'titleold': set UI title on exit #7191

closes #7129
ref #4063

src/nvim/buffer.c

@@ -3069,9 +3069,16 @@ static bool ti_change(char_u *str, char_u **last)
 /// Set current window title
 void resettitle(void)
 {
+  // if icon change, should the title be reset too?
+  if (p_icon) {
     ui_call_set_title(cstr_as_string((char *)lasttitle));
     ui_call_set_icon(cstr_as_string((char *)lasticon));
+  } else if (p_title) {
+    ui_call_set_title(cstr_as_string((char *)lasttitle));
+  }
+  if (p_title || p_icon) {
     ui_flush();
+  }
 }
 
 # if defined(EXITFREE)

src/nvim/globals.h

@@ -279,6 +279,7 @@ EXTERN int need_wait_return INIT(= 0);      /* need to wait for return later */
 EXTERN int did_wait_return INIT(= FALSE);       /* wait_return() was used and
                                                    nothing written since then */
 EXTERN int need_maketitle INIT(= TRUE);      /* call maketitle() soon */
+EXTERN int did_enable_title INIT(= FALSE);   /* did set title */
 
 EXTERN int quit_more INIT(= FALSE);         /* 'q' hit at "--more--" msg */
 #if defined(UNIX) || defined(MACOS_X)

src/nvim/option.c

@@ -1953,6 +1953,7 @@ did_set_title (
   if (starting != NO_SCREEN) {
     maketitle();
     resettitle();
+    did_enable_title = true;
   }
 }
 

src/nvim/os_unix.c

@@ -15,6 +15,7 @@
 #include <string.h>
 
 #include "nvim/api/private/handle.h"
+#include "nvim/api/private/helpers.h"
 #include "nvim/vim.h"
 #include "nvim/ascii.h"
 #include "nvim/os_unix.h"
@@ -137,6 +138,12 @@ void mch_exit(int r) FUNC_ATTR_NORETURN
 {
   exiting = true;
 
+  if ((p_title
+       || (did_enable_title
+           && (p_titlestring == NULL || STRLEN(p_titlestring) == 0)))
+      && p_titleold != NULL) {
+    ui_call_set_title(cstr_as_string((char *)p_titleold));
+  }
   ui_builtin_stop();
   ui_flush();
   ml_close_all(true);           // remove all memfiles