Fix lost C-g events in NS port under loaddancol/quit-improvements2

The NS port was incorrectly reading input events in ns_flush_display,
storing them in a local variable that was never processed.  This caused
C-g (quit) events to be lost when Emacs was under heavy load, making it
difficult to interrupt long-running operations.

* src/nsterm.m (ns_flush_display): Pass NULL instead of a local
variable to ns_read_socket_1, ensuring events are processed normally
instead of being discarded.
* etc/NEWS: Announce the fix.

2 files changed, 9 insertions, 4 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 90b9c7ea9a2..b1f349cc3e5 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -2002,6 +2002,11 @@ determined by the new user option 'pulse-face-duration'.
 ** Miscellaneous
 
 ---
+*** Fixed lost C-g events on NS port under heavy load.
+The NS port now no longer loses quits when redisplay happens frequently,
+for example, during certain kinds of heavy IO load.
+
+---
 *** 'tooltip-mode' now shows tooltips after delay on TTY frames.
 Display of tooltips on text-only terminals now happens after
 'tooltip-delay' as it does on GUI terminals.  To get back the old
diff --git a/src/nsterm.m b/src/nsterm.m
index 003aadb9782..59728aa11b0 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -5487,10 +5487,10 @@ ns_update_window_end (struct window *w, bool cursor_on_p,
 static void
 ns_flush_display (struct frame *f)
 {
-  struct input_event ie;
-
-  EVENT_INIT (ie);
-  ns_read_socket_1 (FRAME_TERMINAL (f), &ie, YES);
+  /* Must pass NULL for hold_quit: otherwise,
+     we lose quits under load because we discard what ends
+     up in hold_quit.  */
+  ns_read_socket_1 (FRAME_TERMINAL (f), NULL, YES);
 }
 
 /* This and next define (many of the) public functions in this