<!-- ##### SECTION Title ##### -->
GtkTreeModel

<!-- ##### SECTION Short_Description ##### -->
The tree interface used by GtkTreeView

<!-- ##### SECTION Long_Description ##### -->
<para>
The #GtkTreeModel interface defines a generic tree interface for use by
the #GtkTreeView widget.  It is an abstract interface, and is designed
to be usable with any appropriate data structure.  The programmer just
has to implement this interface on their own data type for it to be
viewable by a #GtkTreeView widget.
</para>

<para>
The model is represented as a hierarchical tree of strongly-typed,
columned data.  In other words, the model can be seen as a tree where
every node has different values depending on which column is being
queried.  The type of data found in a column is determined by using the
GType system (ie. #G_TYPE_INT, #GTK_TYPE_BUTTON, #G_TYPE_POINTER, etc.).
The types are homogeneous per column across all nodes.  It is important
to note that this interface only provides a way of examining a model and
observing changes.  The implementation of each individual model decides
how and if changes are made.
</para>

<para>
In order to make life simpler for programmers who do not need to write
their own specialized model, two generic models are provided &mdash; the
#GtkTreeStore and the #GtkListStore.  To use these, the developer simply
pushes data into these models as necessary.  These models provide the
data structure as well as all appropriate tree interfaces.  As a result,
implementing drag and drop, sorting, and storing data is trivial.  For
the vast majority of trees and lists, these two models are sufficient.
</para>

<para>
Models are accessed on a node/column level of granularity.  One can
query for the value of a model at a certain node and a certain column
on that node.  There are two structures used to reference a particular
node in a model.  They are the #GtkTreePath and the #GtkTreeIter
<footnote>
<para>
Here, <abbrev>iter</abbrev> is short for <quote>iterator</quote>
</para>
</footnote>
Most of the interface consists of operations on a #GtkTreeIter.
</para>

<para>
A path is essentially a potential node.  It is a location on a model
that may or may not actually correspond to a node on a specific model.
The #GtkTreePath struct can be converted into either an array of
unsigned integers or a string.  The string form is a list of numbers
separated by a colon.  Each number refers to the offset at that level.
Thus, the path <quote>0</quote> refers to the root node and the path
<quote>2:4</quote> refers to the fifth child of the third node.
</para>

<para>
By contrast, a #GtkTreeIter is a reference to a specific node on a
specific model.  It is a generic struct with an integer and three
generic pointers.  These are filled in by the model in a model-specific
way.  One can convert a path to an iterator by calling
gtk_tree_model_get_iter().  These iterators are the primary way of
accessing a model and are similar to the iterators used by
#GtkTextBuffer.  They are generally statically allocated on the stack and
only used for a short time.  The model interface defines a set of
operations using them for navigating the model.
</para>

<para>
It is expected that models fill in the iterator with private data.  For
example, the #GtkListStore model, which is internally a simple linked
list, stores a list node in one of the pointers.  The #GtkTreeModelSort
stores an array and an offset in two of the pointers.  Additionally,
there is an integer field.  This field is generally filled with a unique
stamp per model.  This stamp is for catching errors resulting from using
invalid iterators with a model.
</para>

<para>
The lifecycle of an iterator can be a little confusing at first.
Iterators are expected to always be valid for as long as the model is
unchanged (and doesn't emit a signal).  The model is considered to own
all outstanding iterators and nothing needs to be done to free them from
the user's point of view.  Additionally, some models guarantee that an
iterator is valid for as long as the node it refers to is valid (most
notably the #GtkTreeStore and #GtkListStore).  Although generally
uninteresting, as one always has to allow for the case where iterators
do not persist beyond a signal, some very important performance
enhancements were made in the sort model.  As a result, the
#GTK_TREE_MODEL_ITERS_PERSIST flag was added to indicate this behavior.
</para>

