internal void StartUndoGroup(String description)
{
UndoGroup ug = new UndoGroup(this, description);
_currentUndoGroup = ug;
_actions.Push(ug);
}
internal void EndUndoGroup(bool keepChanges)
{
if (_currentUndoGroup == null)
{
return;
}
// group contains no items; or user doesn't want changes to part of undo
//
if (_currentUndoGroup.Count == 0 || !keepChanges)
{
UndoGroup ug = _actions.Pop() as UndoGroup; // get rid of the empty group
if (ug != _currentUndoGroup)
{
throw new Exception("Internal logic error: EndGroup doesn't match StartGroup");
}
}
_currentUndoGroup = null;
}