### Class

# Gtk Expander

#### Description [src]

    final class Gtk.Expander : Gtk.Widget
      implements Gtk.Accessible, Gtk.Buildable, Gtk.ConstraintTarget {
      /* No available fields */
    }

Allows the user to reveal or conceal a child widget.

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 `gtk_expander_set_child()` 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 `GtkExpander: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-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_ACCESSIBLE_ROLE_BUTTON` role.

#### Ancestors

- GtkWidget
- GInitiallyUnowned
- GObject

#### Implements

- GtkAccessible
- GtkBuildable
- GtkConstraintTarget

#### Constructors

###### gtk_expander_new

Creates a new expander using `label` as the text of the label.

###### gtk_expander_new_with_mnemonic

Creates a new expander using `label` as the text of the label.

#### Instance methods

###### gtk_expander_get_child

Gets the child widget of `expander`.

###### gtk_expander_get_expanded

Queries a `GtkExpander` and returns its current state.

###### gtk_expander_get_label

Fetches the text from a label widget.

###### gtk_expander_get_label_widget

Retrieves the label widget for the frame.

###### gtk_expander_get_resize_toplevel

Returns whether the expander will resize the toplevel widget containing the expander upon resizing and collapsing.

###### gtk_expander_get_use_markup

Returns whether the label’s text is interpreted as Pango markup.

###### gtk_expander_get_use_underline

Returns whether an underline in the text indicates a mnemonic.

###### gtk_expander_set_child

Sets the child widget of `expander`.

###### gtk_expander_set_expanded

Sets the state of the expander.

###### gtk_expander_set_label

Sets the text of the label of the expander to `label`.

###### gtk_expander_set_label_widget

Set the label widget for the expander.

###### gtk_expander_set_resize_toplevel

Sets whether the expander will resize the toplevel widget containing the expander upon resizing and collapsing.

###### gtk_expander_set_use_markup

Sets whether the text of the label contains Pango markup.

###### gtk_expander_set_use_underline

If true, an underline in the text indicates a mnemonic.

##### Methods inherited from GtkWidget (164)

Please see GtkWidget for a full list of methods.

##### Methods inherited from GObject (43)

Please see GObject for a full list of methods.

##### Methods inherited from GtkAccessible (20)

###### gtk_accessible_announce

Requests the user’s screen reader to announce the given message.

since: 4.14

###### gtk_accessible_get_accessible_parent

Retrieves the accessible parent for an accessible object.

since: 4.10

###### gtk_accessible_get_accessible_role

Retrieves the accessible role of an accessible object.

###### gtk_accessible_get_at_context

Retrieves the implementation for the given accessible object.

since: 4.10

###### gtk_accessible_get_bounds

Queries the coordinates and dimensions of this accessible.

since: 4.10

###### gtk_accessible_get_first_accessible_child

Retrieves the first accessible child of an accessible object.

since: 4.10

###### gtk_accessible_get_next_accessible_sibling

Retrieves the next accessible sibling of an accessible object.

since: 4.10

###### gtk_accessible_get_platform_state

Queries a platform state, such as focus.

since: 4.10

###### gtk_accessible_reset_property

Resets the accessible property to its default value.

###### gtk_accessible_reset_relation

Resets the accessible relation to its default value.

###### gtk_accessible_reset_state

Resets the accessible state to its default value.

###### gtk_accessible_set_accessible_parent

Sets the parent and sibling of an accessible object.

since: 4.10

###### gtk_accessible_update_next_accessible_sibling

Updates the next accessible sibling.

since: 4.10

###### gtk_accessible_update_platform_state

Informs ATs that the platform state has changed.

since: 4.18

###### gtk_accessible_update_property

Updates a list of accessible properties.

###### gtk_accessible_update_property_value

Updates an array of accessible properties.

###### gtk_accessible_update_relation

Updates a list of accessible relations.

###### gtk_accessible_update_relation_value

Updates an array of accessible relations.

###### gtk_accessible_update_state

Updates a list of accessible states.

###### gtk_accessible_update_state_value

Updates an array of accessible states.

##### Methods inherited from GtkBuildable (1)

###### gtk_buildable_get_buildable_id

Gets the ID of the `buildable` object.

#### Properties

###### Gtk.Expander:child

The child widget.

###### Gtk.Expander:expanded

Whether the expander has been opened to reveal the child.

###### Gtk.Expander:label

The text of the expanders label.

###### Gtk.Expander:label-widget

A widget to display instead of the usual expander label.

###### Gtk.Expander:resize-toplevel

When this property is `TRUE`, the expander will resize the toplevel widget containing the expander upon expanding and collapsing.

