Package org.gnome.gtk

Class Expander

java.lang.Object
org.javagi.base.ProxyInstance
org.gnome.gobject.TypeInstance
org.gnome.gobject.GObject
org.gnome.gobject.InitiallyUnowned
org.gnome.gtk.Widget
org.gnome.gtk.Expander
All Implemented Interfaces:
Accessible, Buildable, ConstraintTarget, Proxy
@Generated("io.github.jwharm.JavaGI") public class Expander extends Widget implements Accessible, Buildable, ConstraintTarget
Allows the user to reveal or conceal a child widget.

An example GtkExpander

This is similar to the triangles used in a GtkTreeView.

Normally you use an expander as you would use a frame; you create the child widget and use setChild(org.gnome.gtk.Widget) 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 GtkExpander but do not add a child to it. The expander widget has an Gtk.Expander: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
An example of a UI definition fragment with GtkExpander: 

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

CSS nodes


 expander-widget
 ╰── box
     ├── title
     │   ├── expander
     │   ╰── <label widget>
     ╰── <child>

GtkExpander has a main node expander-widget, and subnode box containing the title and child widget. The box subnode title contains node expander, i.e. the expand/collapse arrow; then the label widget if any. The arrow of an expander that is showing its child gets the :checked pseudoclass set on it.

Accessibility
GtkExpander uses the Gtk.AccessibleRole.button role.