Module: Gtk::TreeModel

Defined in:
(unknown)

Overview

The Gtk::TreeModel interface defines a generic tree interface for use by the Gtk::TreeView 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 Gtk::TreeView 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 Gtk::TreeStore 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 Gtk::TreePath-struct and the Gtk::TreeIter-struct (“iter” is short for iterator). Most of the interface consists of operations on a Gtk::TreeIter-struct.

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 Gtk::TreePath-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 ‘0` refers to the root node and the path `2:4` refers to the fifth child of the third node.

By contrast, a Gtk::TreeIter-struct 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 Gtk::TextBuffer. 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 Gtk::ListStore model, which is internally a simple linked list, stores a list node in one of the pointers. The Gtk::TreeModelSort 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 Gtk::TreeStore 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 Gtk::TreeIter-struct

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, check it is valid and walk
// through the list, reading each row.

valid = gtk_tree_model_get_iter_first (list_store,
                                       &iter);
while (valid)
 {
   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, &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 Gtk::TreeModel 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. Gtk::TreeView 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 Gtk::TreeModel, with child_model as the child_model and root as the virtual root.

Parameters:

  • root (Gtk::TreePath)

    A Gtk::TreePath or nil.

Returns:

#flagsGtk::TreeModelFlags

Returns a set of flags supported by this interface.

The flags are a bitwise combination of Gtk::TreeModelFlags. 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 Gtk::TreeModel

  • index_ (Integer)

    the column index

Returns:

#get_flags(tree_model) ⇒ Gtk::TreeModelFlags

Returns the flags supported by this interface.

Parameters:

Returns:

#get_iter(tree_model, iter, path) ⇒ TrueClass

Returns true, if iter was set.

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the uninitialized Gtk::TreeIter-struct

  • path (Gtk::TreePath)

    the Gtk::TreePath-struct

Returns:

  • (TrueClass)

    true, if iter was set

#get_iter_first(iter) ⇒ TrueClass

Initializes iter with the first iterator in the tree (the one at the path “0”) and returns true. Returns false if the tree is empty.

Parameters:

  • iter (Gtk::TreeIter)

    the uninitialized Gtk::TreeIter-struct

Returns:

  • (TrueClass)

    true, if iter was set

#get_iter_from_string(iter, path_string) ⇒ TrueClass

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 Gtk::TreeIter-struct

  • path_string (String)

    a string representation of a Gtk::TreePath-struct

Returns:

  • (TrueClass)

    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 Gtk::TreePath-struct.

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the Gtk::TreeIter-struct

Returns:

  • (Gtk::TreePath)

    a newly-created Gtk::TreePath-struct

#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 Gtk::TreeIter-struct

Returns:

  • (String)

    a newly-allocated string. Must be freed with g_free().

#get_valist(iter, var_args) ⇒ nil

See gtk_tree_model_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 Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the Gtk::TreeIter-struct

  • 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) ⇒ TrueClass

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

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the new Gtk::TreeIter-struct to be set to the child

  • parent (Gtk::TreeIter)

    the Gtk::TreeIter-struct, or nil

Returns:

  • (TrueClass)

    true, if iter has been set to the first child

#iter_has_child(tree_model, iter) ⇒ TrueClass

Returns true if iter has children.

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the Gtk::TreeIter-struct to test for children

Returns:

  • (TrueClass)

    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 Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the Gtk::TreeIter-struct, or nil

Returns:

  • (Integer)

    the number of children of iter

#iter_next(tree_model, iter) ⇒ TrueClass

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

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the Gtk::TreeIter-struct

Returns:

  • (TrueClass)

    true if iter has been changed to the next node

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

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

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the Gtk::TreeIter-struct to set to the nth child

  • parent (Gtk::TreeIter)

    the Gtk::TreeIter-struct to get the child from, or nil.

  • n (Integer)

    the index of the desired child

Returns:

  • (TrueClass)

    true, if parent has an n-th child

#iter_parent(tree_model, iter, child) ⇒ TrueClass

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

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the new Gtk::TreeIter-struct to set to the parent

  • child (Gtk::TreeIter)

    the Gtk::TreeIter-struct

Returns:

  • (TrueClass)

    true, if iter is set to the parent of child

#iter_previous(tree_model, iter) ⇒ TrueClass

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

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the Gtk::TreeIter-struct

Returns:

  • (TrueClass)

    true if iter has been changed to the previous node

#n_columnsInteger

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 Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the Gtk::TreeIter-struct

Returns:

  • (nil)

#row_changed(tree_model, path, iter) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • path (Gtk::TreePath)

    a Gtk::TreePath-struct pointing to the changed row

  • iter (Gtk::TreeIter)

    a valid Gtk::TreeIter-struct pointing to the changed row

Returns:

  • (nil)

#row_deleted(tree_model, path) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • path (Gtk::TreePath)

    a Gtk::TreePath-struct 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 Gtk::TreeModel

  • path (Gtk::TreePath)

    a Gtk::TreePath-struct pointing to the changed row

  • iter (Gtk::TreeIter)

    a valid Gtk::TreeIter-struct pointing to the changed row

Returns:

  • (nil)

#row_inserted(tree_model, path, iter) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • path (Gtk::TreePath)

    a Gtk::TreePath-struct pointing to the inserted row

  • iter (Gtk::TreeIter)

    a valid Gtk::TreeIter-struct pointing to the inserted row

Returns:

  • (nil)

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

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • path (Gtk::TreePath)

    a Gtk::TreePath-struct pointing to the tree node whose children have been reordered

  • iter (Gtk::TreeIter)

    a valid Gtk::TreeIter-struct 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` = oldpos`

Returns:

  • (nil)

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

Emits the Gtk::TreeModel::rows-reordered signal on tree_model.

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

Parameters:

  • path (Gtk::TreePath)

    a Gtk::TreePath-struct pointing to the tree node whose children have been reordered

  • iter (Gtk::TreeIter)

    a valid Gtk::TreeIter-struct 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` = oldpos`

  • length (Integer)

    length of new_order array

Returns:

  • (nil)

#unref_node(tree_model, iter) ⇒ nil

Parameters:

  • tree_model (Gtk::TreeModel)

    a Gtk::TreeModel

  • iter (Gtk::TreeIter)

    the Gtk::TreeIter-struct

Returns:

  • (nil)