+/**
+ * SECTION:gtkfilechooser
+ * @Short_description: File chooser interface used by GtkFileChooserWidget and GtkFileChooserDialog
+ * @Title: GtkFileChooser
+ * @See_also: #GtkFileChooserDialog, #GtkFileChooserWidget, #GtkFileChooserButton
+ *
+ * #GtkFileChooser is an interface that can be implemented by file
+ * selection widgets. In GTK+, the main objects that implement this
+ * interface are #GtkFileChooserWidget, #GtkFileChooserDialog, and
+ * #GtkFileChooserButton. You do not need to write an object that
+ * implements the #GtkFileChooser interface unless you are trying to
+ * adapt an existing file selector to expose a standard programming
+ * interface.
+ *
+ * #GtkFileChooser allows for shortcuts to various places in the filesystem.
+ * In the default implementation these are displayed in the left pane. It
+ * may be a bit confusing at first that these shortcuts come from various
+ * sources and in various flavours, so lets explain the terminology here:
+ * <variablelist>
+ * <varlistentry>
+ * <term>Bookmarks</term>
+ * <listitem>
+ * are created by the user, by dragging folders from the
+ * right pane to the left pane, or by using the "Add". Bookmarks
+ * can be renamed and deleted by the user.
+ * </listitem>
+ * </varlistentry>
+ * <varlistentry>
+ * <term>Shortcuts</term>
+ * <listitem>
+ * can be provided by the application or by the underlying filesystem
+ * abstraction (e.g. both the gnome-vfs and the Windows filesystems
+ * provide "Desktop" shortcuts). Shortcuts cannot be modified by the
+ * user.
+ * </listitem>
+ * </varlistentry>
+ * <varlistentry>
+ * <term>Volumes</term>
+ * <listitem>
+ * are provided by the underlying filesystem abstraction. They are
+ * the "roots" of the filesystem.
+ * </listitem>
+ * </varlistentry>
+ * </variablelist>
+ *
+ * <refsect2 id="gtkfilechooser-encodings">
+ * <title>File Names and Encodings</title>
+ * When the user is finished selecting files in a
+ * #GtkFileChooser, your program can get the selected names
+ * either as filenames or as URIs. For URIs, the normal escaping
+ * rules are applied if the URI contains non-ASCII characters.
+ * However, filenames are <emphasis>always</emphasis> returned in
+ * the character set specified by the
+ * <envar>G_FILENAME_ENCODING</envar> environment variable.
+ * Please see the GLib documentation for more details about this
+ * variable.
+ * <note>
+ * This means that while you can pass the result of
+ * gtk_file_chooser_get_filename() to
+ * <function>open(2)</function> or
+ * <function>fopen(3)</function>, you may not be able to
+ * directly set it as the text of a #GtkLabel widget unless you
+ * convert it first to UTF-8, which all GTK+ widgets expect.
+ * You should use g_filename_to_utf8() to convert filenames
+ * into strings that can be passed to GTK+ widgets.
+ * </note>
+ * </refsect2>
+ * <refsect2 id="gtkfilechooser-preview">
+ * <title>Adding a Preview Widget</title>
+ * <para>
+ * You can add a custom preview widget to a file chooser and then
+ * get notification about when the preview needs to be updated.
+ * To install a preview widget, use
+ * gtk_file_chooser_set_preview_widget(). Then, connect to the
+ * #GtkFileChooser::update-preview signal to get notified when
+ * you need to update the contents of the preview.
+ * </para>
+ * <para>
+ * Your callback should use
+ * gtk_file_chooser_get_preview_filename() to see what needs
+ * previewing. Once you have generated the preview for the
+ * corresponding file, you must call
+ * gtk_file_chooser_set_preview_widget_active() with a boolean
+ * flag that indicates whether your callback could successfully
+ * generate a preview.
+ * </para>
+ * <example id="example-gtkfilechooser-preview">
+ * <title>Sample Usage</title>
+ * <programlisting>
+ * {
+ * GtkImage *preview;
+ *
+ * ...
