migrating-gtkiconview.sgml

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<chapter id="gtk-migrating-GtkIconView">

  <title>Migrating from GnomeIconList to GtkIconView</title>

  <para>
    Since version 2.6, GTK+ provides the <link 
    linkend="GtkIconView">GtkIconView</link>
    widget. It is similar in functionality to the 
    <structname>GnomeIconList</structname> widget in the 
    libgnomeui library, both widgets provide a way to lay out named icons in 
    a grid. The distinctive feature of the GTK+ widget is that it follows the 
    model-view pattern, allowing it to share the actual data (i.e. the names 
    and images of the icons) with other views.
  </para>

  <para>
    <link linkend="GtkIconView">GtkIconView</link> currently doesn't support 
    some features found in <structname>GnomeIconList</structname>. Icons can 
    not be positioned freely, the spacing is not customizable, and it is not 
    possible to edit the names of icons. 
  </para>

  <para>
    To convert an application that uses <structname>GnomeIconList</structname> 
    to <link linkend="GtkIconView">GtkIconView</link>, the first step is to 
    organize your data in a <link linkend="GtkTreeModel">GtkTreeModel</link>. 
    <structname>GnomeIconList</structname> lets you directly insert data with 
    <function>gnome_icon_list_insert()</function> and 
    <function>gnome_icon_list_insert_pixbuf()</function> and their
    append variants. So, if you previously had a function to fill your icon 
    list similar to this one:
    <informalexample><programlisting>
      void 
      fill_icon_list (GnomeIconList *icon_list)
      {
        gnome_icon_list_append (icon_list, "file1.png", "Icon 1");
        gnome_icon_list_append (icon_list, "file2.png", "Icon 2");

        /* more icons ... */ 
      }
    </programlisting></informalexample>
    you will have to create a tree model, attach your icon view to it, and 
    fill the model:
    <informalexample><programlisting>
      enum { 
        PIXBUF_COLUMN,
        TEXT_COLUMN,

        /* you can have more columns here, e.g */ 

        DATA_COLUMN
      };
 
      void 
      fill_model (GtkListStore *model)
      {
        GtkTreeIter iter;
        GdkPixbuf *pixbuf;

        gtk_list_store_append (model, &amp;iter);
        pixbuf = gdk_pixbuf_new_from_file ("file1.png", NULL);
        gtk_list_store_set (model, &amp;iter, PIXBUF_COLUMN, pixbuf, TEXT_COLUMN, "Icon 1", -1);
        g_object_unref (pixbuf);

        gtk_list_store_append (model, &amp;iter);
        pixbuf = gdk_pixbuf_new_from_file ("file2.png", NULL);
        gnome_icon_list_append (icon_list, PIXBUF_COLUMN, pixbuf, TEXT_COLUMN, "Icon 2", -1);
        g_object_unref (pixbuf);

        /* more icons ... */ 
      }

      int 
      main (int argc, char *argv[])
      {
        GtkWidget *icon_view;
        GtkTreeModel *model;

        gtk_init (&amp;argc, &amp;argv);

        /* do other initialization... */

        /* construct the GtkIconView */
        icon_view = gtk_icon_view_new ();
        model = gtk_list_store_new (3, GDK_TYPE_PIXBUF, G_TYPE_STRING, G_TYPE_POINTER);

        gtk_icon_view_set_pixbuf_column (GTK_ICON_VIEW (icon_view), PIXBUF_COLUMN);
        gtk_icon_view_set_text_column (GTK_ICON_VIEW (icon_view), TEXT_COLUMN);
        gtk_icon_view_set_model GTK_ICON_VIEW (icon_view), model);

        fill_model (model);

        /* ... */
      }
    </programlisting></informalexample>
    This example uses a <link linkend="GtkListStore">GtkListStore</link> as
    model, but part of the elegance of the model-view pattern is that you can 
    easily use another tree model implementation, or even write your own 
    custom tree model.
  </para>

  <para>
    Your application may make use of extra data attached to the icons in the 
    <structname>GnomeIconList</structname> via 
    <function>gnome_icon_list_set_icon_data()</function> and 
    <function>gnome_icon_list_get_icon_data()</function>. With 
    <link linkend="GtkIconView">GtkIconView</link> such data is most 
    conveniently stored in an extra column in the tree model, so you would 
    call a function like
    <informalexample><programlisting>
    void 
    set_icon_data (GtkIconView *icon_view,
                   gint         idx,
                   gpointer     data)
    {
       GtkTreeModel *model;
       GtkTreeIter iter;

       model = gtk_icon_view_get_model (icon_view);
    
       if (gtk_tree_model_iter_nth_child (model, &amp;iter, NULL, idx))
         gtk_list_store_set (GTK_LIST_STORE (model), &amp;iter, 
                             DATA_COLUMN, data, -1);
    }
    </programlisting></informalexample>
    assuming that your tree model has a <literal>DATA_COLUMN</literal> of type 
    <literal>G_TYPE_POINTER</literal>.
  </para>

  <para>
    There is a number of minor API differences between 
    <structname>GnomeIconList</structname> and 
    <structname>GtkIconView</structname>:
    <itemizedlist> 
     <listitem><para>
       <typename>GnomeIconListMode</typename> is replaced by the 
       <link linkend="GtkIconView--orientation">orientation</link> 
       property of <structname>GtkIconView</structname>
     </para></listitem>
     <listitem><para>
       <structname>GtkIconView</structname> can not be frozen in the same 
       way as <structname>GnomeIconList</structname> can with 
       <function>gnome_icon_list_freeze()</function> and 
       <function>gnome_icon_list_thaw()</function>. Instead you can 
       replace the whole model of a <structname>GtkIconView</structname>, 
       instead of doing many small changes to the existing model.
     </para></listitem>
    </itemizedlist>
  </para> 
</chapter>

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