commit a338adcf222b6a24e26ea5ae6a2ad27f914acb38
author Bram Moolenaar <Bram@vim.org> Wed Jan 31 20:51:47 2018 +0100
committer Bram Moolenaar <Bram@vim.org> Wed Jan 31 20:51:47 2018 +0100
tree 0ffe28d0a3a60c2c1444a991514505c448d4335b
parent 37badc898b8d167e11553b6d05908ffd35928a6e

patch 8.0.1449: slow redrawing with DirectX

Problem:    Slow redrawing with DirectX.
Solution:   Avoid calling gui_mch_flush() unnecessarily, especially when
            updating the cursor. (Ken Takata, closes #2560)

src/message.c

diff --git a/src/message.c b/src/message.c
index c40b6cf..2114033 100644
--- a/src/message.c
+++ b/src/message.c
@@ -2316,7 +2316,9 @@
 	gui_undraw_cursor();
 #endif
     /* scrolling up always works */
+    mch_disable_flush();
     screen_del_lines(0, 0, 1, (int)Rows, TRUE, 0, NULL);
+    mch_enable_flush();
 
     if (!can_clear((char_u *)" "))
     {