gsignal: Add a new GSignalFlag to mark the first run of an accumulator function

Also add a test for signal accumulators. There was none before, and this
one now also covers the new flag.

Fixes https://gitlab.gnome.org/GNOME/glib/issues/514

gobject/tests/signals.c

@@ -185,6 +185,7 @@ struct _Test
 };
 
 static void all_types_handler (Test *test, int i, gboolean b, char c, guchar uc, guint ui, glong l, gulong ul, MyEnum e, MyFlags f, float fl, double db, char *str, GParamSpec *param, GBytes *bytes, gpointer ptr, Test *obj, GVariant *var, gint64 i64, guint64 ui64);
+static gboolean accumulator_sum (GSignalInvocationHint *ihint, GValue *return_accu, const GValue *handler_return, gpointer data);
 
 struct _TestClass
 {
@@ -238,6 +239,14 @@ test_class_init (TestClass *klass)
                 NULL,
                 G_TYPE_NONE,
                 0);
+  g_signal_new ("simple-accumulator",
+                G_TYPE_FROM_CLASS (klass),
+                G_SIGNAL_RUN_LAST,
+                0,
+                accumulator_sum, NULL,
+                NULL,
+                G_TYPE_INT,
+                0);
   g_signal_new ("generic-marshaller-1",
                 G_TYPE_FROM_CLASS (klass),
                 G_SIGNAL_RUN_LAST,
@@ -1127,6 +1136,97 @@ test_invocation_hint (void)
   g_object_unref (test);
 }
 
+static gboolean
+accumulator_sum (GSignalInvocationHint *ihint,
+                 GValue                *return_accu,
+                 const GValue          *handler_return,
+                 gpointer               data)
+{
+  gint acc = g_value_get_int (return_accu);
+  gint ret = g_value_get_int (handler_return);
+
+  g_assert_cmpint (ret, >, 0);
+
+  if (ihint->run_type & G_SIGNAL_ACCUMULATOR_FIRST_RUN)
+    {
+      g_assert_cmpint (acc, ==, 0);
+      g_assert_cmpint (ret, ==, 1);
+      g_assert_true (ihint->run_type & G_SIGNAL_RUN_FIRST);
+      g_assert_false (ihint->run_type & G_SIGNAL_RUN_LAST);
+    }
+  else if (ihint->run_type & G_SIGNAL_RUN_FIRST)
+    {
+      /* Only the first signal handler was called so far */
+      g_assert_cmpint (acc, ==, 1);
+      g_assert_cmpint (ret, ==, 2);
+      g_assert_false (ihint->run_type & G_SIGNAL_RUN_LAST);
+    }
+  else if (ihint->run_type & G_SIGNAL_RUN_LAST)
+    {
+      /* Only the first two signal handler were called so far */
+      g_assert_cmpint (acc, ==, 3);
+      g_assert_cmpint (ret, ==, 3);
+      g_assert_false (ihint->run_type & G_SIGNAL_RUN_FIRST);
+    }
+  else
+    {
+      g_assert_not_reached ();
+    }
+
+  g_value_set_int (return_accu, acc + ret);
+
+  /* Continue with the other signal handlers as long as the sum is < 6,
+   * i.e. don't run simple_accumulator_4_cb() */
+  return acc + ret < 6;
+}
+
+static gint
+simple_accumulator_1_cb (gpointer instance, gpointer data)
+{
+  return 1;
+}
+
+static gint
+simple_accumulator_2_cb (gpointer instance, gpointer data)
+{
+  return 2;
+}
+
+static gint
+simple_accumulator_3_cb (gpointer instance, gpointer data)
+{
+  return 3;
+}
+
+static gint
+simple_accumulator_4_cb (gpointer instance, gpointer data)
+{
+  return 4;
+}
+
+static void
+test_accumulator (void)
+{
+  GObject *test;
+  gint ret = -1;
+
+  test = g_object_new (test_get_type (), NULL);
+
+  /* Connect in reverse order to make sure that LAST signal handlers are
+   * called after FIRST signal handlers but signal handlers in each "group"
+   * are called in the order they were registered */
+  g_signal_connect_after (test, "simple-accumulator", G_CALLBACK (simple_accumulator_3_cb), NULL);
+  g_signal_connect_after (test, "simple-accumulator", G_CALLBACK (simple_accumulator_4_cb), NULL);
+  g_signal_connect (test, "simple-accumulator", G_CALLBACK (simple_accumulator_1_cb), NULL);
+  g_signal_connect (test, "simple-accumulator", G_CALLBACK (simple_accumulator_2_cb), NULL);
+  g_signal_emit_by_name (test, "simple-accumulator", &ret);
+
+  /* simple_accumulator_4_cb() is not run because accumulator is 6 */
+  g_assert_cmpint (ret, ==, 6);
+
+  g_object_unref (test);
+}
+
 static gboolean
 in_set (const gchar *s,
         const gchar *set[])
@@ -1153,6 +1253,7 @@ test_introspection (void)
     "simple",
     "simple-detailed",
     "simple-2",
+    "simple-accumulator",
     "generic-marshaller-1",
     "generic-marshaller-2",
     "generic-marshaller-enum-return-signed",
@@ -1578,6 +1679,7 @@ main (int argc,
   g_test_add_func ("/gobject/signals/custom-marshaller", test_custom_marshaller);
   g_test_add_func ("/gobject/signals/connect", test_connect);
   g_test_add_func ("/gobject/signals/emission-hook", test_emission_hook);
+  g_test_add_func ("/gobject/signals/accumulator", test_accumulator);
   g_test_add_func ("/gobject/signals/introspection", test_introspection);
   g_test_add_func ("/gobject/signals/block-handler", test_block_handler);
   g_test_add_func ("/gobject/signals/stop-emission", test_stop_emission);