(redisplay_window): Clear force_start field

before running the Qwindow_scroll_functions.
In the recenter case, set w->start before running them.

1 files changed, 8 insertions, 1 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index fbffc857128..4f236b7fa7f 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -1502,11 +1502,16 @@ redisplay_window (window, just_this_one)
      unless the specified location is outside the accessible range.  */
   if (!NILP (w->force_start))
     {
+      w->force_start = Qnil;
       /* Forget any recorded base line for line number display.  */
       w->base_line_number = Qnil;
       /* Redisplay the mode line.  Select the buffer properly for that.
          Also, run the hook window-scroll-functions
          because we have scrolled.  */
+      /* Note, we do this after clearing force_start because
+         if there's an error, it is better to forget about force_start
+         than to get into an infinite loop calling the hook functions
+         and having them get more errors.  */
       if (!update_mode_line
           || ! NILP (Vwindow_scroll_functions))
         {
@@ -1520,7 +1525,6 @@ redisplay_window (window, just_this_one)
             run_hook_with_args_2 (Qwindow_scroll_functions, window,
                                   make_number (startp));
         }
-      w->force_start = Qnil;
       XSETFASTINT (w->last_modified, 0);
       if (startp < BEGV) startp = BEGV;
       if (startp > ZV)   startp = ZV;
@@ -1718,6 +1722,9 @@ recenter:
   w->base_line_number = Qnil;
 
   pos = *vmotion (PT, - (height / 2), w);
+  /* Set startp here explicitly in case that helps avoid an infinite loop
+     in case the window-scroll-functions functions get errors.  */
+  Fset_marker (w->start, make_number (pos), Qnil);
   if (! NILP (Vwindow_scroll_functions))
     run_hook_with_args_2 (Qwindow_scroll_functions, window,
                           make_number (pos.bufpos));