/// <summary>
/// Adds an operation to the undo buffer.
/// </summary>
/// <param name="operation">The operation.</param>
/// <remarks>
/// <para>
/// This methods needs to be called for every <see cref="IUndoableOperation"/> before or after
/// it is executed by calling its <see cref="IUndoableOperation.Do"/> method. Note:
/// <see cref="Add"/> does not execute the <see cref="IUndoableOperation"/> it will only record
/// the operation.
/// </para>
/// <para>
/// After the operation is recorded in the undo buffer it can be undone and redone by calling
/// <see cref="Undo"/> and <see cref="Redo"/>.
/// </para>
/// <para>
/// The recording of operations in the undo buffer can be temporarily disabled by setting
/// <see cref="AcceptChanges"/> to <see langword="false"/>.
/// </para>
/// </remarks>
/// <exception cref="ArgumentNullException">
/// <paramref name="operation"/> is <see langword="null"/>.
/// </exception>
/// <seealso cref="AcceptChanges"/>
public void Add(IUndoableOperation operation)
{
if (operation == null)
{
throw new ArgumentNullException("operation");
}
if (AcceptChanges)
{
InternalUndoStack.EnqueueHead(operation);
if (IsUndoGroupOpen)
{
_numberOfOperationsInGroup++;
}
if (InternalUndoStack.Count == 1)
{
OnPropertyChanged(new PropertyChangedEventArgs("CanUndo"));
}
ClearRedoStack();
if (!IsUndoGroupOpen)
{
EnforceSizeLimit();
}
}
}
private void ClearUndoStack()
{
if (InternalUndoStack.Count > 0)
{
InternalUndoStack.Clear();
OnPropertyChanged(new PropertyChangedEventArgs("CanUndo"));
}
}
void EnforceSizeLimit()
{
AssertNoUndoGroupOpen();
while (InternalUndoStack.Count > _sizeLimit)
{
InternalUndoStack.DequeueTail();
}
while (InternalRedoStack.Count > _sizeLimit)
{
InternalRedoStack.DequeueTail();
}
}
/// <summary>
/// Redoes the last undone operation.
/// </summary>
public void Redo()
{
AssertNoUndoGroupOpen();
if (InternalRedoStack.Count > 0)
{
IUndoableOperation operation = InternalRedoStack.DequeueHead();
InternalUndoStack.EnqueueHead(operation);
operation.Do();
OnOperationRedone();
if (InternalRedoStack.Count == 0)
{
OnPropertyChanged(new PropertyChangedEventArgs("CanRedo"));
}
if (InternalUndoStack.Count == 1)
{
OnPropertyChanged(new PropertyChangedEventArgs("CanUndo"));
}
EnforceSizeLimit();
}
}