+ *
+ * preview = gtk_image_new (<!-- -->);
+ *
+ * gtk_file_chooser_set_preview_widget (my_file_chooser, preview);
+ * g_signal_connect (my_file_chooser, "update-preview",
+ * G_CALLBACK (update_preview_cb), preview);
+ * }
+ *
+ * static void
+ * update_preview_cb (GtkFileChooser *file_chooser, gpointer data)
+ * {
+ * GtkWidget *preview;
+ * char *filename;
+ * GdkPixbuf *pixbuf;
+ * gboolean have_preview;
+ *
+ * preview = GTK_WIDGET (data);
+ * filename = gtk_file_chooser_get_preview_filename (file_chooser);
+ *
+ * pixbuf = gdk_pixbuf_new_from_file_at_size (filename, 128, 128, NULL);
+ * have_preview = (pixbuf != NULL);
+ * g_free (filename);
+ *
+ * gtk_image_set_from_pixbuf (GTK_IMAGE (preview), pixbuf);
+ * if (pixbuf)
+ * g_object_unref (pixbuf);
+ *
+ * gtk_file_chooser_set_preview_widget_active (file_chooser, have_preview);
+ * }
+ * </programlisting>
+ * </example>
+ * </refsect2>
+ * <refsect2 id="gtkfilechooser-extra">
+ * <title>Adding Extra Widgets</title>
+ * <para>
+ * You can add extra widgets to a file chooser to provide options
+ * that are not present in the default design. For example, you
+ * can add a toggle button to give the user the option to open a
+ * file in read-only mode. You can use
+ * gtk_file_chooser_set_extra_widget() to insert additional
+ * widgets in a file chooser.
+ * </para>
+ * <example id="example-gtkfilechooser-extra">
+ * <title>Sample Usage</title>
+ * <programlisting>
+ *
+ * GtkWidget *toggle;
+ *
+ * ...
+ *
+ * toggle = gtk_check_button_new_with_label ("Open file read-only");
+ * gtk_widget_show (toggle);
+ * gtk_file_chooser_set_extra_widget (my_file_chooser, toggle);
+ * }
+ * </programlisting>
+ * </example>
+ * <note>
+ * If you want to set more than one extra widget in the file
+ * chooser, you can a container such as a #GtkBox or a #GtkGrid
+ * and include your widgets in it. Then, set the container as
+ * the whole extra widget.
+ * </note>
+ * </refsect2>
+ * <refsect2 id="gtkfilechooser-key-bindings">
+ * <title>Key Bindings</title>
+ * <para>
+ * Internally, GTK+ implements a file chooser's graphical user
+ * interface with the private
+ * <classname>GtkFileChooserDefaultClass</classname>. This
+ * widget has several <link linkend="gtk-Bindings">key
+ * bindings</link> and their associated signals. This section
+ * describes the available key binding signals.
+ * </para>
+ * <example id="gtkfilechooser-key-binding-example">
+ * <title>GtkFileChooser key binding example</title>
+ * <para>
+ * The default keys that activate the key-binding signals in
+ * <classname>GtkFileChooserDefaultClass</classname> are as
+ * follows:
+ * </para>
+ * <informaltable>
+ * <tgroup cols="2">
+ * <tbody>
+ * <row>
+ * <entry>Signal name</entry>
+ * <entry>Default key combinations</entry>
+ * </row>
+ * <row>
+ * <entry>location-popup</entry>
+ * <entry>
+ * <keycombo><keycap>Control</keycap><keycap>L</keycap></keycombo> (empty path);
+ * <keycap>/</keycap> (path of "/")
+ * <footnote>
+ * Both the individual <keycap>/</keycap> key and the
+ * numeric keypad's "divide" key are supported.
+ * </footnote>;
+ * <keycap>~</keycap> (path of "~")
+ * </entry>
+ * </row>
+ * <row>
+ * <entry>up-folder</entry>
+ * <entry>
+ * <keycombo><keycap>Alt</keycap><keycap>Up</keycap></keycombo>;
+ * <keycombo><keycap>Alt</keycap><keycap>Shift</keycap><keycap>Up</keycap></keycombo>
+ * <footnote>
+ * Both the individual Up key and the numeric
+ * keypad's Up key are supported.
+ * </footnote>;
+ * <keycap>Backspace</keycap>
+ * </entry>
+ * </row>
+ * <row>
+ * <entry>down-folder</entry>
+ * <entry>
+ * <keycombo><keycap>Alt</keycap><keycap>Down</keycap></keycombo>;
+ * <keycombo><keycap>Alt</keycap><keycap>Shift</keycap><keycap>Down</keycap></keycombo>
+ * <footnote>
+ * Both the individual Down key and the numeric
+ * keypad's Down key are supported.
