[perl-Glib-Object-Introspection] Add Glib::Object::Introspection::GValueWrapper::get_value

[Torsten Schönfeld <tsch src gnome org>]

commit 8326a03eb50551b29de8657552ee6d133e799579
Author: Torsten Schönfeld <kaffeetisch gmx de>
Date:   Mon Oct 24 21:08:19 2016 +0200

    Add Glib::Object::Introspection::GValueWrapper::get_value
    
    To obtain the actual value of the wrapped GValue.  This is necessary
    when a functions expects an already set-up GValue and then modifies it
    to return a value.  Like Gtk3::Container::child_get_property.

 GObjectIntrospection.xs          |   10 ++++++++++
 lib/Glib/Object/Introspection.pm |   13 +++++++++++--
 t/values.t                       |   18 ++++++++++++++----
 3 files changed, 35 insertions(+), 6 deletions(-)
---
diff --git a/GObjectIntrospection.xs b/GObjectIntrospection.xs
index ef9b3e0..2361dc9 100644
--- a/GObjectIntrospection.xs
+++ b/GObjectIntrospection.xs
@@ -1039,6 +1039,16 @@ new (class, const gchar *type_package, SV *perl_value)
     OUTPUT:
        RETVAL
 
+SV *
+get_value (SV *sv)
+    PREINIT:
+       GValue *v;
+    CODE:
+       v = SvGValueWrapper (sv);
+       RETVAL = gperl_sv_from_value (v);
+    OUTPUT:
+       RETVAL
+
 void
 DESTROY (SV *sv)
     PREINIT:
diff --git a/lib/Glib/Object/Introspection.pm b/lib/Glib/Object/Introspection.pm
index 2347277..4b6e61b 100644
--- a/lib/Glib/Object/Introspection.pm
+++ b/lib/Glib/Object/Introspection.pm
@@ -673,12 +673,21 @@ wrapper for a function that expects a GValue, do this:
   ...
   my $type = ...; # somehow get the package name that
                   # corresponds to the correct GType
-  my $real_value =
+  my $wrapper =
     Glib::Object::Introspection::GValueWrapper->new ($type, $value);
   # now use Glib::Object::Introspection->invoke and
-  # substitute $real_value where you'd use $value
+  # substitute $wrapper where you'd use $value
   ...
 
+If you need to call a function that expects an already set-up GValue and
+modifies it, use C<get_value> on the wrapper afterwards to obtain the value.
+For example:
+
+  my $wrapper =
+    Glib::Object::Introspection::GValueWrapper->new ('Glib::Boolean', 0);
+  $box->child_get_property ($label, 'expand', $gvalue);
+  my $value = $gvalue->get_value
+
 =head2 Handling extendable enumerations
 
 If you need to handle extendable enumerations for which more than the
diff --git a/t/values.t b/t/values.t
index 36b813f..bb34369 100644
--- a/t/values.t
+++ b/t/values.t
@@ -5,10 +5,20 @@ BEGIN { require './t/inc/setup.pl' };
 use strict;
 use warnings;
 
-plan tests => 2;
+plan tests => 3;
 
-SKIP: {
-  skip 'SV → GValue not implemented', 1;
-  is (Regress::test_int_value_arg (23), 23);
+{
+  my $wrapper = Glib::Object::Introspection::GValueWrapper->new ('Glib::Int', 23);
+  is (Regress::test_int_value_arg ($wrapper), 23);
 }
+
 is (Regress::test_value_return (23), 23);
+
+SKIP: {
+  skip 'more GValue tests', 1
+    unless check_gi_version (1, 38, 0);
+
+  my $wrapper = Glib::Object::Introspection::GValueWrapper->new ('Glib::Int', 42);
+  GI::gvalue_in_with_modification ($wrapper);
+  is ($wrapper->get_value, 24);
+}