Add subclass implementation for MenuButton

This way it will be possible to subclass a MenuButton

Author: nacho

gtk/src/subclass/menu_button.rs

@@ -0,0 +1,18 @@
+// Take a look at the license at the top of the repository in the LICENSE file.
+
+use glib::subclass::prelude::*;
+
+use super::toggle_button::ToggleButtonImpl;
+use crate::MenuButton;
+
+pub trait MenuButtonImpl: MenuButtonImplExt + ToggleButtonImpl {}
+
+pub trait MenuButtonImplExt: ObjectSubclass {}
+
+impl<T: MenuButtonImpl> MenuButtonImplExt for T {}
+
+unsafe impl<T: MenuButtonImpl> IsSubclassable<T> for MenuButton {
+    fn class_init(class: &mut glib::Class<Self>) {
+        Self::parent_class_init::<T>(class);
+    }
+}

gtk/src/subclass/mod.rs

@@ -24,6 +24,7 @@ pub mod header_bar;
 pub mod icon_view;
 pub mod list_box;
 pub mod list_box_row;
+pub mod menu_button;
 #[cfg(any(gdk_backend = "x11", feature = "dox"))]
 pub mod plug;
 pub mod scrolled_window;
@@ -65,6 +66,7 @@ pub mod prelude {
     pub use super::icon_view::{IconViewImpl, IconViewImplExt};
     pub use super::list_box::{ListBoxImpl, ListBoxImplExt};
     pub use super::list_box_row::{ListBoxRowImpl, ListBoxRowImplExt};
+    pub use super::menu_button::MenuButtonImpl;
     #[cfg(any(gdk_backend = "x11", feature = "dox"))]
     pub use super::plug::{PlugImpl, PlugImplExt};
     pub use super::scrolled_window::{ScrolledWindowImpl, ScrolledWindowImplExt};