actor: rollback pivot translation even on explicit transforms

When setting an explicit transform with clutter_actor_set_transform()
and a non (0,0) pivot-point, clutter_actor_apply_transform() will fail
to roll back the pivot-point translation done before multiplying the
transformation matrix due to the "out:" label being slightly misplaced
in clutter_actor_real_apply_transform().

This works properly:
  clutter_actor_set_pivot_point (actor, 0.5, 0.5);
  clutter_actor_set_rotation_angle (actor, CLUTTER_Z_AXIS, 30);

This results in the actor being moved to the pivot-point position:
  clutter_actor_set_pivot_point (actor, 0.5, 0.5);
  clutter_matrix_init_identity(&matrix);
  cogl_matrix_rotate (&matrix, 30, 0, 0, 1.0);
  clutter_actor_set_transform (actor, &matrix);

This also add a conformance test checking that even when using a
pivot-point, no matter how a rotation is set the resulting
transformation matrix will be the same.

https://bugzilla.gnome.org/show_bug.cgi?id=690214

clutter/clutter-actor.c

@@ -3072,11 +3072,11 @@ clutter_actor_real_apply_transform (ClutterActor  *self,
           cogl_matrix_translate (transform, -x, -y, -z);
         }
 
+out:
       /* roll back the pivot translation */
       if (pivot_x != 0.f || pivot_y != 0.f || info->pivot_z != 0.f)
         cogl_matrix_translate (transform, -pivot_x, -pivot_y, -info->pivot_z);
 
-out:
       priv->transform_valid = TRUE;
     }
 

tests/conform/actor-invariants.c

@@ -442,3 +442,43 @@ default_stage (TestConformSimpleFixture *fixture,
 
   g_assert (CLUTTER_ACTOR_IS_REALIZED (def_stage));
 }
+
+void
+actor_pivot_transformation (TestConformSimpleFixture *fixture,
+                            gconstpointer             data)
+{
+  ClutterActor *stage, *actor_implicit, *actor_explicit;
+  ClutterMatrix transform, result_implicit, result_explicit;
+  ClutterActorBox allocation = CLUTTER_ACTOR_BOX_INIT (0, 0, 90, 30);
+  gfloat angle = 30;
+
+  stage = clutter_stage_new ();
+
+  actor_implicit = clutter_actor_new ();
+  actor_explicit = clutter_actor_new ();
+
+  clutter_actor_add_child (stage, actor_implicit);
+  clutter_actor_add_child (stage, actor_explicit);
+
+  /* Fake allocation or pivot-point will not have any effect */
+  clutter_actor_allocate (actor_implicit, &allocation, CLUTTER_ALLOCATION_NONE);
+  clutter_actor_allocate (actor_explicit, &allocation, CLUTTER_ALLOCATION_NONE);
+
+  clutter_actor_set_pivot_point (actor_implicit, 0.5, 0.5);
+  clutter_actor_set_pivot_point (actor_explicit, 0.5, 0.5);
+
+  /* Implict transformation */
+  clutter_actor_set_rotation_angle (actor_implicit, CLUTTER_Z_AXIS, angle);
+
+  /* Explict transformation */
+  clutter_matrix_init_identity(&transform);
+  cogl_matrix_rotate (&transform, angle, 0, 0, 1.0);
+  clutter_actor_set_transform (actor_explicit, &transform);
+
+  clutter_actor_get_transform (actor_implicit, &result_implicit);
+  clutter_actor_get_transform (actor_explicit, &result_explicit);
+
+  clutter_actor_destroy (stage);
+
+  g_assert (cogl_matrix_equal (&result_implicit, &result_explicit));
+}

tests/conform/test-conform-main.c

@@ -162,6 +162,7 @@ main (int argc, char **argv)
   TEST_CONFORM_SIMPLE ("/actor/invariants", clone_no_map);
   TEST_CONFORM_SIMPLE ("/actor/invariants", actor_contains);
   TEST_CONFORM_SIMPLE ("/actor/invariants", default_stage);
+  TEST_CONFORM_SIMPLE ("/actor/invariants", actor_pivot_transformation);
 
   TEST_CONFORM_SIMPLE ("/actor/opacity", opacity_label);
   TEST_CONFORM_SIMPLE ("/actor/opacity", opacity_rectangle);