patch 8.1.0856: when scrolling a window the cursorline is not always updated

Problem:    When scrolling a window other than the current one the cursorline
            highlighting is not always updated. (Jason Franklin)
Solution:   Call redraw_for_cursorline() after scrolling.  Only set
            w_last_cursorline when drawing the cursor line.  Reset the lines
            to be redrawn also when redrawing the whole window.

src/move.c

@@ -19,7 +19,6 @@
 
 #include "vim.h"
 
-static void redraw_for_cursorline(win_T *wp);
 static int scrolljump_value(void);
 static int check_top_offset(void);
 static void curs_rows(win_T *wp);
@@ -128,7 +127,7 @@ reset_cursorline(void)
  * Redraw when w_cline_row changes and 'relativenumber' or 'cursorline' is
  * set.
  */
-    static void
+    void
 redraw_for_cursorline(win_T *wp)
 {
     if ((wp->w_p_rnu
@@ -158,7 +157,6 @@ redraw_for_cursorline(win_T *wp)
 	    }
 	    else
 		redraw_win_later(wp, SOME_VALID);
-	    wp->w_last_cursorline = wp->w_cursor.lnum;
 	}
 #endif
     }

src/normal.c

@@ -4587,6 +4587,10 @@ nv_mousescroll(cmdarg_T *cap)
 	}
     }
 # endif
+# ifdef FEAT_SYN_HL
+    if (curwin != old_curwin && curwin->w_p_cul)
+	redraw_for_cursorline(curwin);
+# endif
 
     curwin->w_redr_status = TRUE;
 

src/proto/move.pro

@@ -1,5 +1,6 @@
 /* move.c */
 void reset_cursorline(void);
+void redraw_for_cursorline(win_T *wp);
 void update_topline_redraw(void);
 void update_topline(void);
 void update_curswant(void);

src/version.c

@@ -783,6 +783,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    856,
 /**/
     855,
 /**/