Separation_item problem

[Juergen Reuter]

Hi,

I have been trying to fix the misplaced dot bug in Gregorian chant 
notation -- without sucess:

void
Vaticana_ligature_engraver::add_mora_column (Grob *parent)
{
  if (!parent) // empty ligature
    return;
  if (augmented_primitives_.size () == 0) // no dot for column
    return;
  Item *dotcol = make_item ("DotColumn", SCM_EOL);
  for (vsize i = 0; i < augmented_primitives_.size (); i++)
    {
      Item *dot = make_item ("Dots", augmented_primitives_[i]->self_scm ());
      dot->set_parent (augmented_primitives_[i], X_AXIS);
      dot->set_parent (parent, Y_AXIS);
      dot->set_property ("Y-offset", Grob::x_parent_positioning_proc);
      augmented_primitives_[i]->set_object ("dot", dot->self_scm ());
      Axis_group_interface::add_element (dotcol, dot);
      Side_position_interface::add_support (dot, augmented_primitives_[i]);
      Pointer_group_interface::add_grob (dot, ly_symbol2scm ("note-heads"),
                                         augmented_primitives_[i]);
      Dot_column::add_head (dotcol, augmented_primitives_[i]);
    }
}

The above code should create a dot column, which should be horizontally 
placed immediately behind Grob *parent.  The dot column should consist of 
a number of dots, one for each notehead grob held in the
vector<Item *> augmented_primitives_
variable.

The only thing that this code produces is a "Separation_item:  I've been 
drinking too much" error, and no dot is printed.

Once, when writing the porrectus engraver, I had similar problems, and as 
the cause, I suspected the discrepancy between the column of the music 
cause and the column of where to print the outcome.  This discrepancy is 
also true in the above code: the notehead, which is the cause of the dot, 
may arise earlier in time than the column where the dots are collected.

Has someone an idea how I can fix this problem?

Greetings,
Juergen