<para>
To help show some common operation of a model, some examples are
provided.  The first example shows three ways of getting the iter at the
location <quote>3:2:5</quote>.  While the first method shown is easier,
the second is much more common, as you often get paths from callbacks.
</para>
<para>
<example>
<title>Acquiring a <structname>GtkTreeIter</structname></title>
<programlisting>
/* Three ways of getting the iter pointing to the location
 */
{
  GtkTreePath *path;
  GtkTreeIter iter;
  GtkTreeIter parent_iter;

  /* get the iterator from a string */
  gtk_tree_model_get_iter_from_string (model, &amp;iter, "3:2:5");

  /* get the iterator from a path */
  path = gtk_tree_path_new_from_string ("3:2:5");
  gtk_tree_model_get_iter (model, &amp;iter, path);
  gtk_tree_path_free (path);


  /* walk the tree to find the iterator */
  gtk_tree_model_iter_nth_child (model, &amp;iter, NULL, 3);
  parent_iter = iter;
  gtk_tree_model_iter_nth_child (model, &amp;iter, &amp;parent_iter, 2);
  parent_iter = iter;
  gtk_tree_model_iter_nth_child (model, &amp;iter, &amp;parent_iter, 5);
}
</programlisting>
</example>
</para>

<para>
This second example shows a quick way of iterating through a list and
getting a string and an integer from each row.  The
<function>populate_model</function> function used below is not shown, as
it is specific to the #GtkListStore.  For information on how to write
such a function, see the #GtkListStore documentation.
<example>
<title>Reading data from a <structname>GtkTreeModel</structname></title>
<programlisting>
enum
{
  STRING_COLUMN,
  INT_COLUMN,
  N_COLUMNS
};

{
  GtkTreeModel *list_store;
  GtkTreeIter iter;
  gboolean valid;
  gint row_count = 0;

  /* make a new list_store */
  list_store = gtk_list_store_new (N_COLUMNS, G_TYPE_STRING, G_TYPE_INT);

  /* Fill the list store with data */
  populate_model (list_store);

  /* Get the first iter in the list */
  valid = gtk_tree_model_get_iter_first (list_store, &amp;iter);

  while (valid)
    {
      /* Walk through the list, reading each row */
      gchar *str_data;
      gint   int_data;

      /* Make sure you terminate calls to gtk_tree_model_get(<!-- -->)
       * with a '-1' value
       */
      gtk_tree_model_get (list_store, &amp;iter, 
                          STRING_COLUMN, &amp;str_data,
                          INT_COLUMN, &amp;int_data,
                          -1);

      /* Do something with the data */
      g_print ("Row &percnt;d: (&percnt;s,&percnt;d)\n", row_count, str_data, int_data);
      g_free (str_data);

      row_count ++;
      valid = gtk_tree_model_iter_next (list_store, &amp;iter);
    }
}
</programlisting>
</example>
</para>

<!-- ##### SECTION See_Also ##### -->
<para>
#GtkTreeView, #GtkTreeStore, #GtkListStore, <link linkend="gtk-GtkTreeView-drag-and-drop">GtkTreeDnd</link>, #GtkTreeSortable
</para>

<!-- ##### SECTION Stability_Level ##### -->


<!-- ##### SECTION Image ##### -->


<!-- ##### STRUCT GtkTreeModel ##### -->
<para>

</para>


<!-- ##### SIGNAL GtkTreeModel::row-changed ##### -->
<para>

</para>

@treemodel: the object which received the signal.
@arg1: 
@arg2: 

<!-- ##### SIGNAL GtkTreeModel::row-deleted ##### -->
<para>

</para>

@treemodel: the object which received the signal.
@arg1: 

<!-- ##### SIGNAL GtkTreeModel::row-has-child-toggled ##### -->
<para>

</para>

@treemodel: the object which received the signal.
@arg1: 
@arg2: 

<!-- ##### SIGNAL GtkTreeModel::row-inserted ##### -->
<para>

</para>

@treemodel: the object which received the signal.
@arg1: 
@arg2: 

