glib: Add connect_notify* methods to SignalGroup

Fixes #1021.

glib/src/gobject/signal_group.rs

@@ -42,6 +42,44 @@ impl SignalGroup {
         self.connect_closure(signal_name, after, RustClosure::new_local(callback));
     }
 
+    #[inline]
+    pub fn connect_notify<F>(&self, name: Option<&str>, callback: F)
+    where
+        F: Fn() + Send + Sync + 'static,
+    {
+        let signal_name = if let Some(name) = name {
+            format!("notify::{name}\0")
+        } else {
+            "notify\0".into()
+        };
+
+        let closure = crate::RustClosure::new(move |_| {
+            callback();
+            None
+        });
+
+        self.connect_closure(&signal_name, false, closure);
+    }
+
+    #[inline]
+    pub fn connect_notify_local<F>(&self, name: Option<&str>, callback: F)
+    where
+        F: Fn() + 'static,
+    {
+        let signal_name = if let Some(name) = name {
+            format!("notify::{name}\0")
+        } else {
+            "notify\0".into()
+        };
+
+        let closure = crate::RustClosure::new_local(move |_| {
+            callback();
+            None
+        });
+
+        self.connect_closure(&signal_name, false, closure);
+    }
+
     unsafe fn connect_bind_unsafe<F: Fn(&Self, &Object)>(&self, f: F) -> SignalHandlerId {
         unsafe extern "C" fn bind_trampoline<F: Fn(&SignalGroup, &Object)>(
             this: *mut crate::gobject_ffi::GSignalGroup,