(update_interval): Properly update `position' field of used intervals.

1 files changed, 17 insertions, 7 deletions

diff --git a/src/intervals.c b/src/intervals.c
index f52e6ea4727..c5dad670926 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -672,7 +672,8 @@ previous_interval (interval)
 }
 
 /* Find the interval containing POS given some non-NULL INTERVAL
-   in the same tree. */
+   in the same tree.  Note that we need to update interval->position
+   if we go down the tree.  */
 INTERVAL
 update_interval (i, pos)
      register INTERVAL i;
@@ -686,22 +687,31 @@ update_interval (i, pos)
       if (pos < i->position) 
         {
           /* Move left. */
-          if (pos >= i->position - TOTAL_LENGTH (i->left))
-            i = i->left;                /* Move to the left child */
+          if (pos >= i->position - TOTAL_LENGTH (i->left)) 
+            {
+              i->left->position = i->position - TOTAL_LENGTH (i->left)
+                + LEFT_TOTAL_LENGTH (i->left);
+              i = i->left;              /* Move to the left child */
+            }
           else if (NULL_PARENT (i)) 
             error ("Point before start of properties");
-          else  i = i->parent;
+          else  
+              i = i->parent;
           continue;
         }
       else if (pos >= INTERVAL_LAST_POS (i))
         {
           /* Move right. */
-          if (pos < INTERVAL_LAST_POS (i) + TOTAL_LENGTH (i->right))
-            i = i->right;               /* Move to the right child */
+          if (pos < INTERVAL_LAST_POS (i) + TOTAL_LENGTH (i->right)) 
+            {
+              i->right->position = INTERVAL_LAST_POS (i) +
+                LEFT_TOTAL_LENGTH (i->right);
+              i = i->right;             /* Move to the right child */
+            }
           else if (NULL_PARENT (i)) 
             error ("Point after end of properties");
           else 
-            i = i->parent;
+              i = i->parent;
           continue;
         }
       else