+ * </footnote>
+ * </entry>
+ * </row>
+ * <row>
+ * <entry>home-folder</entry>
+ * <entry><keycombo><keycap>Alt</keycap><keycap>Home</keycap></keycombo></entry>
+ * </row>
+ * <row>
+ * <entry>desktop-folder</entry>
+ * <entry><keycombo><keycap>Alt</keycap><keycap>D</keycap></keycombo></entry>
+ * </row>
+ * <row>
+ * <entry>quick-bookmark</entry>
+ * <entry><keycombo><keycap>Alt</keycap><keycap>1</keycap></keycombo> through <keycombo><keycap>Alt</keycap><keycap>0</keycap></keycombo></entry>
+ * </row>
+ * </tbody>
+ * </tgroup>
+ * </informaltable>
+ * <para>
+ * You can change these defaults to something else. For
+ * example, to add a <keycap>Shift</keycap> modifier to a few
+ * of the default bindings, you can include the following
+ * fragment in your <filename>.config/gtk-3.0/gtk.css</filename> file:
+ * </para>
+ * <programlisting>
+ * @binding-set MyOwnFilechooserBindings
+ * {
+ * bind "<Alt><Shift>Up" { "up-folder" () }
+ * bind "<Alt><Shift>Down" { "down-folder" () }
+ * bind "<Alt><Shift>Home" { "home-folder" () }
+ * }
+ *
+ * GtkFileChooserDefault
+ * {
+ * gtk-key-bindings: MyOwnFilechooserBindings
+ * }
+ * </programlisting>
+ * </example>
+ * <refsect3 id="GtkFileChooserDefault-location-popup">
+ * <title>The "GtkFileChooserDefault::location-popup" signal</title>
+ * <programlisting>
+ * void user_function (GtkFileChooserDefault *chooser,
+ * const char *path,
+ * <link linkend="gpointer">gpointer</link> user_data);
+ * </programlisting>
+ * <para>
+ * This is used to make the file chooser show a "Location"
+ * dialog which the user can use to manually type the name of
+ * the file he wishes to select. The
+ * <parameter>path</parameter> argument is a string that gets
+ * put in the text entry for the file name. By default this is bound to
+ * <keycombo><keycap>Control</keycap><keycap>L</keycap></keycombo>
+ * with a <parameter>path</parameter> string of "" (the empty
+ * string). It is also bound to <keycap>/</keycap> with a
+ * <parameter>path</parameter> string of "<literal>/</literal>"
+ * (a slash): this lets you type <keycap>/</keycap> and
+ * immediately type a path name. On Unix systems, this is bound to
+ * <keycap>~</keycap> (tilde) with a <parameter>path</parameter> string
+ * of "~" itself for access to home directories.
+ * </para>
+ * <variablelist role="params">
+ * <varlistentry>
+ * <term><parameter>chooser</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * the object which received the signal.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * <varlistentry>
+ * <term><parameter>path</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * default contents for the text entry for the file name
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * <varlistentry>
+ * <term><parameter>user_data</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * user data set when the signal handler was connected.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * </variablelist>
+ * <note>
+ * You can create your own bindings for the
+ * #GtkFileChooserDefault::location-popup signal with custom
+ * <parameter>path</parameter> strings, and have a crude form
+ * of easily-to-type bookmarks. For example, say you access
+ * the path <filename>/home/username/misc</filename> very
+ * frequently. You could then create an <keycombo>
+ * <keycap>Alt</keycap> <keycap>M</keycap> </keycombo>
+ * shortcut by including the following in your
+ * <filename>.config/gtk-3.0/gtk.css</filename>:
+ * <programlisting>
+ * @binding-set MiscShortcut
+ * {
+ * bind "<Alt>M" { "location-popup" ("/home/username/misc") }
+ * }
+ *
+ * GtkFileChooserDefault
+ * {
+ * gtk-key-bindings: MiscShortcut
+ * }
+ * </programlisting>
+ * </note>
+ * </refsect3>
+ * <refsect3 id="GtkFileChooserDefault-up-folder">
+ * <title>The "GtkFileChooserDefault::up-folder" signal</title>
+ * <programlisting>
+ * void user_function (GtkFileChooserDefault *chooser,
+ * <link linkend="gpointer">gpointer</link> user_data);
+ * </programlisting>
+ * <para>
+ * This is used to make the file chooser go to the parent of
+ * the current folder in the file hierarchy. By default this
+ * is bound to <keycap>Backspace</keycap> and
+ * <keycombo><keycap>Alt</keycap><keycap>Up</keycap></keycombo>
+ * (the Up key in the numeric keypad also works).
