=== modified file 'src/dispnew.c'
--- src/dispnew.c	2013-01-23 20:07:28 +0000
+++ src/dispnew.c	2013-01-25 10:49:31 +0000
@@ -107,12 +107,6 @@
 static void adjust_frame_glyphs_for_window_redisplay (struct frame *);
 static void adjust_frame_glyphs_for_frame_redisplay (struct frame *);
 
-
-/* Redisplay preemption timers.  */
-
-static EMACS_TIME preemption_period;
-static EMACS_TIME preemption_next_check;
-
 /* True upon entry to redisplay means do not assume anything about
    current contents of actual terminal frame; clear and redraw it.  */
 
@@ -122,9 +116,8 @@
 
 bool display_completed;
 
-Lisp_Object Qdisplay_table, Qredisplay_dont_pause;
+Lisp_Object Qdisplay_table;
 
-
 /* The currently selected frame.  In a single-frame version, this
    variable always equals the_only_frame.  */
 
@@ -3078,23 +3071,10 @@
   bool paused_p;
   struct window *root_window = XWINDOW (f->root_window);
 
-  if (redisplay_dont_pause)
-    force_p = 1;
-  else if (NILP (Vredisplay_preemption_period))
-    force_p = 1;
-  else if (!force_p && NUMBERP (Vredisplay_preemption_period))
+  if (!force_p && detect_input_pending_ignore_squeezables ())
     {
-      double p = XFLOATINT (Vredisplay_preemption_period);
-
-      if (detect_input_pending_ignore_squeezables ())
-	{
-	  paused_p = 1;
-	  goto do_pause;
-	}
-
-      preemption_period = EMACS_TIME_FROM_DOUBLE (p);
-      preemption_next_check = add_emacs_time (current_emacs_time (),
-					      preemption_period);
+      paused_p = 1;
+      goto do_pause;
     }
 
   if (FRAME_WINDOW_P (f))
@@ -3230,18 +3210,6 @@
       /* Record that this is not a frame-based redisplay.  */
       set_frame_matrix_frame (NULL);
 
-      if (redisplay_dont_pause)
-	force_p = 1;
-      else if (NILP (Vredisplay_preemption_period))
-	force_p = 1;
-      else if (!force_p && NUMBERP (Vredisplay_preemption_period))
-	{
-	  double p = XFLOATINT (Vredisplay_preemption_period);
-	  preemption_period = EMACS_TIME_FROM_DOUBLE (p);
-	  preemption_next_check = add_emacs_time (current_emacs_time (),
-						  preemption_period);
-	}
-
       /* Update W.  */
       update_begin (f);
       update_window (w, force_p);
@@ -3394,9 +3362,7 @@
 {
   struct glyph_matrix *desired_matrix = w->desired_matrix;
   bool paused_p;
-#if !PERIODIC_PREEMPTION_CHECKING
   int preempt_count = baud_rate / 2400 + 1;
-#endif
   struct redisplay_interface *rif = FRAME_RIF (XFRAME (WINDOW_FRAME (w)));
 #ifdef GLYPH_DEBUG
   /* Check that W's frame doesn't have glyph matrices.  */
@@ -3404,10 +3370,8 @@
 #endif
 
   /* Check pending input the first time so that we can quickly return.  */
-#if !PERIODIC_PREEMPTION_CHECKING
   if (!force_p)
     detect_input_pending_ignore_squeezables ();
-#endif
 
   /* If forced to complete the update, or if no input is pending, do
      the update.  */
@@ -3418,9 +3382,7 @@
       struct glyph_row *header_line_row;
       int yb;
       bool changed_p = 0, mouse_face_overwritten_p = 0;
-#if ! PERIODIC_PREEMPTION_CHECKING
       int n_updated = 0;
-#endif
 
       rif->update_window_begin_hook (w);
       yb = window_text_bottom_y (w);
@@ -3484,22 +3446,8 @@
 	       detect_input_pending.  If it's done too often,
 	       scrolling large windows with repeated scroll-up
 	       commands will too quickly pause redisplay.  */
-#if PERIODIC_PREEMPTION_CHECKING
-	    if (!force_p)
-	      {
-		EMACS_TIME tm = current_emacs_time ();
-		if (EMACS_TIME_LT (preemption_next_check, tm))
-		  {
-		    preemption_next_check = add_emacs_time (tm,
-							    preemption_period);
-		    if (detect_input_pending_ignore_squeezables ())
-		      break;
-		  }
-	      }
-#else
 	    if (!force_p && ++n_updated % preempt_count == 0)
 	      detect_input_pending_ignore_squeezables ();
-#endif
 	    changed_p |= update_window_line (w, vpos,
 					     &mouse_face_overwritten_p);
 
@@ -4531,13 +4479,11 @@
   if (preempt_count <= 0)
     preempt_count = 1;
 
