main.vala

public void main () {
    Gtk.init ();

    var button = workbench.builder.get_object ("button") as Gtk.Button;
    button.clicked.connect (on_button_clicked);
}

public void on_button_clicked () {
    var dialog = new Adw.AboutDialog () {
        application_icon = "application-x-executable",
        application_name = "Typeset",
        developer_name = "Angela Avery",
        version = "1.2.3",
        comments = "Typeset is an app that doesn’t exist and is used as an example content for About Dialog.",
        website = "https://example.org",
        issue_url = "https://example.org",
        support_url = "https://example.org",
        copyright = "© 2023 Angela Avery",
        license_type = Gtk.License.GPL_3_0_ONLY,
        developers = { "Angela Avery <angela@example.org>" },
        artists = { "GNOME Design Team" },
        translator_credits = "translator-credits",
    };
    dialog.add_link (
                     "Documentation",
                     "https://gnome.pages.gitlab.gnome.org/libadwaita/doc/1.6/class.AboutDialog.html"
    );
    dialog.add_legal_section (
                              "Fonts",
                              null,
                              Gtk.License.CUSTOM,
                              "This application uses font data from <a href='https://example.org'>somewhere</a>."
    );

    dialog.add_acknowledgement_section ("Special thanks to", { "My cat" });

    dialog.present (workbench.window);
}