[glibmm] Gio::Action, ActionGroup: Fix critical messages from vfuncs

[Kjell Ahlstedt <kjellahl src gnome org>]

commit b28bc49e7af2b90d23bb4ea460ca15c8eaf0cc54
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Tue Mar 17 10:33:18 2015 +0100

    Gio::Action, ActionGroup: Fix critical messages from vfuncs
    
    * glib/glibmm/wrap.h: Add unwrap_copy(const T& obj).
    * gio/src/action.hg:
    * gio/src/actiongroup.hg: Make vfuncs that return a GVariant* use the
    new Glib::unwrap_copy() overload by adding the _WRAP_VFUNC parameter
    refreturn_ctype. It avoids a critical message if Glib::VariantBase::
    gobj() == 0, which is not an error in these functions. Bug #705124.

 gio/src/action.hg      |    6 ++----
 gio/src/actiongroup.hg |    5 ++---
 glib/glibmm/wrap.h     |   17 ++++++++++++++---
 3 files changed, 18 insertions(+), 10 deletions(-)
---
diff --git a/gio/src/action.hg b/gio/src/action.hg
index 207bb93..eca9812 100644
--- a/gio/src/action.hg
+++ b/gio/src/action.hg
@@ -222,13 +222,11 @@ public:
   _WRAP_VFUNC(Glib::VariantType get_parameter_type() const, "get_parameter_type", keep_return)
   _WRAP_VFUNC(Glib::VariantType get_state_type() const, "get_state_type", keep_return)
 
-#m4 _CONVERSION(`Glib::VariantBase',`GVariant*',`$3.gobj_copy()')
-
-  _WRAP_VFUNC(Glib::VariantBase get_state_hint() const, "get_state_hint")
+  _WRAP_VFUNC(Glib::VariantBase get_state_hint() const, "get_state_hint", refreturn_ctype)
 
   _WRAP_VFUNC(bool get_enabled() const, "get_enabled")
 
-  _WRAP_VFUNC(Glib::VariantBase get_state() const, "get_state")
+  _WRAP_VFUNC(Glib::VariantBase get_state() const, "get_state", refreturn_ctype)
 
 #m4 _CONVERSION(`GVariant*',`const Glib::VariantBase&',`Glib::wrap($3, true)')
   _WRAP_VFUNC(void change_state(const Glib::VariantBase& value), "change_state")
diff --git a/gio/src/actiongroup.hg b/gio/src/actiongroup.hg
index a7483ba..71385be 100644
--- a/gio/src/actiongroup.hg
+++ b/gio/src/actiongroup.hg
@@ -152,9 +152,8 @@ public:
   _WRAP_VFUNC(Glib::VariantType get_action_parameter_type(const Glib::ustring& name) const, 
"get_action_parameter_type", keep_return)
   _WRAP_VFUNC(Glib::VariantType get_action_state_type(const Glib::ustring& name) const, 
"get_action_state_type", keep_return)
 
-#m4 _CONVERSION(`Glib::VariantBase',`GVariant*',`$3.gobj_copy()')
-  _WRAP_VFUNC(Glib::VariantBase get_action_state_hint(const Glib::ustring& name) const, 
"get_action_state_hint")
-  _WRAP_VFUNC(Glib::VariantBase get_action_state(const Glib::ustring& name) const, "get_action_state")
+  _WRAP_VFUNC(Glib::VariantBase get_action_state_hint(const Glib::ustring& name) const, 
"get_action_state_hint", refreturn_ctype)
+  _WRAP_VFUNC(Glib::VariantBase get_action_state(const Glib::ustring& name) const, "get_action_state", 
refreturn_ctype)
 
   _WRAP_VFUNC(void change_action_state(const Glib::ustring& name, const Glib::VariantBase& value), 
"change_action_state")
   _WRAP_VFUNC(void activate_action(const Glib::ustring& name, const Glib::VariantBase& parameter), 
"activate_action")
diff --git a/glib/glibmm/wrap.h b/glib/glibmm/wrap.h
index 5b07395..c4ca34e 100644
--- a/glib/glibmm/wrap.h
+++ b/glib/glibmm/wrap.h
@@ -1,9 +1,6 @@
-// -*- c++ -*-
 #ifndef _GLIBMM_WRAP_H
 #define _GLIBMM_WRAP_H
 
-/* $Id$ */
-
 /* Copyright (C) 1998-2002 The gtkmm Development Team
  *
  * This library is free software; you can redistribute it and/or
@@ -143,6 +140,20 @@ const typename T::BaseObjectType* unwrap(const Glib::RefPtr<const T>& ptr)
   return (ptr) ? ptr->gobj() : 0;
 }
 
+// This unwrap_copy() overload is intended primarily for classes wrapped as
+// _CLASS_BOXEDTYPE, _CLASS_OPAQUE_COPYABLE or _CLASS_OPAQUE_REFCOUNTED,
+// where the C++ objects are not stored in Glib::RefPtr<>s. They have a const
+// gobj_copy() member that returns a non-const pointer to the underlying C instance.
+/** Get the underlying C instance from the C++ instance and acquire a
+ * reference or copy. This is just like calling gobj_copy(), but it does its own
+ * check for a NULL pointer to the underlying C instance.
+ */
+template <class T> inline
+typename T::BaseObjectType* unwrap_copy(const T& obj)
+{
+  return obj.gobj() ? obj.gobj_copy() : 0;
+}
+
 /** Get the underlying C instance from the C++ instance and acquire a
  * reference.  This is just like calling gobj_copy(), but it does its own
  * check for a NULL pointer.