### Class

# Gtk TreeExpander

#### Description [src]

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

`GtkTreeExpander` is a widget that provides an expander for a list.

It is typically placed as a bottommost child into a `GtkListView` to allow users to expand and collapse children in a list with a `GtkTreeListModel`. `GtkTreeExpander` provides the common UI elements, gestures and keybindings for this purpose.

On top of this, the “listitem.expand”, “listitem.collapse” and “listitem.toggle-expand” actions are provided to allow adding custom UI for managing expanded state.

It is important to mention that you want to set the `GtkListItem:focusable` property to FALSE when using this widget, as you want the keyboard focus to be in the treexpander, and not inside the list to make use of the keybindings.

The `GtkTreeListModel` must be set to not be passthrough. Then it will provide `GtkTreeListRow` items which can be set via `gtk_tree_expander_set_list_row()` on the expander. The expander will then watch that row item automatically. `gtk_tree_expander_set_child()` sets the widget that displays the actual row contents.

`GtkTreeExpander` can be modified with properties such as `GtkTreeExpander:indent-for-icon`, `GtkTreeExpander:indent-for-depth`, and `GtkTreeExpander:hide-expander` to achieve a different appearance. This can even be done to influence individual rows, for example by binding the `GtkTreeExpander:hide-expander` property to the item count of the model of the treelistrow, to hide the expander for rows without children, even if the row is expandable.

## CSS nodes

    treeexpander
    ├── [indent]*
    ├── [expander]
    ╰── <child>

`GtkTreeExpander` has zero or one CSS nodes with the name “expander” that should display the expander icon. The node will be `:checked` when it is expanded. If the node is not expandable, an “indent” node will be displayed instead.

For every level of depth, another “indent” node is prepended.

## Accessibility

Until GTK 4.10, `GtkTreeExpander` used the `GTK_ACCESSIBLE_ROLE_GROUP` role.

Since GTK 4.12, `GtkTreeExpander` uses the `GTK_ACCESSIBLE_ROLE_BUTTON` role. Toggling it will change the `GTK_ACCESSIBLE_STATE_EXPANDED` state.

#### Hierarchy

#### Ancestors

- GtkWidget
- GInitiallyUnowned
- GObject

#### Implements

- GtkAccessible
- GtkBuildable
- GtkConstraintTarget

#### Constructors

###### gtk_tree_expander_new

Creates a new `GtkTreeExpander`

#### Instance methods

###### gtk_tree_expander_get_child

Gets the child widget displayed by `self`.

###### gtk_tree_expander_get_hide_expander

Gets whether the TreeExpander should be hidden in a GtkTreeListRow.

since: 4.10

###### gtk_tree_expander_get_indent_for_depth

TreeExpander indents each level of depth with an additional indent.

since: 4.10

###### gtk_tree_expander_get_indent_for_icon

TreeExpander indents the child by the width of an expander-icon if it is not expandable.

since: 4.6

###### gtk_tree_expander_get_item

Forwards the item set on the `GtkTreeListRow` that `self` is managing.

###### gtk_tree_expander_get_list_row

Gets the list row managed by `self`.

###### gtk_tree_expander_set_child

Sets the content widget to display.

###### gtk_tree_expander_set_hide_expander

Sets whether the expander icon should be visible in a GtkTreeListRow.

since: 4.10

###### gtk_tree_expander_set_indent_for_depth

Sets if the TreeExpander should indent the child according to its depth.

since: 4.10

###### gtk_tree_expander_set_indent_for_icon

Sets if the TreeExpander should indent the child by the width of an expander-icon when it is not expandable.

since: 4.6

###### gtk_tree_expander_set_list_row

Sets the tree list row that this expander should manage.

##### Methods inherited from GtkWidget (162)

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 (19)

###### 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 accessible implementation for the given `GtkAccessible`.

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

Query 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 of `self`.

since: 4.10

###### 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. See the `GtkAccessibleState` documentation for the value types 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.TreeExpander:child

The child widget with the actual contents.

###### Gtk.TreeExpander:hide-expander

Whether the expander icon should be hidden in a GtkTreeListRow. Note that this property simply hides the icon. The actions and keybinding (i.e. collapse and expand) are not affected by this property.

since: 4.10

###### Gtk.TreeExpander:indent-for-depth

TreeExpander indents the child according to its depth.

since: 4.10

###### Gtk.TreeExpander:indent-for-icon

TreeExpander indents the child by the width of an expander-icon if it is not expandable.

since: 4.6

###### Gtk.TreeExpander:item

The item held by this expander’s row.

###### Gtk.TreeExpander:list-row

The list row to track for expander state.

##### Properties inherited from GtkWidget (34)

###### 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 ::query-tooltip signal on `widget`.

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

Override 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: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

Override for width request of the widget.

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

###### GtkAccessible:accessible-role

The accessible role of the given `GtkAccessible` implementation.

#### Signals

##### 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.

#### Class structure

    struct GtkTreeExpanderClass {
      GtkWidgetClass parent_class;

    }

No description available.

###### Class members

`parent_class: GtkWidgetClass`
  No description available.