Expander

Object Hierarchy:

Description:

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

`GtkExpander` allows the user to reveal its child by clicking on an expander triangle.

![An example GtkExpander](expander.png)

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 [method@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 [ property@Gtk.Expander:expanded] property which can be used to monitor its expansion state. You should watch this property with a signal connection as follows:

```c 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:

```xml <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 `GtkExpander:checked` pseudoclass set on it.

Accessibility

`GtkExpander` uses the gtk_accessible_role_button role.

Namespace: Gtk

Package: gtk4

Content:

Properties:

public Widget child { get; set; }
The child widget.
public bool expanded { get; set construct; }
Whether the expander has been opened to reveal the child.
public string label { get; set construct; }
The text of the expanders label.
public Widget label_widget { get; set; }
A widget to display instead of the usual expander label.
public bool resize_toplevel { get; set; }
When this property is true, the expander will resize the toplevel widget containing the expander upon expanding and collapsing.
public bool use_markup { get; set construct; }
Whether the text in the label is Pango markup.
public bool use_underline { get; set construct; }
Whether an underline in the text indicates a mnemonic.

Creation methods:

public Expander (string? label)
Creates a new expander using label as the text of the label.
public Expander.with_mnemonic (string? label)
Creates a new expander using label as the text of the label.

Methods:

public unowned Widget? get_child ()
Gets the child widget of this.
public bool get_expanded ()
Queries a `GtkExpander` and returns its current state.
public unowned string? get_label ()
Fetches the text from a label widget.
public unowned Widget? get_label_widget ()
Retrieves the label widget for the frame.
public bool get_resize_toplevel ()
Returns whether the expander will resize the toplevel widget containing the expander upon resizing and collapsing.
public bool get_use_markup ()
Returns whether the label’s text is interpreted as Pango markup.
public bool get_use_underline ()
Returns whether an underline in the text indicates a mnemonic.
public void set_child (Widget? child)
Sets the child widget of this.
public void set_expanded (bool expanded)
Sets the state of the expander.
public void set_label (string? label)
Sets the text of the label of the expander to label.
public void set_label_widget (Widget? label_widget)
Set the label widget for the expander.
public void set_resize_toplevel (bool resize_toplevel)
Sets whether the expander will resize the toplevel widget containing the expander upon resizing and collapsing.
public void set_use_markup (bool use_markup)
Sets whether the text of the label contains Pango markup.
public void set_use_underline (bool use_underline)
If true, an underline in the text indicates a mnemonic.

Signals:

public signal void activate ()
Activates the `GtkExpander`.

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