[glibmm/glibmm-2-62] Glib::Property_ReadOnly: get_proxy() can be const

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 2941109605f39d736e3b0e2abed679d184cf5099
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Mon Sep 16 13:57:39 2019 +0200

    Glib::Property_ReadOnly: get_proxy() can be const
    
    Compare commit bfe785f44dffd7fcd4457f96b7b927092d08ee55 by Daniel Boles.

 glib/glibmm/property.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)
---
diff --git a/glib/glibmm/property.h b/glib/glibmm/property.h
index baf09f84..a370d3c9 100644
--- a/glib/glibmm/property.h
+++ b/glib/glibmm/property.h
@@ -271,9 +271,14 @@ public:
    */
   inline operator PropertyType() const;
 
+  //TODO: Remove the non-const get_proxy() when we can break ABI.
   /** Returns a proxy object that can be used to read this property.
    */
   inline Glib::PropertyProxy_ReadOnly<T> get_proxy();
+
+  /** Returns a proxy object that can be used to read this property.
+   */
+  inline Glib::PropertyProxy_ReadOnly<T> get_proxy() const;
 };
 
 /** See Property.
@@ -467,6 +472,13 @@ Property_ReadOnly<T>::get_proxy()
   return Glib::PropertyProxy_ReadOnly<T>(object_, get_name_internal());
 }
 
+template <class T>
+inline Glib::PropertyProxy_ReadOnly<T>
+Property_ReadOnly<T>::get_proxy() const
+{
+  return Glib::PropertyProxy_ReadOnly<T>(object_, get_name_internal());
+}
+
 /**** Glib::Property_WriteOnly<T> ****************************************************/
 
 template <class T>