refactor(messages): encapsulate msg_delay logic

see also 9bbbeb60e3

src/nvim/buffer.c

@@ -1990,8 +1990,7 @@ buf_T *buflist_new(char *ffname_arg, char *sfname_arg, linenr_T lnum, int flags)
     pmap_put(int)(&buffer_handles, buf->b_fnum, buf);
     if (top_file_num < 0) {  // wrap around (may cause duplicates)
       emsg(_("W14: Warning: List of file names overflow"));
-      if (emsg_silent == 0 && !in_assert_fails && !ui_has(kUIMessages)) {
-        ui_flush();
+      if (emsg_silent == 0 && !in_assert_fails) {
         msg_delay(3001, true);  // make sure it is noticed
       }
       top_file_num = 1;

src/nvim/change.c

@@ -92,8 +92,7 @@ void change_warning(buf_T *buf, int col)
     set_vim_var_string(VV_WARNINGMSG, _(w_readonly), -1);
     msg_clr_eos();
     msg_end();
-    if (msg_silent == 0 && !silent_mode && ui_active() && !ui_has(kUIMessages)) {
-      ui_flush();
+    if (msg_silent == 0 && !silent_mode && ui_active()) {
       msg_delay(1002, true);  // give the user time to think about it
     }
     buf->b_did_warn = true;
@@ -132,7 +131,6 @@ void changed(buf_T *buf)
       // message.  Since we could be anywhere, call wait_return() now,
       // and don't let the emsg() set msg_scroll.
       if (need_wait_return && emsg_silent == 0 && !in_assert_fails && !ui_has(kUIMessages)) {
-        ui_flush();
         msg_delay(2002, true);
         wait_return(true);
         msg_scroll = save_msg_scroll;

src/nvim/fileio.c

@@ -3028,12 +3028,8 @@ int buf_check_timestamp(buf_T *buf)
         msg_clr_eos();
         msg_end();
         if (emsg_silent == 0 && !in_assert_fails && !ui_has(kUIMessages)) {
-          ui_flush();
-          // give the user some time to think about it
-          msg_delay(1004, true);
-
-          // don't redraw and erase the message
-          redraw_cmdline = false;
+          msg_delay(1004, true);  // give the user some time to think about it
+          redraw_cmdline = false;  // don't redraw and erase the message
         }
       }
       already_warned = true;

src/nvim/insexpand.c

@@ -552,10 +552,7 @@ bool check_compl_option(bool dict_opt)
     if (emsg_silent == 0 && !in_assert_fails) {
       vim_beep(kOptBoFlagComplete);
       setcursor();
-      if (!ui_has(kUIMessages)) {
-        ui_flush();
-        msg_delay(2004, false);
-      }
+      msg_delay(2004, false);
     }
     return false;
   }

src/nvim/message.c

@@ -3923,17 +3923,22 @@ int vim_dialog_yesnoallcancel(int type, char *title, char *message, int dflt)
   return VIM_CANCEL;
 }
 
-/// Force the user to see a message by pausing for `ms` milliseconds.
+/// Only for legacy UI (`!ui_has(kUIMessages)`): Pause to display a message for `ms` milliseconds.
 ///
 /// TODO(justinmk): Most of these cases may not be needed after "ui2"...
 void msg_delay(uint64_t ms, bool ignoreinput)
 {
+  if (ui_has(kUIMessages)) {
+    return;
+  }
+
   if (nvim_testing) {
     // XXX: Skip non-functional (UI only) delay in tests/CI.
     ms = 100;
   }
 
   DLOG("%" PRIu64 " ms%s", ms, nvim_testing ? " (skipped by NVIM_TEST)" : "");
+  ui_flush();
   os_delay(ms, ignoreinput);
 }
 
@@ -3944,7 +3949,6 @@ void msg_check_for_delay(bool check_msg_scroll)
 {
   if ((emsg_on_display || (check_msg_scroll && msg_scroll))
       && !did_wait_return && emsg_silent == 0 && !in_assert_fails && !ui_has(kUIMessages)) {
-    ui_flush();
     msg_delay(1006, true);
     emsg_on_display = false;
     if (check_msg_scroll) {

src/nvim/normal.c

@@ -701,7 +701,7 @@ static void normal_redraw_mode_message(NormalState *s)
   setcursor();
   ui_cursor_shape();                  // show different cursor shape
   ui_flush();
-  if (!ui_has(kUIMessages) && (msg_scroll || emsg_on_display)) {
+  if (msg_scroll || emsg_on_display) {
     msg_delay(1003, true);            // wait at least one second
   }
   if (ui_has(kUIMessages)) {

src/nvim/tag.c

@@ -742,8 +742,7 @@ void do_tag(char *tag, int type, int count, int forceit, bool verbose)
         } else {
           give_warning(IObuff, ic, true);
         }
-        if (ic && !msg_scrolled && msg_silent == 0 && !ui_has(kUIMessages)) {
-          ui_flush();
+        if (ic && !msg_scrolled && msg_silent == 0) {
           msg_delay(1007, true);
         }
       }
@@ -2981,8 +2980,7 @@ static int jumpto_tag(const char *lbuf_arg, int forceit, bool keep_help)
           // is set and match found while ignoring case.
           if (found == 2 || !save_p_ic) {
             msg(_("E435: Couldn't find tag, just guessing!"), 0);
-            if (!msg_scrolled && msg_silent == 0 && !ui_has(kUIMessages)) {
-              ui_flush();
+            if (!msg_scrolled && msg_silent == 0) {
               msg_delay(1010, true);
             }
           }