# HG changeset patch
# User Bram Moolenaar <Bram@vim.org>
# Date 1648989007 -7200
# Node ID 8f92524d4556c6c0721e5f23733e204ba71222bd
# Parent  98b3cfbb2d9f78361b9a55d5cfc405776b3bb464
patch 8.2.4673: redrawing a split window is slow when using CTRL-F and CTRL-B

Commit: https://github.com/vim/vim/commit/8ef6997e2d90808dec033373c96dda68843af12e
Author: Bram Moolenaar <Bram@vim.org>
Date:   Sun Apr 3 13:23:22 2022 +0100

    patch 8.2.4673: redrawing a split window is slow when using CTRL-F and CTRL-B

    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)

diff --git a/src/screen.c b/src/screen.c
--- a/src/screen.c
+++ b/src/screen.c
@@ -3707,7 +3707,15 @@ screen_ins_lines(
      */
     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))
@@ -3879,7 +3887,7 @@ screen_del_lines(
     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
+    win_T	*wp)		// NULL or window to use width from
 {
     int		j;
     int		i;
@@ -3934,7 +3942,15 @@ screen_del_lines(
      * 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 && (
diff --git a/src/version.c b/src/version.c
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@ static char *(features[]) =
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4673,
+/**/
     4672,
 /**/
     4671,