Module: Gtk::TreeModel

Defined in:
(unknown)

Overview

The tree interface used by GtkTreeView

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.

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.

In order to make life simpler for programmers who do not need to
write their own specialized model, two generic models are provided
— 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.

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 [structGtk.TreePath] and
the [structGtk.TreeIter] (“iter” is short for iterator). Most of the
interface consists of operations on a [structGtk.TreeIter].

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. A [structGtk.TreePath] 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 0 refers to the root
node and the path 2:4 refers to the fifth child of
the third node.

By contrast, a [structGtk.TreeIter] 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.

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.

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.

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 3:2:5. While the first method shown is
easier, the second is much more common, as you often get paths from
callbacks.

Acquiring a GtkTreeIter

// 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,
                                     &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, &iter, path);
gtk_tree_path_free (path);

// walk the tree to find the iterator
gtk_tree_model_iter_nth_child (model, &iter,
                               NULL, 3);
parent_iter = iter;
gtk_tree_model_iter_nth_child (model, &iter,
                               &parent_iter, 2);
parent_iter = iter;
gtk_tree_model_iter_nth_child (model, &iter,
                               &parent_iter, 5);

This second example shows a quick way of iterating through a list
and getting a string and an integer from each row. The
populate_model() 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.

Reading data from a GtkTreeModel

enum
{
  STRING_COLUMN,
  INT_COLUMN,
  N_COLUMNS
};

...

GtkTreeModel *list_store;
GtkTreeIter iter;
gboolean valid;
int 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, check it is valid and walk
// through the list, reading each row.

valid = gtk_tree_model_get_iter_first (list_store,
                                       &iter);
while (valid)
 {
   char *str_data;
   int    int_data;

   // Make sure you terminate calls to gtk_tree_model_get() with a “-1” value
   gtk_tree_model_get (list_store, &iter,
                       STRING_COLUMN, &str_data,
                       INT_COLUMN, &int_data,
                       -1);

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

   valid = gtk_tree_model_iter_next (list_store,
                                     &iter);
   row_count++;
 }

The GtkTreeModel interface contains two methods for reference
counting: gtk_tree_model_ref_node() and gtk_tree_model_unref_node().
These two methods are optional to implement. The reference counting
is meant as a way for views to let models know when nodes are being
displayed. GtkTreeView will take a reference on a node when it is
visible, which means the node is either in the toplevel or expanded.
Being displayed does not mean that the node is currently directly
visible to the user in the viewport. Based on this reference counting
scheme a caching model, for example, can decide whether or not to cache
a node based on the reference count. A file-system based model would
not want to keep the entire file hierarchy in memory, but just the
folders that are currently expanded in every current view.

When working with reference counting, the following rules must be taken
into account:

  • Never take a reference on a node without owning a reference on its parent.
    This means that all parent nodes of a referenced node must be referenced
    as well.

  • Outstanding references on a deleted node are not released. This is not
    possible because the node has already been deleted by the time the
    row-deleted signal is received.

  • Models are not obligated to emit a signal on rows of which none of its
    siblings are referenced. To phrase this differently, signals are only
    required for levels in which nodes are referenced. For the root level
    however, signals must be emitted at all times (however the root level
    is always referenced when any view is attached).

Instance Method Summary collapse

Instance Method Details

#filter_new(root) ⇒ Gtk::TreeModel

Creates a new GtkTreeModel, with child_model as the child_model
and root as the virtual root.

Parameters:

  • root (Gtk::TreePath) —

    A GtkTreePath

Returns:

#flags ⇒ Gtk::TreeModelFlags

Returns a set of flags supported by this interface.

The flags are a bitwise combination of GtkTreeModelFlags.
The flags supported should not change during the lifetime
of the tree_model.

Returns:

#foreach(func, user_data) ⇒ nil

Calls func on each node in model in a depth-first fashion.

If func returns true, then the tree ceases to be walked,
and gtk_tree_model_foreach() returns.

