GSequence: Make g_sequence_iter_move behave as documented

As pointed out in bug 658313, moving before the begin iter is
supposed to return the begin iter, not the end iter. Also add
a test for this behaviour.

glib/gsequence.c

@@ -1422,12 +1422,18 @@ g_sequence_iter_move (GSequenceIter *iter,
                       gint           delta)
 {
   gint new_pos;
+  gint len;
 
   g_return_val_if_fail (iter != NULL, NULL);
 
+  len = g_sequence_get_length (get_sequence (iter));
+
   new_pos = node_get_pos (iter) + delta;
 
-  new_pos = clamp_position (get_sequence (iter), new_pos);
+  if (new_pos < 0)
+    new_pos = 0;
+  else if (new_pos > len)
+    new_pos = len;
 
   return node_get_by_pos (iter, new_pos);
 }

glib/tests/sequence.c

@@ -1210,6 +1210,35 @@ test_out_of_range_jump (void)
 
   g_assert (g_sequence_iter_is_begin (iter));
   g_assert (g_sequence_iter_is_end (iter));
+
+  g_sequence_free (seq);
+}
+
+static void
+test_iter_move (void)
+{
+  GSequence *seq = g_sequence_new (NULL);
+  GSequenceIter *iter;
+  gint i;
+
+  for (i = 0; i < 10; ++i)
+    g_sequence_append (seq, GINT_TO_POINTER (i));
+
+  iter = g_sequence_get_begin_iter (seq);
+  iter = g_sequence_iter_move (iter, 5);
+  g_assert_cmpint (GPOINTER_TO_INT (g_sequence_get (iter)), ==, 5);
+
+  iter = g_sequence_iter_move (iter, -10);
+  g_assert (g_sequence_iter_is_begin (iter));
+
+  iter = g_sequence_get_end_iter (seq);
+  iter = g_sequence_iter_move (iter, -5);
+  g_assert_cmpint (GPOINTER_TO_INT (g_sequence_get (iter)), ==, 5);
+
+  iter = g_sequence_iter_move (iter, 10);
+  g_assert (g_sequence_iter_is_end (iter));
+
+  g_sequence_free (seq);
 }
 
 static int
@@ -1326,6 +1355,8 @@ test_stable_sort (void)
       iter = g_sequence_iter_next (iter);
       g_sequence_check (seq);
     }
+
+  g_sequence_free (seq);
 }
 
 int
@@ -1340,6 +1371,7 @@ main (int argc,
 
   /* Standalone tests */
   g_test_add_func ("/sequence/out-of-range-jump", test_out_of_range_jump);
+  g_test_add_func ("/sequence/iter-move", test_iter_move);
   g_test_add_func ("/sequence/insert-sorted-non-pointer", test_insert_sorted_non_pointer);
   g_test_add_func ("/sequence/stable-sort", test_stable_sort);