patch 9.0.0447: using :echowin while at the hit-enter prompt causes problems

Problem:    Using :echowin while at the hit-enter prompt causes problems.
Solution:   Do not prompt for :echowin.  Postpone showing the message window.
            Start the timer when the window is displayed.

src/ex_getln.c

@@ -3890,7 +3890,8 @@ redrawcmd(void)
     void
 compute_cmdrow(void)
 {
-    if (exmode_active || msg_scrolled != 0)
+    // ignore "msg_scrolled" in update_screen(), it will be reset soon.
+    if (exmode_active || (msg_scrolled != 0 && !updating_screen))
 	cmdline_row = Rows - 1;
     else
 	cmdline_row = W_WINROW(lastwin) + lastwin->w_height

src/message.c

@@ -1157,6 +1157,10 @@ wait_return(int redraw)
     // need_wait_return to do it later.
     if (msg_silent != 0)
 	return;
+#ifdef HAS_MESSAGE_WINDOW
+    if (in_echowindow)
+	return;
+#endif
 
     /*
      * When inside vgetc(), we can't wait for a typed character at all.

src/popupwin.c

@@ -31,6 +31,13 @@ static poppos_entry_T poppos_entries[] = {
 #ifdef HAS_MESSAGE_WINDOW
 // Window used for ":echowindow"
 static win_T *message_win = NULL;
+
+// Flag set when a message is added to the message window, timer is started
+// when the message window is drawn.  This might be after pressing Enter at the
+// hit-enter prompt.
+static int    start_message_win_timer = FALSE;
+
+static void may_start_message_win_timer(win_T *wp);
 #endif
 
 static void popup_adjust_position(win_T *wp);
@@ -4268,6 +4275,11 @@ update_popups(void (*win_update)(win_T *wp))
 
 	// Back to the normal zindex.
 	screen_zindex = 0;
+
+#ifdef HAS_MESSAGE_WINDOW
+	// if this was the message window popup may start the timer now
+	may_start_message_win_timer(wp);
+#endif
     }
 
 #if defined(FEAT_SEARCH_EXTRA)
@@ -4513,8 +4525,18 @@ popup_show_message_win(void)
 	    popup_update_color(message_win, TYPE_MESSAGE_WIN);
 	    popup_show(message_win);
 	}
+	start_message_win_timer = TRUE;
+    }
+}
+
+    static void
+may_start_message_win_timer(win_T *wp)
+{
+    if (wp == message_win && start_message_win_timer)
+    {
 	if (message_win->w_popup_timer != NULL)
 	    timer_start(message_win->w_popup_timer);
+	start_message_win_timer = FALSE;
     }
 }
 
@@ -4552,8 +4574,9 @@ end_echowindow(void)
 {
     in_echowindow = FALSE;
 
-    // show the message window now
+    if ((State & MODE_HITRETURN) == 0)
-    redraw_cmd(FALSE);
+	// show the message window now
+	redraw_cmd(FALSE);
 
     // do not overwrite messages
     // TODO: only for message window

src/screen.c

@@ -3038,18 +3038,18 @@ screenclear2(int doclear)
     screen_cleared = TRUE;	// can use contents of ScreenLines now
 
     win_rest_invalid(firstwin);	// redraw all regular windows
-#ifdef FEAT_PROP_POPUP
-    popup_redraw_all();		// redraw all popup windows
-#endif
     redraw_cmdline = TRUE;
     redraw_tabline = TRUE;
     if (must_redraw == UPD_CLEAR)	// no need to clear again
 	must_redraw = UPD_NOT_VALID;
+    msg_scrolled = 0;		// compute_cmdrow() uses this
     compute_cmdrow();
+#ifdef FEAT_PROP_POPUP
+    popup_redraw_all();		// redraw all popup windows
+#endif
     msg_row = cmdline_row;	// put cursor on last line for messages
     msg_col = 0;
     screen_start();		// don't know where cursor is now
-    msg_scrolled = 0;		// can't scroll back
     msg_didany = FALSE;
     msg_didout = FALSE;
 }

src/testdir/dumps/Test_echowindow_6.dump

@@ -0,0 +1,8 @@
+|~+0#4040ff13#ffffff0| @73
+|~| @73
+|~| @73
+|~| @73
+|o+0#0000000&|n|e| @71
+|t|w|o| @71
+|t|h|r|e@1| @69
+|P+0#00e0003&|r|e|s@1| |E|N|T|E|R| |o|r| |t|y|p|e| |c|o|m@1|a|n|d| |t|o| |c|o|n|t|i|n|u|e> +0#0000000&@35

src/testdir/dumps/Test_echowindow_7.dump

@@ -0,0 +1,8 @@
+>s+0&#ffffff0|o|m|e| |t|e|x|t| @65
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|═+0#e000002&@74
+|l|a|t|e|r| |m|e|s@1|a|g|e| @61
+| +0#0000000&@74
+@57|1|,|1| @10|A|l@1| 

src/testdir/test_messages.vim

@@ -401,6 +401,28 @@ func Test_echowindow()
           echowindow 'line' n
         endfor
       endfunc
+
+      def TwoMessages()
+        popup_clear()
+        set cmdheight=2
+        redraw
+        timer_start(100, (_) => {
+            echowin 'message'
+          })
+        echo 'one'
+        echo 'two'
+      enddef
+
+      def ThreeMessages()
+        popup_clear()
+        redraw
+        timer_start(100, (_) => {
+            echowin 'later message'
+          })
+        echo 'one'
+        echo 'two'
+        echo 'three'
+      enddef
   END
   call writefile(lines, 'XtestEchowindow')
   let buf = RunVimInTerminal('-S XtestEchowindow', #{rows: 8})
@@ -415,6 +437,16 @@ func Test_echowindow()
   call term_sendkeys(buf, ":call ManyMessages()\<CR>")
   call VerifyScreenDump(buf, 'Test_echowindow_4', {})
 
+  call term_sendkeys(buf, ":call TwoMessages()\<CR>")
+  call VerifyScreenDump(buf, 'Test_echowindow_5', {})
+
+  call term_sendkeys(buf, ":call ThreeMessages()\<CR>")
+  sleep 120m
+  call VerifyScreenDump(buf, 'Test_echowindow_6', {})
+
+  call term_sendkeys(buf, "\<CR>")
+  call VerifyScreenDump(buf, 'Test_echowindow_7', {})
+
   " clean up
   call StopVimInTerminal(buf)
   call delete('XtestEchowindow')

src/version.c

@@ -703,6 +703,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    447,
 /**/
     446,
 /**/