Avoid infloop in redisplay with tall images

* src/xdisp.c (try_scrolling): Prevent an infloop when scrolling
down near ZV.  (Bug#20808)
Call bidi_unshelve_cache to avoid memory leaks.  Use IT_CHARPOS
instead of CHARPOS.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 7c153302803..25eed01ecfc 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -15094,11 +15094,13 @@ try_scrolling (Lisp_Object window, bool just_this_one_p,
             RESTORE_IT (&it, &it, it1data);
             move_it_by_lines (&it, 1);
             SAVE_IT (it1, it, it1data);
-          } while (line_bottom_y (&it1) - start_y < amount_to_scroll);
+          } while (IT_CHARPOS (it) < ZV
+                   && line_bottom_y (&it1) - start_y < amount_to_scroll);
+          bidi_unshelve_cache (it1data, true);
         }
 
       /* If STARTP is unchanged, move it down another screen line.  */
-      if (CHARPOS (it.current.pos) == CHARPOS (startp))
+      if (IT_CHARPOS (it) == CHARPOS (startp))
         move_it_by_lines (&it, 1);
       startp = it.current.pos;
     }