.. _Printing Protocol:

Printing Protocol
=================

The protocol for delegating how a :class:`graphtage.TreeNode` or :class:`graphtage.Edit` is printed in
:meth:`graphtage.GraphtageFormatter.print` is as follows:

#. Determine the actual object to be printed:
    * If ``node_or_edit`` is an :class:`graphtage.Edit`:
        * If ``with_edits``, then choose the edit
        * Otherwise, choose :attr:`node_or_edit.from_node <graphtage.Edit.from_node>`
    * If ``node_or_edit`` is a :class:`graphtage.TreeNode`:
        * If ``with_edits`` *and* the node is edited and has a non-zero cost,
            then choose :attr:`node_or_edit.edit <graphtage.EditedTreeNode.edit>`::

                node_or_edit.edit is not None and node_or_edit.edit.bounds().lower_bound > 0

        * Otherwise choose ``node_or_edit``
#. If the chosen object is an edit:
    * See if there is a specialized formatter for this edit by calling
      :meth:`graphtage.formatter.Formatter.get_formatter`
    * If so, delegate to that formatter and return.
    * If not, try calling the edit's :func:`graphtage.Edit.print` method. If :exc:`NotImplementedError` is
      *not* raised, return.
#. If the chosen object is a node, or if we failed to find a printer for the edit:
    * See if there is a specialized formatter for this node by calling
      :meth:`graphtage.formatter.Formatter.get_formatter`
    * If so, delegate to that formatter and return.
    * If not, print a debug warning and delegate to the node's internal print implementation
      :meth:`graphtage.TreeNode.print`.

This is implemented in :meth:`graphtage.GraphtageFormatter.print`. See the :ref:`Formatting Protocol` for how formatters
are chosen.