Parameters:

  • func (Gtk::TreeModelForeachFunc) —

    a function to be called on each row

  • user_data (GObject) —

    user data to passed to func

Returns:

  • (nil)

#get(iter, array) ⇒ nil

Gets the value of one or more cells in the row referenced by iter.

The variable argument list should contain integer column numbers,
each column number followed by a place to store the value being
retrieved. The list is terminated by a -1. For example, to get a
value from column 0 with type %G_TYPE_STRING, you would
write: gtk_tree_model_get (model, iter, 0, &place_string_here, -1),
where place_string_here is a #gchararray
to be filled with the string.

Returned values with type %G_TYPE_OBJECT have to be unreferenced,
values with type %G_TYPE_STRING or %G_TYPE_BOXED have to be freed.
Other values are passed by value.

Parameters:

  • iter (Gtk::TreeIter) —

    a row in tree_model

  • array (Array) —

    pairs of column number and value return locations,
    terminated by -1

Returns:

  • (nil)

#get_column_type(tree_model, index_) ⇒ GLib::Type

Returns the type of the column.

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • index_ (Integer) —

    the column index

Returns:

  • (GLib::Type) —

    the type of the column

#get_flags(tree_model) ⇒ Gtk::TreeModelFlags

Returns the flags supported by this interface.

Parameters:

Returns:

#get_iter(tree_model, iter, path) ⇒ Boolean

Returns true, if iter was set.

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the uninitialized GtkTreeIter

  • path (Gtk::TreePath) —

    the GtkTreePath

Returns:

  • (Boolean) —

    true, if iter was set

#get_iter_first(iter) ⇒ Boolean

Initializes iter with the first iterator in the tree
(the one at the path "0").

Returns false if the tree is empty, true otherwise.

Parameters:

  • iter (Gtk::TreeIter) —

    the uninitialized GtkTreeIter

Returns:

  • (Boolean) —

    true, if iter was set

#get_iter_from_string(iter, path_string) ⇒ Boolean

Sets iter to a valid iterator pointing to path_string, if it
exists.

Otherwise, iter is left invalid and false is returned.

Parameters:

  • iter (Gtk::TreeIter) —

    an uninitialized GtkTreeIter

  • path_string (String) —

    a string representation of a GtkTreePath

Returns:

  • (Boolean) —

    true, if iter was set

#get_n_columns(tree_model) ⇒ Integer

Returns the number of columns.

Parameters:

Returns:

  • (Integer) —

    the number of columns

#get_path(tree_model, iter) ⇒ Gtk::TreePath

Returns a newly-created GtkTreePath.

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the GtkTreeIter

Returns:

  • (Gtk::TreePath) —

    a newly-created GtkTreePath

#get_string_from_iter(iter) ⇒ String

Generates a string representation of the iter.

This string is a “:” separated list of numbers.
For example, “4:10:0:3” would be an acceptable
return value for this string.

Parameters:

  • iter (Gtk::TreeIter) —

    a GtkTreeIter

Returns:

  • (String) —

    a newly-allocated string

#get_valist(iter, var_args) ⇒ nil

Gets the value of one or more cells in the row referenced by iter.

See [methodGtk.TreeModel.get], this version takes a va_list
for language bindings to use.

Parameters:

  • iter (Gtk::TreeIter) —

    a row in tree_model

  • var_args (Gtk::va_list) —

    va_list of column/return location pairs

Returns:

  • (nil)

#get_value(tree_model, iter, column, value) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the GtkTreeIter

  • column (Integer) —

    the column to lookup the value at

  • value (GObject::Value) —

    an empty GValue to set

Returns:

  • (nil)

#iter_children(tree_model, iter, parent) ⇒ Boolean

Returns true, if iter has been set to the first child.

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the new GtkTreeIter to be set to the child

  • parent (Gtk::TreeIter) —

    the GtkTreeIter

Returns:

  • (Boolean) —

    true, if iter has been set to the first child

#iter_has_child(tree_model, iter) ⇒ Boolean

Returns true if iter has children.

