[pango/attrlist-splice: 2/2] Reinstate previous behavior or pango_attr_list_splice

[Matthias Clasen <matthiasc src gnome org>]

commit 69f51ab0ea56184984a4520c202994465f703b04
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Jan 7 21:26:14 2022 -0500

    Reinstate previous behavior or pango_attr_list_splice
    
    If gap is zero, don't limit the inserted attributes;
    that does not make sense. Spell out the different
    use cases in the docs.
    
    Testcase included.
    
    Fixes: #607

 pango/pango-attributes.c | 20 +++++++++++++++++---
 tests/testattributes.c   | 18 ++++++++++++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)
---
diff --git a/pango/pango-attributes.c b/pango/pango-attributes.c
index c9b58b07..696f9ba1 100644
--- a/pango/pango-attributes.c
+++ b/pango/pango-attributes.c
@@ -2289,10 +2289,16 @@ pango_attr_list_update (PangoAttrList *list,
  * that applies at position @pos in @list by an amount @len,
  * and then calling [method@Pango.AttrList.change] with a copy
  * of each attribute in @other in sequence (offset in position
- * by @pos, and limited in lengh to @len).
+ * by @pos, and limited in length to @len).
  *
  * This operation proves useful for, for instance, inserting
  * a pre-edit string in the middle of an edit buffer.
+ *
+ * For backwards compatibility, the function behaves differently
+ * when @len is 0. In this case, the attributes from @other are
+ * not imited to @len, and are just overlayed on top of @list.
+ *
+ * This mode is useful for merging two lists of attributes together.
  */
 void
 pango_attr_list_splice (PangoAttrList *list,
@@ -2347,8 +2353,16 @@ pango_attr_list_splice (PangoAttrList *list,
   for (i = 0, p = other->attributes->len; i < p; i++)
     {
       PangoAttribute *attr = pango_attribute_copy (g_ptr_array_index (other->attributes, i));
-      attr->start_index = MIN (CLAMP_ADD (attr->start_index, upos), end);
-      attr->end_index = MIN (CLAMP_ADD (attr->end_index, upos), end);
+      if (ulen > 0)
+        {
+          attr->start_index = MIN (CLAMP_ADD (attr->start_index, upos), end);
+          attr->end_index = MIN (CLAMP_ADD (attr->end_index, upos), end);
+        }
+      else
+        {
+          attr->start_index = CLAMP_ADD (attr->start_index, upos);
+          attr->end_index = CLAMP_ADD (attr->end_index, upos);
+        }
 
       /* Same as above, the attribute could be squashed to zero-length; here
        * pango_attr_list_change() will take care of deleting it.
diff --git a/tests/testattributes.c b/tests/testattributes.c
index cd70edc8..d396269f 100644
--- a/tests/testattributes.c
+++ b/tests/testattributes.c
@@ -1338,6 +1338,23 @@ test_iter_epsilon_zero (void)
   g_string_free (s, TRUE);
 }
 
+static void
+test_gnumeric_splice (void)
+{
+  PangoAttrList *list, *list2;
+
+  list = pango_attr_list_from_string ("0 -1 font-desc \"Sans 10\"\n");
+  list2 = pango_attr_list_from_string ("1 2 weight bold\n");
+
+  pango_attr_list_splice (list, list2, 0, 0);
+
+  assert_attr_list (list, "0 4294967295 font-desc \"Sans 10\"\n"
+                          "1 2 weight bold\n");
+
+  pango_attr_list_unref (list);
+  pango_attr_list_unref (list2);
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -1377,6 +1394,7 @@ main (int argc, char *argv[])
   g_test_add_func ("/attributes/iter/get_font", test_iter_get_font);
   g_test_add_func ("/attributes/iter/get_attrs", test_iter_get_attrs);
   g_test_add_func ("/attributes/iter/epsilon_zero", test_iter_epsilon_zero);
+  g_test_add_func ("/attributes/gnumeric-splice", test_gnumeric_splice);
 
   return g_test_run ();
 }