public void Undo()
{
if (!history.CanUndo)
{
return;
}
HistoryAction action = history.Undo();
action.Undo(this);
}
public void Redo()
{
if (!history.CanRedo)
{
return;
}
HistoryAction action = history.Redo();
action.Redo(this);
}
public HistoryAction Redo()
{
if (!CanRedo)
{
throw new Exception("Cannot redo.");
}
HistoryAction action = redoStack.Pop();
undoStack.Push(action);
return(action);
}
public void Add(HistoryAction action)
{
if (!isActive)
{
return;
}
if (!TryMerge(action))
{
undoStack.Push(action);
}
redoStack.Clear();
}
private bool TryMerge(HistoryAction action)
{
if (!(action is IMergable))
{
return(false);
}
if (undoStack.Count == 0)
{
return(false);
}
if (!(undoStack.Peek() is IMergable))
{
return(false);
}
return((undoStack.Peek() as IMergable).Merge(action));
}
public bool Merge(HistoryAction action)
{
if (!(action is TextAction))
{
return(false);
}
TextAction newAction = (action as TextAction);
if (this.ActiveSheet != newAction.ActiveSheet)
{
return(false);
}
if (this.RowNumber != newAction.RowNumber)
{
return(false);
}
if (this.isTyping && newAction.isTyping &&
this.typingAtIndex + 1 == newAction.typingAtIndex && //typing continues from same position
this.NewText[typingAtIndex] != ' ') //break action at space
{
this.NewText = newAction.NewText;
this.typingAtIndex = newAction.typingAtIndex;
return(true);
}
if (this.isDeleting && newAction.isDeleting &&
this.deletingAtIndex - 1 == newAction.deletingAtIndex && //deleting continues from same position
this.PreviousText[deletingAtIndex] != ' ') //break action at space
{
this.NewText = newAction.NewText;
this.deletingAtIndex = newAction.deletingAtIndex;
return(true);
}
return(false);
}
