Send kitty keyboard probe only if extended-keys is not off.

CHANGES

@@ -115,8 +115,8 @@ CHANGES FROM 3.7c TO 3.8
 * Change show-options and show-hooks to use formats and add a -F flag to each.
 
 * Add support for the Kitty keyboard protocol. When extended-keys is on,
-  tmux uses it with terminals which support it, detected when a client
+  tmux uses it with terminals which support it, detected by querying the
-  attaches or set with a new kittykeys terminal feature, and standard
+  terminal or set with a new kittykeys terminal feature, and standard
   extended keys or VT10x keys with other terminals, so terminals with
   different capabilities may be attached at the same time. Programs inside
   tmux may ask for either the Kitty protocol or modifyOtherKeys and get keys

options.c

@@ -1401,10 +1401,8 @@ options_push_changes(const char *name)
 			server_client_set_key_table(loop, NULL);
 	}
 	if (strcmp(name, "extended-keys") == 0) {
-		TAILQ_FOREACH(loop, &clients, entry) {
+		TAILQ_FOREACH(loop, &clients, entry)
-			if (loop->tty.flags & TTY_STARTED)
+			tty_extended_keys_changed(&loop->tty);
-				tty_update_features(&loop->tty);
-		}
 	}
 	if (strcmp(name, "user-keys") == 0) {
 		TAILQ_FOREACH(loop, &clients, entry) {

regress/kitty-keys-clients.sh

@@ -10,7 +10,7 @@ KCONF=$(mktemp)
 LCONF=$(mktemp)
 OUT=$(mktemp)
 TMP=$(mktemp)
-SOCKETS="testKmc$$ testKka$$ testKua$$ testKrt$$ testKru$$ testKlq$$ testKlu$$"
+SOCKETS="testKmc$$ testKka$$ testKua$$ testKrt$$ testKru$$ testKlq$$ testKlu$$ testKpo$$ testKpi$$"
 
 printf '%s\n' 'set -g extended-keys on' >"$KCONF"
 printf '%s\n' 'set -g extended-keys off' >"$LCONF"
@@ -142,5 +142,22 @@ wait_for_client_mode "$LQ" '' 'VT10x' || exit 1
 $LU send-keys C-a
 wait_for_output "$TMP" || exit 1
 [ "$(tr -d ' \n' <"$TMP")" = '1b5b39373b3575' ] || exit 1
+$LU kill-server 2>/dev/null
+$LQ kill-server 2>/dev/null
+
+# The Kitty query must not be sent while extended-keys is off, but must be sent
+# and answered once it is turned on.
+: >"$OUT"
+PO="$TEST_TMUX -LtestKpo$$ -f$KCONF"
+PI="$TEST_TMUX -LtestKpi$$ -f$LCONF"
+$PI new-session -d -x80 -y24 -s q || exit 1
+$PO new-session -d -x80 -y24 "sleep 1; $PI attach-session -t q" || exit 1
+$PO pipe-pane -O -t: "cat >>'$OUT'"
+wait_for_client_mode "$PI" '' 'VT10x' || exit 1
+sleep 1
+od -An -v -t x1 <"$OUT" | tr -d ' \n' | grep -q 1b5b3f75 && exit 1
+$PI set-option -g extended-keys on
+wait_for_client_mode "$PI" '' 'Kitty 1' || exit 1
+od -An -v -t x1 <"$OUT" | tr -d ' \n' | grep -q 1b5b3f75 || exit 1
 
 exit 0

tmux.1

@@ -4955,7 +4955,8 @@ this feature is disabled and only standard keys are reported.
 .Pp
 .Nm
 will always request extended keys itself if the terminal supports them.
-Support for the Kitty keyboard protocol is detected when a client attaches.
+When enabled, support for the Kitty keyboard protocol is detected by asking the
+terminal when a client attaches or the option is changed.
 See also the
 .Ic kittykeys
 and

tmux.h

@@ -3037,6 +3037,7 @@ void	tty_invalidate(struct tty *);
 void	tty_start_tty(struct tty *);
 void	tty_send_requests(struct tty *);
 void	tty_repeat_requests(struct tty *, int);
+void	tty_extended_keys_changed(struct tty *);
 void	tty_stop_tty(struct tty *);
 void	tty_set_title(struct tty *, const char *);
 void	tty_set_path(struct tty *, const char *);

tty-keys.c

@@ -1562,7 +1562,7 @@ tty_keys_device_attributes(struct tty *tty, const char *buf, size_t len,
 	}
 	log_debug("%s: received primary DA %.*s", c->name, (int)*size, buf);
 
-	/* A DA response without a preceding keyboard response means no support. */
+	/* The keyboard query, if sent, is answered first; else nothing is due. */
 	tty->flags |= TTY_HAVEKKB;
 	tty_update_features(tty);
 	tty->flags |= TTY_HAVEDA;

tty.c

@@ -404,11 +404,14 @@ tty_start_tty(struct tty *tty)
 void
 tty_send_requests(struct tty *tty)
 {
+	int	ek;
+
 	if (~tty->flags & TTY_STARTED)
 		return;
 
 	if (tty->term->flags & TERM_VT100LIKE) {
-		if (~tty->flags & TTY_HAVEKKB)
+		ek = options_get_number(global_options, "extended-keys");
+		if (ek != 0 && (~tty->flags & TTY_HAVEKKB))
 			tty_puts(tty, "\033[?u");
 		if (~tty->flags & TTY_HAVEDA)
 			tty_puts(tty, "\033[c");
@@ -451,6 +454,25 @@ tty_repeat_requests(struct tty *tty, int force)
 	tty_start_start_timer(tty);
 }
 
+/* Ask about Kitty keyboard support if extended-keys was turned on later. */
+void
+tty_extended_keys_changed(struct tty *tty)
+{
+	if (~tty->flags & TTY_STARTED)
+		return;
+	tty_update_features(tty);
+
+	if (options_get_number(global_options, "extended-keys") == 0)
+		return;
+	if (~tty->term->flags & TERM_VT100LIKE)
+		return;
+	if (tty->term->flags & TERM_KITTYKEYS)
+		return;
+	tty->flags &= ~TTY_HAVEKKB;
+	tty_puts(tty, "\033[?u");
+	tty_start_start_timer(tty);
+}
+
 void
 tty_stop_tty(struct tty *tty)
 {