TreeExpander

Object Hierarchy:

Description:

[ CCode ( type_id = "gtk_tree_expander_get_type ()" ) ]
public sealed class TreeExpander : Widget, Accessible, Buildable, ConstraintTarget

Provides an expander for a tree-like 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 [ class@Gtk.TreeListModel]. `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 [property@Gtk.ListItem: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 [class@Gtk.TreeListRow] items which can be set via [ method@Gtk.TreeExpander.set_list_row] on the expander. The expander will then watch that row item automatically. [ method@Gtk.TreeExpander.set_child] sets the widget that displays the actual row contents.

`GtkTreeExpander` can be modified with properties such as [property@Gtk.TreeExpander:indent-for-icon], [ property@Gtk.TreeExpander:indent-for-depth], and [property@Gtk.TreeExpander:hide-expander] to achieve a different appearance. This can even be done to influence individual rows, for example by binding the [property@Gtk.TreeExpander: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.

Shortcuts and Gestures

`GtkTreeExpander` supports the following keyboard shortcuts:

<kbd>+</kbd> or <kbd>*</kbd> expands the expander.
<kbd>-</kbd> or <kbd>/</kbd> collapses the expander.
Left and right arrow keys, when combined with <kbd>Shift</kbd> or <kbd>Ctrl</kbd>+<kbd>Shift</kbd>, will expand or collapse, depending on the locale's text direction.
<kbd>Ctrl</kbd>+<kbd>␣</kbd> toggles the expander state.

The row can also expand on drag gestures.

Actions

`GtkTreeExpander` defines a set of built-in actions:

`listitem.expand` expands the expander if it can be expanded.
`listitem.collapse` collapses the expander.
`listitem.toggle-expand` tries to expand the expander if it was collapsed or collapses it if it was expanded.

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 `GtkTreeExpander: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 [enum@Gtk.AccessibleRole.group] role.

Since GTK 4.12, `GtkTreeExpander` uses the [enum@Gtk.AccessibleRole.button] role. Toggling it will change the `GTK_ACCESSIBLE_STATE_EXPANDED` state.

Namespace: Gtk

Package: gtk4

Content:

Properties:

public Widget child { get; set; }
The child widget with the actual contents.
public bool hide_expander { get; set; }
Whether the expander icon should be hidden in a GtkTreeListRow.
public bool indent_for_depth { get; set; }
TreeExpander indents the child according to its depth.
public bool indent_for_icon { get; set; }
TreeExpander indents the child by the width of an expander-icon if it is not expandable.
public Object item { owned get; }
The item held by this expander's row.
public TreeListRow list_row { get; set; }
The list row to track for expander state.

Creation methods:

public TreeExpander ()
Creates a new `GtkTreeExpander`

Methods:

public unowned Widget? get_child ()
Gets the child widget displayed by this.
public bool get_hide_expander ()
Gets whether the TreeExpander should be hidden in a GtkTreeListRow.
public bool get_indent_for_depth ()
TreeExpander indents each level of depth with an additional indent.
public bool get_indent_for_icon ()
TreeExpander indents the child by the width of an expander-icon if it is not expandable.
public Object? get_item ()
Forwards the item set on the `GtkTreeListRow` that this is managing.
public unowned TreeListRow? get_list_row ()
Gets the list row managed by this.
public void set_child (Widget? child)
Sets the content widget to display.
public void set_hide_expander (bool hide_expander)
Sets whether the expander icon should be visible in a GtkTreeListRow.
public void set_indent_for_depth (bool indent_for_depth)
Sets if the TreeExpander should indent the child according to its depth.
public void set_indent_for_icon (bool indent_for_icon)
Sets if the TreeExpander should indent the child by the width of an expander-icon when it is not expandable.
public void set_list_row (TreeListRow? list_row)
Sets the tree list row that this expander should manage.

Inherited Members:

All known members inherited from class Gtk.Widget

All known members inherited from class GLib.Object

All known members inherited from interface Gtk.Accessible

All known members inherited from interface Gtk.Buildable