public List <IShape> OnUndo()
{
if (!IsStackEmpty())
{
ToRedoStack.Push(ToUndoStack.Pop());
var copy = ToUndoStack.Peek().Select(shape =>
shape is CompoundShape compoundShape ? GetAllCompoundShapeClones(compoundShape) : shape.Clone()
).ToList();
return(copy);
}
return(null);
}
private bool IsStackEmpty()
{
return(ToUndoStack.Count == 1 && ToUndoStack.Peek().Count == 0);
}