###### Gtk.Expander:use-markup

Whether the text in the label is Pango markup.

###### Gtk.Expander:use-underline

Whether an underline in the text indicates a mnemonic.

##### Properties inherited from GtkWidget (35)

###### Gtk.Widget:can-focus

Whether the widget or any of its descendents can accept the input focus.

###### Gtk.Widget:can-target

Whether the widget can receive pointer events.

###### Gtk.Widget:css-classes

A list of css classes applied to this widget.

###### Gtk.Widget:css-name

The name of this widget in the CSS tree.

###### Gtk.Widget:cursor

The cursor used by `widget`.

###### Gtk.Widget:focus-on-click

Whether the widget should grab focus when it is clicked with the mouse.

###### Gtk.Widget:focusable

Whether this widget itself will accept the input focus.

###### Gtk.Widget:halign

How to distribute horizontal space if widget gets extra space.

###### Gtk.Widget:has-default

Whether the widget is the default widget.

###### Gtk.Widget:has-focus

Whether the widget has the input focus.

###### Gtk.Widget:has-tooltip

Enables or disables the emission of the `GtkWidget::query-tooltip` signal on `widget`.

###### Gtk.Widget:height-request

Overrides for height request of the widget.

###### Gtk.Widget:hexpand

Whether to expand horizontally.

###### Gtk.Widget:hexpand-set

Whether to use the `hexpand` property.

###### Gtk.Widget:layout-manager

The `GtkLayoutManager` instance to use to compute the preferred size of the widget, and allocate its children.

###### Gtk.Widget:limit-events

Makes this widget act like a modal dialog, with respect to event delivery.

since: 4.18

###### Gtk.Widget:margin-bottom

Margin on bottom side of widget.

###### Gtk.Widget:margin-end

Margin on end of widget, horizontally.

###### Gtk.Widget:margin-start

Margin on start of widget, horizontally.

###### Gtk.Widget:margin-top

Margin on top side of widget.

###### Gtk.Widget:name

The name of the widget.

###### Gtk.Widget:opacity

The requested opacity of the widget.

###### Gtk.Widget:overflow

How content outside the widget’s content area is treated.

###### Gtk.Widget:parent

The parent widget of this widget.

###### Gtk.Widget:receives-default

Whether the widget will receive the default action when it is focused.

###### Gtk.Widget:root

The `GtkRoot` widget of the widget tree containing this widget.

###### Gtk.Widget:scale-factor

The scale factor of the widget.

###### Gtk.Widget:sensitive

Whether the widget responds to input.

###### Gtk.Widget:tooltip-markup

Sets the text of tooltip to be the given string, which is marked up with Pango markup.

###### Gtk.Widget:tooltip-text

Sets the text of tooltip to be the given string.

###### Gtk.Widget:valign

How to distribute vertical space if widget gets extra space.

###### Gtk.Widget:vexpand

Whether to expand vertically.

###### Gtk.Widget:vexpand-set

Whether to use the `vexpand` property.

###### Gtk.Widget:visible

Whether the widget is visible.

###### Gtk.Widget:width-request

Overrides for width request of the widget.

##### Properties inherited from GtkAccessible (1)

###### GtkAccessible:accessible-role

The accessible role of the given `GtkAccessible` implementation.

#### Signals

###### Gtk.Expander::activate

Activates the `GtkExpander`.

##### Signals inherited from GtkWidget (13)

###### GtkWidget::destroy

Signals that all holders of a reference to the widget should release the reference that they hold.

###### GtkWidget::direction-changed

Emitted when the text direction of a widget changes.

###### GtkWidget::hide

Emitted when `widget` is hidden.

###### GtkWidget::keynav-failed

Emitted if keyboard navigation fails.

###### GtkWidget::map

Emitted when `widget` is going to be mapped.

###### GtkWidget::mnemonic-activate

Emitted when a widget is activated via a mnemonic.

###### GtkWidget::move-focus

Emitted when the focus is moved.

###### GtkWidget::query-tooltip

Emitted when the widget’s tooltip is about to be shown.

###### GtkWidget::realize

Emitted when `widget` is associated with a `GdkSurface`.

###### GtkWidget::show

Emitted when `widget` is shown.

###### GtkWidget::state-flags-changed

Emitted when the widget state changes.

###### GtkWidget::unmap

Emitted when `widget` is going to be unmapped.

###### GtkWidget::unrealize

Emitted when the `GdkSurface` associated with `widget` is destroyed.

##### Signals inherited from GObject (1)

###### GObject::notify

The notify signal is emitted on an object when one of its properties has its value set through g_object_set_property(), g_object_set(), et al.