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the GtkTreeIter to test for children

Returns:

  • (Boolean) —

    true if iter has children

#iter_n_children(tree_model, iter) ⇒ Integer

Returns the number of children of iter.

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the GtkTreeIter

Returns:

  • (Integer) —

    the number of children of iter

#iter_next(tree_model, iter) ⇒ Boolean

Returns true if iter has been changed to the next node.

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the GtkTreeIter

Returns:

  • (Boolean) —

    true if iter has been changed to the next node

#iter_nth_child(tree_model, iter, parent, n) ⇒ Boolean

Returns true, if parent has an n-th child.

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the GtkTreeIter to set to the nth child

  • parent (Gtk::TreeIter) —

    the GtkTreeIter to get the child from

  • n (Integer) —

    the index of the desired child

Returns:

  • (Boolean) —

    true, if parent has an n-th child

#iter_parent(tree_model, iter, child) ⇒ Boolean

Returns true, if iter is set to the parent of child.

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the new GtkTreeIter to set to the parent

  • child (Gtk::TreeIter) —

    the GtkTreeIter

Returns:

  • (Boolean) —

    true, if iter is set to the parent of child

#iter_previous(tree_model, iter) ⇒ Boolean

Returns true if iter has been changed to the previous node.

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the GtkTreeIter

Returns:

  • (Boolean) —

    true if iter has been changed to the previous node

#n_columns ⇒ Integer

Returns the number of columns supported by tree_model.

Returns:

  • (Integer) —

    the number of columns

#ref_node(tree_model, iter) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the GtkTreeIter

Returns:

  • (nil)

#row_changed(tree_model, path, iter) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • path (Gtk::TreePath) —

    a GtkTreePath pointing to the changed row

  • iter (Gtk::TreeIter) —

    a valid GtkTreeIter pointing to the changed row

Returns:

  • (nil)

#row_deleted(tree_model, path) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • path (Gtk::TreePath) —

    a GtkTreePath pointing to the previous location of
    the deleted row

Returns:

  • (nil)

#row_has_child_toggled(tree_model, path, iter) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • path (Gtk::TreePath) —

    a GtkTreePath pointing to the changed row

  • iter (Gtk::TreeIter) —

    a valid GtkTreeIter pointing to the changed row

Returns:

  • (nil)

#row_inserted(tree_model, path, iter) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • path (Gtk::TreePath) —

    a GtkTreePath pointing to the inserted row

  • iter (Gtk::TreeIter) —

    a valid GtkTreeIter pointing to the inserted row

Returns:

  • (nil)

#rows_reordered(tree_model, path, iter, new_order) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • path (Gtk::TreePath) —

    a GtkTreePath pointing to the tree node whose children
    have been reordered

  • iter (Gtk::TreeIter) —

    a valid GtkTreeIter pointing to the node whose children
    have been reordered, or nil if the depth of path is 0

  • new_order (Integer) —

    an array of integers mapping the current position of
    each child to its old position before the re-ordering,
    i.e. new_order[newpos] = oldpos

Returns:

  • (nil)

#rows_reordered_with_length(path, iter, new_order, length) ⇒ nil

Emits the ::rows-reordered signal on tree_model.

See [signalGtk.TreeModel::rows-reordered].

This should be called by models when their rows have been
reordered.

Parameters:

  • path (Gtk::TreePath) —

    a GtkTreePath pointing to the tree node whose children
    have been reordered

  • iter (Gtk::TreeIter) —

    a valid GtkTreeIter pointing to the node
    whose children have been reordered, or nil if the depth
    of path is 0

  • new_order (Array<Integer>) —

    an array of integers
    mapping the current position of each child to its old
    position before the re-ordering,
    i.e. new_order[newpos] = oldpos

  • length (Integer) —

    length of new_order array

Returns:

  • (nil)

#unref_node(tree_model, iter) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel) —

    a GtkTreeModel

  • iter (Gtk::TreeIter) —

    the GtkTreeIter

Returns:

  • (nil)