undrflow.c

/* gcc -o undrflow undrflow.c `pkg-config --cflags --libs gobject-2.0` */

#include <glib-object.h>

#define PROP_FOO 1
#define TEST_TYPE_FOO test_foo_get_type ()
G_DECLARE_FINAL_TYPE (TestFoo, test_foo, TEST, FOO, GObject);

struct _TestFoo
{
  GObject parent;
  unsigned foo;
};

G_DEFINE_TYPE(TestFoo, test_foo, G_TYPE_OBJECT);

static void
test_foo_get_property (GObject *object, unsigned id, GValue *value,
                       GParamSpec *pspec)
{
  if (id == PROP_FOO)
    g_value_set_uint (value, TEST_FOO (object)->foo);
  else
    G_OBJECT_WARN_INVALID_PROPERTY_ID (object, id, pspec);
}

static void
test_foo_set_property (GObject *object, unsigned id, const GValue *value,
                       GParamSpec *pspec)
{
  if (id == PROP_FOO)
    TEST_FOO (object)->foo = g_value_get_uint (value);
  else
    G_OBJECT_WARN_INVALID_PROPERTY_ID (object, id, pspec);
}

static void
test_foo_class_init (TestFooClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);

  object_class->get_property = test_foo_get_property;
  object_class->set_property = test_foo_set_property;

  g_object_class_install_property (object_class, PROP_FOO,
    g_param_spec_uint ("foo", "Foo", "Foo", 0, G_MAXUINT32, 0,
      G_PARAM_READWRITE | G_PARAM_CONSTRUCT | G_PARAM_STATIC_STRINGS));
}

static void test_foo_init (TestFoo *self) {}

int
main (int argc, char **argv)
{
  unsigned fooval;
  TestFoo* foo = g_object_new(TEST_TYPE_FOO, "foo", -1, NULL);
  g_object_get(foo, "foo", &fooval, NULL);
  g_printerr("%u ", fooval);
  g_object_set(foo, "foo", -2, NULL);
  g_object_get(foo, "foo", &fooval, NULL);
  g_printerr("%u\n", fooval);
  return 0;
}