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<chapter id="gtk-migrating-GtkComboBox">
<title>Migrating from GtkOptionMenu and GtkCombo to GtkComboBox and GtkComboBoxEntry</title>
<para>
Prior to 2.4, GTK+ offered two widgets for the task of selecting one
item from a list of options.
<link linkend="GtkOptionMenu">GtkOptionMenu</link> presents the list of
options as a menu while <link linkend="GtkCombo">GtkCombo</link> presents
them in a Windows-style list popup. The only difference between the two
is that a <link linkend="GtkCombo">GtkCombo</link> allows to manually
edit the selected value, while the
<link linkend="GtkOptionMenu">GtkOptionMenu</link> does not.
</para>
<para>
In GTK+ 2.4, a unified API for list selection was introduced, with
<link linkend="GtkComboBox">GtkComboBox</link> for the non-editable case
and <link linkend="GtkComboBoxEntry">GtkComboBoxEntry</link> for the
editable case.
The selection of the display style — menu or list —
is no longer done at the API level, but has been made themeable via
the style property
<link linkend="GtkComboBox--appearance">GtkComboBox::appearance</link>.
</para>
<section id="migrating-GtkOptionMenu">
<title>Migrating from GtkOptionMenu to GtkComboBox</title>
<para>
Here is an example of a simple, but typical use of
<link linkend="GtkOptionMenu">GtkOptionMenu</link>:
<informalexample><programlisting>
GtkWidget *option_menu, *menu, *menu_item;
option_menu = gtk_option_menu_new ();
menu = gtk_menu_new ();
menu_item = gtk_menu_item_new_with_label ("First Item");
gtk_menu_shell_append (GTK_MENU_SHELL (menu), menu_item);
gtk_widget_show (menu_item);
menu_item = gtk_menu_item_new_with_label ("Second Item");
gtk_menu_shell_append (GTK_MENU_SHELL (menu), menu_item);
gtk_widget_show (menu_item);
menu_item = gtk_menu_item_new_with_label ("Third Item");
gtk_menu_shell_append (GTK_MENU_SHELL (menu), menu_item);
gtk_widget_show (menu_item);
gtk_option_menu_set_menu (GTK_OPTION_MENU (option_menu), menu);
</programlisting></informalexample>
In order to react to the user's selection, connect to the "changed"
signal on the option menu and use <link linkend="gtk-option-menu-get-history"><function>gtk_option_menu_get_history()</function></link>
to retrieve the index of the selected item.
</para>
<para>
And here is how it would be done with a
<link linkend="GtkComboBox">GtkComboBox</link>:
<informalexample><programlisting>
GtkWidget *combo_box;
combo_box = gtk_combo_box_new_text ();
gtk_combo_box_append_text (GTK_COMBO_BOX (combo_box), "First Item");
gtk_combo_box_append_text (GTK_COMBO_BOX (combo_box), "Second Item");
gtk_combo_box_append_text (GTK_COMBO_BOX (combo_box), "Third Item");
</programlisting></informalexample>
In order to react to the user's selection, connect to the "changed"
signal on the combo box and use <link linkend="gtk-combo-box-get-active"><function>gtk_combo_box_get_active()</function></link>
to retrieve the index of the selected item.
</para>
<para>
A slightly more complex example involving images:
<informalexample><programlisting>
GtkWidget *option_menu, *menu, *menu_item;
option_menu = gtk_option_menu_new ();
menu = gtk_menu_new ();
menu_item = gtk_image_menu_item_new_with_label ("First Item");
gtk_image_menu_item_set_image (gtk_image_new_from_pixbuf (pixbuf1));
gtk_menu_shell_append (GTK_MENU_SHELL (menu), menu_item);
gtk_widget_show (menu_item);
menu_item = gtk_image_menu_item_new_with_label ("Second Item");
gtk_image_menu_item_set_image (gtk_image_new_from_pixbuf (pixbuf2));
gtk_menu_shell_append (GTK_MENU_SHELL (menu), menu_item);
gtk_widget_show (menu_item);
menu_item = gtk_image_menu_item_new_with_label ("Third Item");
gtk_image_menu_item_set_image (gtk_image_new_from_pixbuf (pixbuf3));
gtk_menu_shell_append (GTK_MENU_SHELL (menu), menu_item);
gtk_widget_show (menu_item);
gtk_option_menu_set_menu (GTK_OPTION_MENU (option_menu), menu);
</programlisting></informalexample>
</para>
<para>
can be done using a <link linkend="GtkComboBox">GtkComboBox</link>
as follows:
<informalexample><programlisting>
GtkListStore *store;
GtkTreeIter iter;
GtkCellRenderer *renderer;
GtkWidget *combo_box;
