To: vim_dev@googlegroups.com
Subject: Patch 8.2.4673
Fcc: outbox
From: Bram Moolenaar <Bram@moolenaar.net>
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------------

Patch 8.2.4673
Problem:    Redrawing a vertically split window is slow when using CTRL-F and
            CTRL-B.
Solution:   When deciding on USE_REDRAW bail out if scrolling more than three
            lines. (issue #8002)
Files:      src/screen.c


*** ../vim-8.2.4672/src/screen.c	2022-04-01 19:44:43.949807161 +0100
--- src/screen.c	2022-04-03 13:17:37.951718866 +0100
***************
*** 3707,3713 ****
--- 3707,3721 ----
       */
      result_empty = (row + line_count >= end);
      if (wp != NULL && wp->w_width != Columns && *T_CSV == NUL)
+     {
+ 	// Avoid that lines are first cleared here and then redrawn, which
+ 	// results in many characters updated twice.  This happens with CTRL-F
+ 	// in a vertically split window.  With line-by-line scrolling
+ 	// USE_REDRAW should be faster.
+ 	if (line_count > 3)
+ 	    return FAIL;
  	type = USE_REDRAW;
+     }
      else if (can_clear(T_CD) && result_empty)
  	type = USE_T_CD;
      else if (*T_CAL != NUL && (line_count > 1 || *T_AL == NUL))
***************
*** 3879,3885 ****
      int		end,
      int		force,		// even when line_count > p_ttyscroll
      int		clear_attr,	// used for clearing lines
!     win_T	*wp UNUSED)	// NULL or window to use width from
  {
      int		j;
      int		i;
--- 3887,3893 ----
      int		end,
      int		force,		// even when line_count > p_ttyscroll
      int		clear_attr,	// used for clearing lines
!     win_T	*wp)		// NULL or window to use width from
  {
      int		j;
      int		i;
***************
*** 3934,3940 ****
--- 3942,3956 ----
       * 6. redraw the characters from ScreenLines[].
       */
      if (wp != NULL && wp->w_width != Columns && *T_CSV == NUL)
+     {
+ 	// Avoid that lines are first cleared here and then redrawn, which
+ 	// results in many characters updated twice.  This happens with CTRL-F
+ 	// in a vertically split window.  With line-by-line scrolling
+ 	// USE_REDRAW should be faster.
+ 	if (line_count > 3)
+ 	    return FAIL;
  	type = USE_REDRAW;
+     }
      else if (can_clear(T_CD) && result_empty)
  	type = USE_T_CD;
      else if (row == 0 && (
*** ../vim-8.2.4672/src/version.c	2022-04-03 12:59:29.358392492 +0100
--- src/version.c	2022-04-03 13:20:36.755190970 +0100
***************
*** 752,753 ****
--- 752,755 ----
  {   /* Add new patch number below this line */
+ /**/
+     4673,
  /**/

-- 
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ANIMATOR:   Aaaaagh!
VOICE OVER: The cartoon peril was no more ... The Quest for Holy Grail could
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 /// Bram Moolenaar -- Bram@Moolenaar.net -- http://www.Moolenaar.net   \\\
///                                                                      \\\
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