+ * </para>
+ * <variablelist role="params">
+ * <varlistentry>
+ * <term><parameter>chooser</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * the object which received the signal.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * <varlistentry>
+ * <term><parameter>user_data</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * user data set when the signal handler was connected.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * </variablelist>
+ * </refsect3>
+ * <refsect3 id="GtkFileChooserDefault-down-folder">
+ * <title>The "GtkFileChooserDefault::down-folder" signal</title>
+ * <programlisting>
+ * void user_function (GtkFileChooserDefault *chooser,
+ * <link linkend="gpointer">gpointer</link> user_data);
+ * </programlisting>
+ * <para>
+ * This is used to make the file chooser go to a child of the
+ * current folder in the file hierarchy. The subfolder that
+ * will be used is displayed in the path bar widget of the file
+ * chooser. For example, if the path bar is showing
+ * "/foo/<emphasis>bar/</emphasis>baz", then this will cause
+ * the file chooser to switch to the "baz" subfolder. By
+ * default this is bound to
+ * <keycombo><keycap>Alt</keycap><keycap>Down</keycap></keycombo>
+ * (the Down key in the numeric keypad also works).
+ * </para>
+ * <variablelist role="params">
+ * <varlistentry>
+ * <term><parameter>chooser</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * the object which received the signal.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * <varlistentry>
+ * <term><parameter>user_data</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * user data set when the signal handler was connected.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * </variablelist>
+ * </refsect3>
+ * <refsect3 id="GtkFileChooserDefault-home-folder">
+ * <title>The "GtkFileChooserDefault::home-folder" signal</title>
+ * <programlisting>
+ * void user_function (GtkFileChooserDefault *chooser,
+ * <link linkend="gpointer">gpointer</link> user_data);
+ * </programlisting>
+ * <para>
+ * This is used to make the file chooser show the user's home
+ * folder in the file list. By default this is bound to
+ * <keycombo><keycap>Alt</keycap><keycap>Home</keycap></keycombo>
+ * (the Home key in the numeric keypad also works).
+ * </para>
+ * <variablelist role="params">
+ * <varlistentry>
+ * <term><parameter>chooser</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * the object which received the signal.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * <varlistentry>
+ * <term><parameter>user_data</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * user data set when the signal handler was connected.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * </variablelist>
+ * </refsect3>
+ * <refsect3 id="GtkFileChooserDefault-desktop-folder">
+ * <title>The "GtkFileChooserDefault::desktop-folder" signal</title>
+ * <programlisting>
+ * void user_function (GtkFileChooserDefault *chooser,
+ * <link linkend="gpointer">gpointer</link> user_data);
+ * </programlisting>
+ * <para>
+ * This is used to make the file chooser show the user's Desktop
+ * folder in the file list. By default this is bound to
+ * <keycombo><keycap>Alt</keycap><keycap>D</keycap></keycombo>.
+ * </para>
+ * <variablelist role="params">
+ * <varlistentry>
+ * <term><parameter>chooser</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * the object which received the signal.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * <varlistentry>
+ * <term><parameter>user_data</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * user data set when the signal handler was connected.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * </variablelist>
+ * </refsect3>
+ * <refsect3 id="GtkFileChooserDefault-quick-bookmark">
+ * <title>The "GtkFileChooserDefault::quick-bookmark" signal</title>
+ * <programlisting>
+ * void user_function (GtkFileChooserDefault *chooser,
+ * gint bookmark_index,
+ * <link linkend="gpointer">gpointer</link> user_data);
+ * </programlisting>
+ * <para>
+ * This is used to make the file chooser switch to the bookmark
+ * specified in the <parameter>bookmark_index</parameter> parameter.
+ * For example, if you have three bookmarks, you can pass 0, 1, 2 to
+ * this signal to switch to each of them, respectively. By default this is bound to
+ * <keycombo><keycap>Alt</keycap><keycap>1</keycap></keycombo>,
+ * <keycombo><keycap>Alt</keycap><keycap>2</keycap></keycombo>,
+ * etc. until
+ * <keycombo><keycap>Alt</keycap><keycap>0</keycap></keycombo>. Note
+ * that in the default binding,
+ * that <keycombo><keycap>Alt</keycap><keycap>1</keycap></keycombo> is
+ * actually defined to switch to the bookmark at index 0, and so on
+ * successively;
+ * <keycombo><keycap>Alt</keycap><keycap>0</keycap></keycombo> is
+ * defined to switch to the bookmark at index 10.
+ * </para>
+ * <variablelist role="params">
+ * <varlistentry>
+ * <term><parameter>chooser</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * the object which received the signal.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * <varlistentry>
+ * <term><parameter>bookmark_indes</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * index of the bookmark to switch to; the indices start at 0.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * <varlistentry>
+ * <term><parameter>user_data</parameter> :</term>
+ * <listitem>
+ * <simpara>
+ * user data set when the signal handler was connected.
+ * </simpara>
+ * </listitem>
+ * </varlistentry>
+ * </variablelist>
+ * </refsect3>
+ * </refsect2>
+ */