Fix support for macOS multi-tty in Emacs 27.1

multi-tty.patch

diff --git a/lisp/server.el b/lisp/server.el
index 5efba17a01..c194d78ad1 100644
--- a/lisp/server.el
+++ b/lisp/server.el
@@ -1182,10 +1182,9 @@ The following commands are accepted by the client:
                  ;; choice there.)  In daemon mode on Windows, we can't
                  ;; make tty frames, so force the frame type to GUI
                  ;; there too.
-                 (when (or (and (eq system-type 'windows-nt)
-                                (or (daemonp)
-                                    (eq window-system 'w32)))
-                           (eq window-system 'mac))
+                   (when (and (eq system-type 'windows-nt)
+                              (or (daemonp)
+                              (eq window-system 'w32)))
                    (push "-window-system" args-left)))
 
                 ;; -position +LINE[:COLUMN]:  Set point to the given
diff --git a/src/frame.c b/src/frame.c
index 843312ab78..d68081002f 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -1267,12 +1267,8 @@ affects all frames on the same terminal device.  */)
     emacs_abort ();
 #else /* not MSDOS */
 
-#if defined WINDOWSNT || defined HAVE_MACGUI /* This should work now! */
-  if (sf->output_method != output_termcap
-#ifdef HAVE_MACGUI
-      && sf->output_method != output_initial
-#endif
-      )
+#ifdef WINDOWS_NT /* This should work now */
+  if (sf->output_method != output_termcap)
     error ("Not using an ASCII terminal now; cannot make a new ASCII frame");
 #endif
 #endif /* not MSDOS */
diff --git a/src/macterm.c b/src/macterm.c
index ce7c96e29c..69ec3c7a1a 100644
--- a/src/macterm.c
+++ b/src/macterm.c
@@ -2946,6 +2946,7 @@ mac_mouse_position (struct frame **fp, int insist, Lisp_Object *bar_window,
 {
   struct frame *f1;
   struct mac_display_info *dpyinfo = FRAME_DISPLAY_INFO (*fp);
+  struct frame *sf = SELECTED_FRAME ();
 
   block_input ();
 
@@ -2966,7 +2967,7 @@ mac_mouse_position (struct frame **fp, int insist, Lisp_Object *bar_window,
     else
       f1 = XFRAME (mac_event_frame ());
 
-    if (f1)
+    if (f1 && sf->output_method != output_termcap)
       {
 	/* Ok, we found a frame.  Store all the values.
 	   last_mouse_glyph is a rectangle used to reduce the

Details in https://goykhman.ca/gene/blog/2020/2020-12-06-emacs-27-multi-tty-patch.html