<!-- ##### SIGNAL GtkTreeModel::rows-reordered ##### -->
<para>

</para>

@treemodel: the object which received the signal.
@arg1: 
@arg2: 
@arg3: 

<!-- ##### STRUCT GtkTreeIter ##### -->
<para>
The <structname>GtkTreeIter</structname> is the primary structure for
accessing a structure.  Models are expected to put a unique integer in
the <structfield>stamp</structfield> member, and put model-specific
data in the three <structfield>user_data</structfield> members.
</para>

@stamp: A unique stamp to catch invalid iterators
@user_data: Model specific data
@user_data2: Model specific data
@user_data3: Model specific data

<!-- ##### STRUCT GtkTreePath ##### -->
<para>

</para>


<!-- ##### STRUCT GtkTreeRowReference ##### -->
<para>

</para>


<!-- ##### STRUCT GtkTreeModelIface ##### -->
<para>

</para>

@g_iface: 
@row_changed: 
@row_inserted: 
@row_has_child_toggled: 
@row_deleted: 
@rows_reordered: 
@get_flags: 
@get_n_columns: 
@get_column_type: 
@get_iter: 
@get_path: 
@get_value: 
@iter_next: 
@iter_children: 
@iter_has_child: 
@iter_n_children: 
@iter_nth_child: 
@iter_parent: 
@ref_node: 
@unref_node: 

<!-- ##### USER_FUNCTION GtkTreeModelForeachFunc ##### -->
<para>

</para>

@model: The #GtkTreeModel currently being iterated
@path: The current #GtkTreePath
@iter: The current #GtkTreeIter
@data: The user data passed to gtk_tree_model_foreach()
@Returns: %TRUE to stop iterating, %FALSE to continue.


<!-- ##### ENUM GtkTreeModelFlags ##### -->
<para>
These flags indicate various properties of a #GtkTreeModel.  They are
returned by gtk_tree_model_get_flags(), and must be static for the
lifetime of the object.  A more complete description of
#GTK_TREE_MODEL_ITERS_PERSIST can be found in the overview of this
section.
</para>

@GTK_TREE_MODEL_ITERS_PERSIST: Iterators survive all signals emitted by the tree.
@GTK_TREE_MODEL_LIST_ONLY: The model is a list only, and never has children

<!-- ##### FUNCTION gtk_tree_path_new ##### -->
<para>

</para>

@void: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_new_from_string ##### -->
<para>

</para>

@path: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_new_from_indices ##### -->
<para>

</para>

@first_index: 
@Varargs: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_to_string ##### -->
<para>

</para>

@path: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_new_first ##### -->
<para>

</para>

@void: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_append_index ##### -->
<para>

</para>

@path: 
@index_: 


<!-- ##### FUNCTION gtk_tree_path_prepend_index ##### -->
<para>

</para>

@path: 
@index_: 


<!-- ##### FUNCTION gtk_tree_path_get_depth ##### -->
<para>

</para>

@path: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_get_indices ##### -->
<para>

</para>

@path: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_get_indices_with_depth ##### -->
<para>

</para>

@path: 
@depth: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_free ##### -->
<para>

</para>

@path: 


<!-- ##### FUNCTION gtk_tree_path_copy ##### -->
<para>

</para>

@path: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_compare ##### -->
<para>

</para>

@a: 
@b: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_next ##### -->
<para>

</para>

@path: 


<!-- ##### FUNCTION gtk_tree_path_prev ##### -->
<para>

</para>

@path: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_up ##### -->
<para>

</para>

@path: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_down ##### -->
<para>

</para>

@path: 


<!-- ##### FUNCTION gtk_tree_path_is_ancestor ##### -->
<para>

</para>

@path: 
@descendant: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_path_is_descendant ##### -->
<para>

</para>

@path: 
@ancestor: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_row_reference_new ##### -->
<para>

</para>

@model: 
@path: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_row_reference_new_proxy ##### -->
<para>

