private void ApplyState(HistoryState state)
 {
     gridWidth  = state.GridWidth;
     gridHeight = state.GridHeight;
     Pixels.Reset(state.GetGridClone());
     OnPropertyChanged("GridHeight");
     OnPropertyChanged("GridWidth");
     OnPropertyChanged("PixelWidth");
     OnPropertyChanged("Pixels");
     OnPropertyChanged("UndoAction");
     OnPropertyChanged("RedoAction");
     OnPropertyChanged("CanUndo");
     OnPropertyChanged("CanRedo");
 }