Issue #862 - gtk::Widget::size_allocate has an immutable allocation

Gir.toml

@@ -2331,6 +2331,11 @@ manual_traits = ["WidgetExtManual"]
     name = "get_style_context"
         [object.function.return]
         nullable = false
+    [[object.function]]
+    name = "size_allocate"
+        [[object.function.parameter]]
+        name = "allocation"
+        const = true
     [[object.signal]]
     name = "button-press-event"
     inhibit = true

src/auto/widget.rs

@@ -548,7 +548,7 @@ pub trait WidgetExt: 'static {
 
     fn show_now(&self);
 
-    fn size_allocate(&self, allocation: &mut Allocation);
+    fn size_allocate(&self, allocation: &Allocation);
 
     fn size_allocate_with_baseline(&self, allocation: &mut Allocation, baseline: i32);
 
@@ -2733,11 +2733,11 @@ impl<O: IsA<Widget>> WidgetExt for O {
         }
     }
 
-    fn size_allocate(&self, allocation: &mut Allocation) {
+    fn size_allocate(&self, allocation: &Allocation) {
         unsafe {
             gtk_sys::gtk_widget_size_allocate(
                 self.as_ref().to_glib_none().0,
-                allocation.to_glib_none_mut().0,
+                mut_override(allocation.to_glib_none().0),
             );
         }
     }