widget

Returns
FALSE if length == 0 or index_position == 0, otherwise TRUE.

Definition at line 429 of file qofundo.c.

430 {
431  QofUndo *book_undo;
432  gint length;
433 
434  book_undo = book->undo_data;
435  length = g_list_length (book_undo->undo_list);
436  if ((book_undo->index_position == 0) || (length == 0))
437  return FALSE;
438  return TRUE;
439 }
void qof_book_clear_undo ( QofBook book)

Free the entire undo list for this book.

The application needs to decide whether to reset the undo list upon session_save, application close, user intervention etc.

Definition at line 409 of file qofundo.c.

410 {
411  QofUndoOperation *operation;
412  QofUndo *book_undo;
413 
414  if (!book)
415  return;
416  book_undo = book->undo_data;
417  while (book_undo != NULL)
418  {
419  operation = (QofUndoOperation *) book_undo->undo_list->data;
420  if(operation->entity_list)
421  g_list_free (operation->entity_list);
422  book_undo->undo_list = g_list_next (book_undo->undo_list);
423  }
424  book_undo->index_position = 0;
425  g_free (book_undo->undo_label);
426 }
void qof_book_start_operation ( QofBook book,
gchar *  label 
)

Start recording operation.

Definition at line 587 of file qofundo.c.

588 {
589  QofUndo *book_undo;
590 
591  book_undo = book->undo_data;
592  if (book_undo->undo_operation_open && book_undo->undo_cache)
593  {
594  g_list_free (book_undo->undo_cache);
595  book_undo->undo_operation_open = FALSE;
596  if (book_undo->undo_label)
597  g_free (book_undo->undo_label);
598  }
599  book_undo->undo_label = g_strdup (label);
600  book_undo->undo_operation_open = TRUE;
601 }
void qof_undo_commit ( QofInstance inst,
const QofParam param 
)
Mark this instance parameter after modification

Prepare undo data for this instance after committal. Record the modified state of this parameter of this instance so that if this operation is undone and then redone, the modification can be recreated.

Definition at line 571 of file qofundo.c.

572 {
573  QofUndoEntity *undo_entity;
574  QofUndo *book_undo;
575  QofBook *book;
576 
577  if (!instance || !param)
578  return;
579  book = instance->book;
580  book_undo = book->undo_data;
581  undo_entity = qof_prepare_undo (&instance->entity, param);
582  book_undo->undo_cache =
583  g_list_prepend (book_undo->undo_cache, undo_entity);
584 }
void qof_undo_create ( QofInstance inst)
prepare undo data for a new instance.

Record the creation of a new (empty) instance so that undo can delete it (and recreate it on redo).

Can be used within a QofEventHandler in response to QOF_EVENT_CREATE.

Definition at line 486 of file qofundo.c.

487 {
488  QofUndoEntity *undo_entity;
489  QofBook *book;
490  QofUndo *book_undo;
491 
492  if (!instance)
493  return;
494  book = instance->book;
495  book_undo = book->undo_data;
496  undo_entity = g_new0 (QofUndoEntity, 1);
497  // to undo a create, use a delete.
498  undo_entity->how = UNDO_DELETE;
499  undo_entity->guid = qof_instance_get_guid (instance);
500  undo_entity->type = instance->entity.e_type;
501  book_undo->undo_cache =
502  g_list_prepend (book_undo->undo_cache, undo_entity);
503 }
void qof_undo_delete ( QofInstance inst)
prepare undo data for an instance to be deleted.

Prepare for the deletion of an entity by storing ALL data in all editable parameters so that this delete operation can be undone.

Can be used within a QofEventHandler in response to QOF_EVENT_DESTROY, before the instance itself is deleted.

Definition at line 523 of file qofundo.c.

524 {
525  QofUndoEntity *undo_entity;
526  QofIdType type;
527  QofUndo *book_undo;
528  QofBook *book;
529 
530  if (!instance)
531  return;
532  book = instance->book;
533  book_undo = book->undo_data;
534  // now need to store each parameter in a second entity, MODIFY.
535  type = instance->entity.e_type;
536  qof_class_param_foreach (type, undo_get_entity, instance);
537  undo_entity = g_new0 (QofUndoEntity, 1);
538  // to undo a delete, use a create.
539  undo_entity->how = UNDO_CREATE;
540  undo_entity->guid = qof_instance_get_guid (instance);
541  undo_entity->type = type;
542  book_undo->undo_cache =
543  g_list_prepend (book_undo->undo_cache, undo_entity);
544 }
void qof_undo_modify ( QofInstance inst,
const QofParam param 
)
Mark this instance parameter before modification.

Prepare undo data for this parameter of this instance. Record the initial state of this parameter of this instance in preparation for modification so that undo can reset the value if required.

Definition at line 547 of file qofundo.c.

548 {
549  QofBook *book;
550  QofUndo *book_undo;
551  QofUndoEntity *undo_entity;
552 
553  if (!instance || !param)
554  return;
555  book = instance->book;
556  book_undo = book->undo_data;
557  // handle if record is called without a commit.
558  undo_entity = qof_prepare_undo (&instance->entity, param);
559  book_undo->undo_cache =
560  g_list_prepend (book_undo->undo_cache, undo_entity);
561  // set the initial state that undo will reinstate.
562  if (book_undo->index_position == 0)
563  {
564  book_undo->undo_list = g_list_prepend (book_undo->undo_list,
565  qof_undo_new_operation (book, "initial"));
566  book_undo->index_position++;
567  }
568 }
void qof_undo_set_param ( QofEntity ent,
const QofParam param,
gchar *  value 
)

Set a value in this parameter of the entity.

Setting an arbitrary parameter in an entity can involve repetitive string comparisons and setter function prototypes. This function accepts a QofParam (which determines the type of value) and a string representing the value. e.g. for a boolean, pass "TRUE", for a GUID pass the result of guid_to_string_buff.

Sets the undo data for this modification at the same time, calling qof_undo_modify, sets the parameter and qof_undo_commit.

Parameters
entAn initialised QofEntity from an accessible QofBook.
paramfrom qof_class_get_parameter
valueA string representation of the required value - original type as specified in param->param_type.

Definition at line 207 of file qofundo.c.

209 {
210  qof_undo_modify ((QofInstance*)ent, param);
211  set_param (ent, param, value);
212  qof_undo_commit ((QofInstance*)ent, param);
213 }