Glib: Add some Glib::Value<> specializations

* glib/glibmm/error.[cc|h]: Add operator bool(). Add Glib::Value<Glib::Error>
which is needed in _WRAP_PROPERTY() in Gtk::MediaStream.
* glib/glibmm/objectbase.[cc|h]: Add get_base_type(), which is necessary for
one of the existing Value<> specializations to apply. ObjectBase is used
in _WRAP_PROPERTY() in Glib::Binding.
* glib/src/variant.[ccg|hg]: Add Glib::Value<VariantBase> which is
needed in _WRAP_PROPERTY() in Gio:Action.
* glib/src/varianttype.[ccg|hg]: Add Glib::Value<VariantType> which is
needed in _WRAP_PROPERTY() in Gio:Action.

All data types that occur in _WRAP_PROPERTY() must have correct Glib::Value<>
specializations. In most cases missing Value<> specializations are noticed
only during execution of code that calls an affected property_*() method.

1 files changed, 18 insertions, 0 deletions

diff --git a/glib/src/varianttype.ccg b/glib/src/varianttype.ccg
index ff1784fa..cd45bd5f 100644
--- a/glib/src/varianttype.ccg
+++ b/glib/src/varianttype.ccg
@@ -136,4 +136,22 @@ std::vector<VariantType> VariantType::get_item_types() const
   return result;
 }
 
+// Glib::Value<Glib::VariantType>
+GType Value<VariantType>::value_type()
+{
+  // The type function is *not* called g_variant_type_get_type().
+  // Use the macro in order to avoid using the non-standard function name here.
+  return G_TYPE_VARIANT_TYPE;
+}
+
+void Value<VariantType>::set(const CppType& data)
+{
+  set_boxed(data.gobj());
+}
+
+Value<VariantType>::CppType Value<VariantType>::get() const
+{
+  return Glib::wrap(static_cast<CType>(get_boxed()), true);
+}
+
 } // namespace GLib