</para>

@proxy: 
@model: 
@path: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_row_reference_get_model ##### -->
<para>

</para>

@reference: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_row_reference_get_path ##### -->
<para>

</para>

@reference: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_row_reference_valid ##### -->
<para>

</para>

@reference: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_row_reference_free ##### -->
<para>

</para>

@reference: 


<!-- ##### FUNCTION gtk_tree_row_reference_copy ##### -->
<para>

</para>

@reference: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_row_reference_inserted ##### -->
<para>

</para>

@proxy: 
@path: 


<!-- ##### FUNCTION gtk_tree_row_reference_deleted ##### -->
<para>

</para>

@proxy: 
@path: 


<!-- ##### FUNCTION gtk_tree_row_reference_reordered ##### -->
<para>

</para>

@proxy: 
@path: 
@iter: 
@new_order: 


<!-- ##### FUNCTION gtk_tree_iter_copy ##### -->
<para>

</para>

@iter: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_iter_free ##### -->
<para>

</para>

@iter: 


<!-- ##### FUNCTION gtk_tree_model_get_flags ##### -->
<para>

</para>

@tree_model: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_get_n_columns ##### -->
<para>

</para>

@tree_model: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_get_column_type ##### -->
<para>

</para>

@tree_model: 
@index_: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_get_iter ##### -->
<para>

</para>

@tree_model: 
@iter: 
@path: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_get_iter_from_string ##### -->
<para>

</para>

@tree_model: 
@iter: 
@path_string: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_get_iter_first ##### -->
<para>

</para>

@tree_model: 
@iter: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_get_path ##### -->
<para>

</para>

@tree_model: 
@iter: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_get_value ##### -->
<para>

</para>

@tree_model: 
@iter: 
@column: 
@value: 


<!-- ##### FUNCTION gtk_tree_model_iter_next ##### -->
<para>

</para>

@tree_model: 
@iter: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_iter_children ##### -->
<para>

</para>

@tree_model: 
@iter: 
@parent: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_iter_has_child ##### -->
<para>

</para>

@tree_model: 
@iter: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_iter_n_children ##### -->
<para>

</para>

@tree_model: 
@iter: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_iter_nth_child ##### -->
<para>

</para>

@tree_model: 
@iter: 
@parent: 
@n: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_iter_parent ##### -->
<para>

</para>

@tree_model: 
@iter: 
@child: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_get_string_from_iter ##### -->
<para>

</para>

@tree_model: 
@iter: 
@Returns: 


<!-- ##### FUNCTION gtk_tree_model_ref_node ##### -->
<para>

</para>

@tree_model: 
@iter: 


<!-- ##### FUNCTION gtk_tree_model_unref_node ##### -->
<para>

</para>

@tree_model: 
@iter: 


<!-- ##### FUNCTION gtk_tree_model_get ##### -->
<para>

</para>

@tree_model: 
@iter: 
@Varargs: 


<!-- ##### FUNCTION gtk_tree_model_get_valist ##### -->
<para>

</para>

@tree_model: 
@iter: 
@var_args: 


<!-- ##### FUNCTION gtk_tree_model_foreach ##### -->
<para>

</para>

@model: 
@func: 
@user_data: 


<!-- ##### FUNCTION gtk_tree_model_row_changed ##### -->
<para>

</para>

@tree_model: 
@path: 
@iter: 


<!-- ##### FUNCTION gtk_tree_model_row_inserted ##### -->
<para>

</para>

@tree_model: 
@path: 
@iter: 


<!-- ##### FUNCTION gtk_tree_model_row_has_child_toggled ##### -->
<para>

</para>

@tree_model: 
@path: 
@iter: 


<!-- ##### FUNCTION gtk_tree_model_row_deleted ##### -->
<para>

</para>

@tree_model: 
@path: 


<!-- ##### FUNCTION gtk_tree_model_rows_reordered ##### -->
<para>

</para>

@tree_model: 
@path: 
@iter: 
@new_order: 