store = gtk_list_store_new (2, GDK_TYPE_PIXBUF, G_TYPE_STRING);
gtk_list_store_append (store, &iter);
gtk_list_store_set (store, &iter, 0, pixbuf1, 1, "First Item", -1);
gtk_list_store_append (store, &iter);
gtk_list_store_set (store, &iter, 0, pixbuf2, 1, "Second Item", -1);
gtk_list_store_append (store, &iter);
gtk_list_store_set (store, &iter, 0, pixbuf3, 1, "Third Item", -1);
combo_box = gtk_combo_box_new_with_model (GTK_TREE_MODEL (store));
renderer = gtk_cell_renderer_pixbuf_new ();
gtk_cell_layout_pack_start (GTK_CELL_LAYOUT (combo_box), renderer, FALSE);
gtk_cell_layout_set_attributes (GTK_CELL_LAYOUT (combo_box), renderer,
"pixbuf", 0,
NULL);
renderer = gtk_cell_renderer_text_new ();
gtk_cell_layout_pack_start (GTK_CELL_LAYOUT (combo_box), renderer, TRUE);
gtk_cell_layout_set_attributes (GTK_CELL_LAYOUT (combo_box), renderer,
"text", 1,
NULL);
</programlisting></informalexample>
</para>
</section>
<section id="migrating-GtkCombo">
<title>Migrating from GtkCombo to GtkComboBoxEntry</title>
<para>
Here is an example of a simple, but typical use of a
<link linkend="GtkCombo">GtkCombo</link>:
<informalexample><programlisting>
GtkWidget *combo;
GList *items = NULL;
items = g_list_append (items, "First Item");
items = g_list_append (items, "Second Item");
items = g_list_append (items, "Third Item");
combo = gtk_combo_new ();
gtk_combo_set_popdown_strings (GTK_COMBO (combo), items);
</programlisting></informalexample>
In order to react to the user's selection, connect to the "changed"
signal on the combo and use
<literal>gtk_entry_get_text (GTK_ENTRY (combo->entry))</literal>
to retrieve the selected text.
</para>
<para>
And here is how it would be done using <link linkend="GtkComboBoxEntry">GtkComboBoxEntry</link>:
<informalexample><programlisting>
combo_box = gtk_combo_box_entry_new_text ();
gtk_combo_box_append_text (GTK_COMBO_BOX (combo_box), "First Item");
gtk_combo_box_append_text (GTK_COMBO_BOX (combo_box), "Second Item");
gtk_combo_box_append_text (GTK_COMBO_BOX (combo_box), "Third Item");
</programlisting></informalexample>
In order to react to the user's selection, connect to the "changed"
signal on the combo and use
<literal>gtk_entry_get_text (GTK_ENTRY (GTK_BIN (combo_box)->child))</literal>
to retrieve the selected text.
</para>
</section>
<section id="new-features-GtkComboBox">
<title>New features</title>
<para>
The new widgets have more to offer than a mere combination of the
features of <link linkend="GtkOptionMenu">GtkOptionMenu</link> and
<link linkend="GtkCombo">GtkCombo</link>. Notable new features
include:
<variablelist>
<varlistentry>
<term>Grid mode</term>
<listitem><para>Sometimes it is preferable to display the available
options not in a linear list, but in a grid. A typical example
would be a "color combo" where the individual items are small
square color swatches. The new widgets support gridded display
with the functions
<link linkend="gtk-combo-box-set-wrap-width"><function>gtk_combo_box_set_wrap_width()</function></link>,
<link linkend="gtk-combo-box-set-row-span-column"><function>gtk_combo_box_set_row_span_column()</function></link> and
<link linkend ="gtk-combo-box-set-column-span-column"><function>gtk_combo_box_set_column_span_column()</function></link>.
</para></listitem>
</varlistentry>
<varlistentry>
<term>Display of icons</term>
<listitem><para>An often-heard complaint about
<link linkend="GtkOptionMenu">GtkOptionMenu</link> is that the
icons which appear in the image menu items in its menu are not
displayed in the button showing the selected item. This limitation
has been removed in <link linkend="GtkComboBox">GtkComboBox</link>;
the selected item appears in the same way as the options in
the popup.
</para></listitem>
</varlistentry>
<varlistentry>
<term>Full tree model power</term>
<listitem><para>
Since the new widgets are built around the same models that are
used for <link linkend="GtkTreeView">GtkTreeView</link>, all of
the powerful machinery of tree models and cell renderers can be
used.
</para></listitem>
</varlistentry>
</variablelist>
</para>
</section>
</chapter>
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