-#if !PERIODIC_PREEMPTION_CHECKING
   if (!force_p && detect_input_pending_ignore_squeezables ())
     {
       pause_p = 1;
       goto do_pause;
     }
-#endif
 
   /* If we cannot insert/delete lines, it's no use trying it.  */
   if (!FRAME_LINE_INS_DEL_OK (f))
@@ -4578,21 +4524,8 @@
 		}
 	    }
 
-#if PERIODIC_PREEMPTION_CHECKING
-	  if (!force_p)
-	    {
-	      EMACS_TIME tm = current_emacs_time ();
-	      if (EMACS_TIME_LT (preemption_next_check, tm))
-		{
-		  preemption_next_check = add_emacs_time (tm, preemption_period);
-		  if (detect_input_pending_ignore_squeezables ())
-		    break;
-		}
-	    }
-#else
 	  if (!force_p && (i - 1) % preempt_count == 0)
 	    detect_input_pending_ignore_squeezables ();
-#endif
 
 	  update_frame_line (f, i);
 	}
@@ -4698,9 +4631,7 @@
 	}
     }
 
-#if !PERIODIC_PREEMPTION_CHECKING
  do_pause:
-#endif
 
   clear_desired_matrices (f);
   return pause_p;
@@ -5893,33 +5824,19 @@
 
 DEFUN ("redisplay", Fredisplay, Sredisplay, 0, 1, 0,
        doc: /* Perform redisplay.
-Optional arg FORCE, if non-nil, prevents redisplay from being
-preempted by arriving input, even if `redisplay-dont-pause' is nil.
-If `redisplay-dont-pause' is non-nil (the default), redisplay is never
-preempted by arriving input, so FORCE does nothing.
+Optional arg FORCE does nothing and used for backward compatibility.
 
 Return t if redisplay was performed, nil if redisplay was preempted
 immediately by pending input.  */)
   (Lisp_Object force)
 {
-  ptrdiff_t count;
-
   swallow_events (1);
-  if ((detect_input_pending_run_timers (1)
-       && NILP (force) && !redisplay_dont_pause)
-      || !NILP (Vexecuting_kbd_macro))
+  if (detect_input_pending_run_timers (1) || !NILP (Vexecuting_kbd_macro))
     return Qnil;
-
-  count = SPECPDL_INDEX ();
-  if (!NILP (force) && !redisplay_dont_pause)
-    specbind (Qredisplay_dont_pause, Qt);
   redisplay_preserve_echo_area (2);
-  unbind_to (count, Qnil);
   return Qt;
 }
 
-
-
 /***********************************************************************
 			 Other Lisp Functions
  ***********************************************************************/
@@ -6335,7 +6252,6 @@
   staticpro (&frame_and_buffer_state);
 
   DEFSYM (Qdisplay_table, "display-table");
-  DEFSYM (Qredisplay_dont_pause, "redisplay-dont-pause");
 
   DEFVAR_INT ("baud-rate", baud_rate,
 	      doc: /* The output baud rate of the terminal.
@@ -6406,19 +6322,6 @@
 See `buffer-display-table' for more information.  */);
   Vstandard_display_table = Qnil;
 
-  DEFVAR_BOOL ("redisplay-dont-pause", redisplay_dont_pause,
-	       doc: /* Non-nil means display update isn't paused when input is detected.  */);
-  redisplay_dont_pause = 1;
-
-#if PERIODIC_PREEMPTION_CHECKING
-  DEFVAR_LISP ("redisplay-preemption-period", Vredisplay_preemption_period,
-	       doc: /* Period in seconds between checking for input during redisplay.
-This has an effect only if `redisplay-dont-pause' is nil; in that
-case, arriving input preempts redisplay until the input is processed.
-If the value is nil, redisplay is never preempted.  */);
-  Vredisplay_preemption_period = make_float (0.10);
-#endif
-
 #ifdef CANNOT_DUMP
   if (noninteractive)
 #endif

=== modified file 'src/xdisp.c'
--- src/xdisp.c	2013-01-24 05:41:28 +0000
+++ src/xdisp.c	2013-01-25 10:51:24 +0000
@@ -10697,14 +10697,9 @@
 	         needs to run hooks.  */
 	      && !NILP (Vrun_hooks))
 	    {
-	      /* Must update other windows.  Likewise as in other
-		 cases, don't let this update be interrupted by
-		 pending input.  */
-	      ptrdiff_t count = SPECPDL_INDEX ();
-	      specbind (Qredisplay_dont_pause, Qt);
+	      /* Must update other windows.  */
 	      windows_or_buffers_changed = 1;
 	      redisplay_internal ();
-	      unbind_to (count, Qnil);
 	    }
 	  else if (FRAME_WINDOW_P (f) && n == 0)
 	    {