[glibmm] Glib::Value: Add ValueBase_Variant

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 9d894e30007c54622c73ed7619c3d868e3351b35
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Sun Jan 20 16:29:30 2019 +0100

    Glib::Value: Add ValueBase_Variant
    
    Nice to have as a base class for Value<VariantBase> and possibly for future
    Glib::Value specializations.

 glib/glibmm/value.cc | 29 +++++++++++++++++++++++++++++
 glib/glibmm/value.h  | 21 ++++++++++++++++++++-
 glib/src/variant.ccg | 21 ++-------------------
 glib/src/variant.hg  | 14 +++-----------
 4 files changed, 54 insertions(+), 31 deletions(-)
---
diff --git a/glib/glibmm/value.cc b/glib/glibmm/value.cc
index 75685fda..d111b184 100644
--- a/glib/glibmm/value.cc
+++ b/glib/glibmm/value.cc
@@ -244,6 +244,35 @@ ValueBase_String::create_param_spec(const Glib::ustring& name,
       get_cstring(), static_cast<GParamFlags>(flags));
 }
 
+/**** Glib::ValueBase_Variant ************************************************/
+
+// static
+GType ValueBase_Variant::value_type()
+{
+  return G_TYPE_VARIANT;
+}
+
+void ValueBase_Variant::set_variant(GVariant* data)
+{
+  g_value_set_variant(&gobject_, data);
+}
+
+GVariant* ValueBase_Variant::get_variant() const
+{
+  return g_value_get_variant(&gobject_);
+}
+
+GParamSpec* ValueBase_Variant::create_param_spec(const Glib::ustring& name,
+  const Glib::ustring& nick, const Glib::ustring& blurb, Glib::ParamFlags flags) const
+{
+  GVariant* gvariant = g_value_get_variant(&gobject_);
+  const GVariantType* gvariant_type = gvariant ? g_variant_get_type(gvariant) : G_VARIANT_TYPE_ANY;
+
+  return g_param_spec_variant(
+    name.c_str(), c_str_or_nullptr(nick), c_str_or_nullptr(blurb),
+    gvariant_type, gvariant, static_cast<GParamFlags>(flags));
+}
+
 /**** Glib::Value<std::string> *********************************************/
 
 void
diff --git a/glib/glibmm/value.h b/glib/glibmm/value.h
index 6882db4c..fb504342 100644
--- a/glib/glibmm/value.h
+++ b/glib/glibmm/value.h
@@ -184,9 +184,28 @@ protected:
   const char* get_cstring() const; // never returns nullptr
 };
 
+/**
+ * @ingroup glibmmValue
+ */
+class ValueBase_Variant : public ValueBase
+{
+public:
+  static GType value_type() G_GNUC_CONST;
+
+#ifndef DOXYGEN_SHOULD_SKIP_THIS
+  GParamSpec* create_param_spec(const Glib::ustring& name, const Glib::ustring& nick,
+                                const Glib::ustring& blurb, Glib::ParamFlags flags) const;
+#endif
+
+protected:
+  void set_variant(GVariant* data);
+  GVariant* get_variant() const; // doesn't copy, may return nullptr
+};
+
+
 } // namespace Glib
 
-/* Include generic Glib::Value<> template, before any specializations:
+/* Include primary Glib::Value<> template, before any specializations:
  */
 #define _GLIBMM_VALUE_H_INCLUDE_VALUE_CUSTOM_H
 #include <glibmm/value_custom.h>
diff --git a/glib/src/variant.ccg b/glib/src/variant.ccg
index ec3fc94a..299a9393 100644
--- a/glib/src/variant.ccg
+++ b/glib/src/variant.ccg
@@ -694,31 +694,14 @@ Variant<type_vec_string>::get_iter() const
 
 /*---------------------Value<Glib::VariantBase>---------------------*/
 
-// static
-GType Value<VariantBase>::value_type()
-{
-  return G_TYPE_VARIANT;
-}
-
 void Value<VariantBase>::set(CppType data)
 {
-  g_value_set_variant(&gobject_, data.gobj());
+  set_variant(data.gobj());
 }
 
 Value<VariantBase>::CppType Value<VariantBase>::get() const
 {
-  return CppType(g_value_get_variant(&gobject_), true);
-}
-
-GParamSpec* Value<VariantBase>::create_param_spec(const Glib::ustring& name,
-  const Glib::ustring& nick, const Glib::ustring& blurb, Glib::ParamFlags flags) const
-{
-  GVariant* gvariant = g_value_get_variant(&gobject_);
-  const GVariantType* gvariant_type = gvariant ? g_variant_get_type(gvariant) : G_VARIANT_TYPE_ANY;
-
-  return g_param_spec_variant(
-    name.c_str(), c_str_or_nullptr(nick), c_str_or_nullptr(blurb),
-    gvariant_type, gvariant, static_cast<GParamFlags>(flags));
+  return CppType(get_variant(), true);
 }
 
 } // namespace Glib
diff --git a/glib/src/variant.hg b/glib/src/variant.hg
index be42eb83..d570dcb8 100644
--- a/glib/src/variant.hg
+++ b/glib/src/variant.hg
@@ -1588,26 +1588,18 @@ VariantIter Variant<std::tuple<Types...>>::get_iter() const
   return VariantContainerBase::get_iter(type);
 }
 
-/*---------------------Value<Glib::VariantBase>---------------------*/
-
+#ifndef DOXYGEN_SHOULD_SKIP_THIS
 // This is needed so Glib::VariantBase can be used with
 // Glib::Value and _WRAP_PROPERTY in Gio::Action and elsewhere.
 template <>
-class Value<Glib::VariantBase> : public ValueBase
+class Value<Glib::VariantBase> : public ValueBase_Variant
 {
 public:
   using CppType = Glib::VariantBase;
-  using CType = GVariant*;
-
-  static GType value_type() G_GNUC_CONST;
 
   void set(CppType data);
   CppType get() const;
-
-#ifndef DOXYGEN_SHOULD_SKIP_THIS
-  GParamSpec* create_param_spec(const Glib::ustring& name, const Glib::ustring& nick,
-                                const Glib::ustring& blurb, Glib::ParamFlags flags) const;
-#endif
 };
+#endif /* DOXYGEN_SHOULD_SKIP_THIS */
 
 } // namespace Glib