org-drill: prevent fontifcation functions from being called when saving outline

visibility info during drill sessions. This should fix slow transitions between drill
items for some people.

contrib/lisp/org-drill.el

@@ -1976,23 +1976,6 @@ visible content of the card."
       (org-drill-hide-subheadings-if 'org-drill-entry-p)))))
 
 
-;;; The following macro is necessary because `org-save-outline-visibility'
-;;; currently discards the value returned by its body and returns a garbage
-;;; value instead. (as at org mode v 7.5)
-
-(defmacro org-drill-save-visibility (&rest body)
-  "Store the current visibility state of the org buffer, and restore it
-after executing BODY. Return the value of the last expression
-in BODY."
-  (let ((retval (gensym)))
-    `(let ((,retval nil))
-       (org-save-outline-visibility t
-         (setq ,retval
-               (progn
-                 ,@body)))
-       ,retval)))
-
-
 (defun org-drill-entry ()
   "Present the current topic for interactive review, as in `org-drill'.
 Review will occur regardless of whether the topic is due for review or whether
@@ -2012,8 +1995,11 @@ See `org-drill' for more details."
   ;;  (org-back-to-heading))
   (let ((card-type (org-entry-get (point) "DRILL_CARD_TYPE"))
         (answer-fn 'org-drill-present-default-answer)
-        (cont nil))
-    (org-drill-save-visibility
+        (cont nil)
+        ;; fontification functions in `outline-view-change-hook' can cause big
+        ;; slowdowns, so we temporarily bind this variable to nil here.
+        (outline-view-change-hook nil))
+    (org-save-outline-visibility t
       (save-restriction
         (org-narrow-to-subtree)
         (org-show-subtree)
@@ -3013,4 +2999,3 @@ returns its return value."
 
 
 (provide 'org-drill)
-