inccommand: Ignore :redraw during preview

closes #9777

src/nvim/ex_docmd.c

@@ -7807,11 +7807,12 @@ static void ex_redir(exarg_T *eap)
     redir_off = FALSE;
 }
 
-/*
+/// ":redraw": force redraw
- * ":redraw": force redraw
- */
 static void ex_redraw(exarg_T *eap)
 {
+  if (State & CMDPREVIEW) {
+    return;  // Ignore :redraw during 'inccommand' preview. #9777
+  }
   int r = RedrawingDisabled;
   int p = p_lz;
 
@@ -7840,11 +7841,12 @@ static void ex_redraw(exarg_T *eap)
   ui_flush();
 }
 
-/*
+/// ":redrawstatus": force redraw of status line(s)
- * ":redrawstatus": force redraw of status line(s)
- */
 static void ex_redrawstatus(exarg_T *eap)
 {
+  if (State & CMDPREVIEW) {
+    return;  // Ignore :redrawstatus during 'inccommand' preview. #9777
+  }
   int r = RedrawingDisabled;
   int p = p_lz;
 

test/functional/ui/inccommand_spec.lua

@@ -2607,3 +2607,30 @@ it(':substitute with inccommand during :terminal activity', function()
 
   end)
 end)
+
+it(':substitute with inccommand, timer-induced :redraw #9777', function()
+  local screen = Screen.new(30,12)
+  clear()
+  command('set cmdwinheight=3')
+  command('call timer_start(10, {-> execute("redraw")}, {"repeat":-1})')
+  command('call timer_start(10, {-> execute("redrawstatus")}, {"repeat":-1})')
+  common_setup(screen, 'split', 'foo bar baz\nbar baz fox\nbar foo baz')
+
+  feed('gg')
+  feed(':%s/foo/ZZZ')
+  sleep(20)  -- Allow some timer activity.
+  screen:expect([[
+    {12:ZZZ} bar baz                   |
+    bar baz fox                   |
+    bar {12:ZZZ} baz                   |
+    {15:~                             }|
+    {15:~                             }|
+    {15:~                             }|
+    {11:[No Name] [+]                 }|
+    |1| {12:ZZZ} bar baz               |
+    |3| bar {12:ZZZ} baz               |
+    {15:~                             }|
+    {10:[Preview]                     }|
+    :%s/foo/ZZZ^                   |
+  ]])
+end)