Expander


Object Hierarchy:

Object hierarchy for Expander

Description:

public class Expander : Bin, Implementor, Buildable

A Expander allows the user to hide or show its child by clicking on an expander triangle similar to the triangles used in a TreeView.

Normally you use an expander as you would use any other descendant of Bin; you create the child widget and use add to add it to the expander. When the expander is toggled, it will take care of showing and hiding the child automatically.

Special Usage

There are situations in which you may prefer to show and hide the expanded widget yourself, such as when you want to actually create the widget at expansion time. In this case, create a Expander but do not add a child to it. The expander widget has an expanded property which can be used to monitor its expansion state. You should watch this property with a signal connection as follows:

static void
expander_callback (GObject *object,
GParamSpec *param_spec,
gpointer user_data)
{
GtkExpander *expander;

expander = GTK_EXPANDER (object);

if (gtk_expander_get_expanded (expander))
{
// Show or create widgets
}
else
{
// Hide or destroy widgets
}
}

static void
create_expander (void)
{
GtkWidget *expander = gtk_expander_new_with_mnemonic ("_More Options");
g_signal_connect (expander, "notify::expanded",
G_CALLBACK (expander_callback), NULL);

// ...
}

GtkExpander as GtkBuildable

The GtkExpander implementation of the GtkBuildable interface supports placing a child in the label position by specifying “label” as the “type” attribute of a <child> element. A normal content child can be specified without specifying a <child> type attribute.

An example of a UI definition fragment with GtkExpander:

<object class="GtkExpander">
<child type="label">
<object class="GtkLabel" id="expander-label"/>
</child>
<child>
<object class="GtkEntry" id="expander-content"/>
</child>
</object>

CSS nodes

expander
├── title
│ ├── arrow
│ ╰── <label widget>
╰── <child>
nodes, the main node with the name expander, a subnode with name title and node below it with name arrow. The arrow of an expander that is showing its child gets the GtkExpander:checked pseudoclass added to it.

Example: Expander:

public class Application : Gtk.Window {
public Application () {
// Prepare Gtk.Window:
this.title = "My Gtk.Expander";
this.window_position = Gtk.WindowPosition.CENTER;
this.destroy.connect (Gtk.main_quit);
this.set_default_size (350, 70);

// The Expander:
Gtk.Expander expander = new Gtk.Expander ("<b>My secret area</b>");
expander.use_markup = true;
this.add (expander);

// Expander content:
Gtk.Label label = new Gtk.Label ("You found me!");
expander.add (label);
}

public static int main (string[] args) {
Gtk.init (ref args);

Application app = new Application ();
app.show_all ();
Gtk.main ();
return 0;
}
}

valac --pkg gtk+-3.0 Gtk.Expander.vala


Namespace: Gtk
Package: gtk+-3.0

Content:

Properties:

Creation methods:

Methods:

Signals:

Inherited Members:

All known members inherited from class Gtk.Bin
All known members inherited from class Gtk.Widget
All known members inherited from interface Atk.Implementor