Glib: value_custom: Use callback functions with C linkage

* glib/glibmm/value_custom.[cc|h]: Add custom_boxed_type_cpp_register().
* tests/glibmm_value/main.cc: Add test of copying custom Value.
Part of issue #1

1 files changed, 7 insertions, 0 deletions

diff --git a/tests/glibmm_value/main.cc b/tests/glibmm_value/main.cc
index a824f948..4aea37cc 100644
--- a/tests/glibmm_value/main.cc
+++ b/tests/glibmm_value/main.cc
@@ -28,6 +28,13 @@ test()
 
     const auto v = value.get();
     assert(v.bar == 1);
+
+    // Make a copy
+    Glib::Value<Foo> value2;
+    value2.init(Glib::Value<Foo>::value_type()); // TODO: Avoid this step?
+    value2 = value;
+    const auto v2 = value2.get();
+    assert(v2.bar == 1);
   }
 
   {