avoid flashing of popupmnu patch for Neovim

edit.c.diff

diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index 9d07878f..436d628c 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -2406,7 +2406,6 @@ static void ins_compl_upd_pum(void)
 
   if (compl_match_array != NULL) {
     h = curwin->w_cline_height;
-    update_screen(0);
     if (h != curwin->w_cline_height)
       ins_compl_del_pum();
   }
@@ -2476,9 +2475,6 @@ void ins_compl_show_pum(void)
   /* Dirty hard-coded hack: remove any matchparen highlighting. */
   do_cmdline_cmd("if exists('g:loaded_matchparen')|3match none|endif");
 
-  /* Update the screen before drawing the popup menu over it. */
-  update_screen(0);
-
   if (compl_match_array == NULL) {
     array_changed = true;
     // Need to build the popup menu list.
@@ -2580,6 +2576,9 @@ void ins_compl_show_pum(void)
   // part of the screen would be updated.  We do need to redraw here.
   dollar_vcol = -1;
 
+  /* Update the screen before drawing the popup menu over it. */
+  update_screen(0);
+
   // Compute the screen column of the start of the completed text.
   // Use the cursor to get all wrapping and other settings right.
   col = curwin->w_cursor.col;

popupmnu.c.diff

diff --git a/src/nvim/popupmnu.c b/src/nvim/popupmnu.c
index 947814de..f48c40d4 100644
--- a/src/nvim/popupmnu.c
+++ b/src/nvim/popupmnu.c
@@ -660,7 +660,7 @@ static int pum_set_selected(int n, int repeat)
 
             // Return cursor to where we were
             validate_cursor();
-            redraw_later(SOME_VALID);
+            redraw_win_later(curwin, REDRAW_TOP);
 
             // When the preview window was resized we need to
             // update the view on the buffer.  Only go back to
@@ -676,7 +676,7 @@ static int pum_set_selected(int n, int repeat)
             // Update the screen before drawing the popup menu.
             // Enable updating the status lines.
             pum_is_visible = false;
-            update_screen(0);
+            win_redr_status(curwin);
             pum_is_visible = true;
 
             if (!resized && win_valid(curwin_save)) {
@@ -688,7 +688,7 @@ static int pum_set_selected(int n, int repeat)
             // May need to update the screen again when there are
             // autocommands involved.
             pum_is_visible = false;
-            update_screen(0);
+            win_redr_status(curwin);
             pum_is_visible = true;
           }
         }

The original patch for vim(not merged) is:

• https://gist.github.com/mattn/8af649c404ce7253398d
• https://gist.github.com/mattn/6240679

By @mattn.