[gimp] Bug 796014 - Cannot open some older .xcf files made with 2.8.22 in 2.10.

[Jehan Pagès <jehanp src gnome org>]

commit 66db143502bcc9352a73b81b701e161dea72d73d
Author: Jehan <jehan girinstud io>
Date:   Fri May 11 17:56:37 2018 +0200

    Bug 796014 - Cannot open some older .xcf files made with 2.8.22 in 2.10.
    
    To avoid an infinite loop, gimp_item_linked_is_locked() was temporarily
    unlinking items before calling gimp_item_is_position_locked(). This
    worked only based on gimp_item_real_is_position_locked() code which
    called gimp_item_linked_is_locked() only when it was linked. It did not
    take into account the fact that it was an abstract method which could
    have other implementations. In particular the group layer implementation
    would call in turn gimp_item_is_position_locked() on each child layer.
    
    Basically temporarily unsetting the link was anyway a very ugly hack.
    The point is simply that we are only interested by the value of the
    `lock_position` flag for this item, without further "intelligence". For
    this, use gimp_item_get_lock_position() instead.

 app/core/gimpitem-linked.c |   15 +++++----------
 1 files changed, 5 insertions(+), 10 deletions(-)
---
diff --git a/app/core/gimpitem-linked.c b/app/core/gimpitem-linked.c
index be525e0..b0cd474 100644
--- a/app/core/gimpitem-linked.c
+++ b/app/core/gimpitem-linked.c
@@ -55,18 +55,13 @@ gimp_item_linked_is_locked (GimpItem *item)
 
   for (l = list; l && ! locked; l = g_list_next (l))
     {
-      GimpItem *item = l->data;
-
-      /*  temporarily set the item to not being linked, or we will
-       *  run into a recursion because gimp_item_is_position_locked()
-       *  call this function if the item is linked
+      /* We must not use gimp_item_is_position_locked(), especially
+       * since a child implementation may call the current function and
+       * end up in infinite loop.
+       * We are only interested in the value of `lock_position` flag.
        */
-      gimp_item_set_linked (item, FALSE, FALSE);
-
-      if (gimp_item_is_position_locked (item))
+      if (gimp_item_get_lock_position (l->data))
         locked = TRUE;
-
-      gimp_item_set_linked (item, TRUE, FALSE);
     }
 
   g_list_free (list);