patch 8.1.0174: after paging up and down fold line is wrongv8.1.0174

Problem:    After paging up and down fold line is wrong.
Solution:   Correct the computation of w_topline and w_botline. (Hirohito
            Higashi)

1 files changed, 16 insertions, 11 deletions

diff --git a/src/move.c b/src/move.c
index a56003013c..b2b84868ac 100644
--- a/src/move.c
+++ b/src/move.c
@@ -2457,22 +2457,27 @@ onepage(int dir, long count)
 	beginline(BL_SOL | BL_FIX);
     curwin->w_valid &= ~(VALID_WCOL|VALID_WROW|VALID_VIRTCOL);
 
-    /*
-     * Avoid the screen jumping up and down when 'scrolloff' is non-zero.
-     * But make sure we scroll at least one line (happens with mix of long
-     * wrapping lines and non-wrapping line).
-     */
-    if (retval == OK && dir == FORWARD && check_top_offset())
+    if (retval == OK && dir == FORWARD)
     {
-	scroll_cursor_top(1, FALSE);
-	if (curwin->w_topline <= old_topline
-				  && old_topline < curbuf->b_ml.ml_line_count)
+	// Avoid the screen jumping up and down when 'scrolloff' is non-zero.
+	// But make sure we scroll at least one line (happens with mix of long
+	// wrapping lines and non-wrapping line).
+	if (check_top_offset())
 	{
-	    curwin->w_topline = old_topline + 1;
+	    scroll_cursor_top(1, FALSE);
+	    if (curwin->w_topline <= old_topline
+				  && old_topline < curbuf->b_ml.ml_line_count)
+	    {
+		curwin->w_topline = old_topline + 1;
 #ifdef FEAT_FOLDING
-	    (void)hasFolding(curwin->w_topline, &curwin->w_topline, NULL);
+		(void)hasFolding(curwin->w_topline, &curwin->w_topline, NULL);
 #endif
+	    }
 	}
+#ifdef FEAT_FOLDING
+	else if (curwin->w_botline > curbuf->b_ml.ml_line_count)
+	    (void)hasFolding(curwin->w_topline, &curwin->w_topline, NULL);
+#endif
     }
 
     redraw_later(VALID);