From 579115bd8030bcb948465f30a110b4809584e290 Mon Sep 17 00:00:00 2001
From: nicm <nicm@openbsd.org>
Date: Mon, 1 Feb 2021 08:01:14 +0000
Subject: [PATCH] Add a no-detached choice to detach-on-destroy which detaches
 only if there are no other detached sessions to switch to, from Sencer Selcuk
 in GitHub issue 2553.

---
 usr.bin/tmux/options-table.c |  8 ++++++--
 usr.bin/tmux/server-fn.c     | 27 ++++++++++++++++++++++-----
 usr.bin/tmux/tmux.1          | 10 +++++++---
 3 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/usr.bin/tmux/options-table.c b/usr.bin/tmux/options-table.c
index 18ba826c91d..eac3cb5d5c2 100644
--- a/usr.bin/tmux/options-table.c
+++ b/usr.bin/tmux/options-table.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: options-table.c,v 1.138 2021/01/20 07:16:54 nicm Exp $ */
+/* $OpenBSD: options-table.c,v 1.139 2021/02/01 08:01:14 nicm Exp $ */
 
 /*
  * Copyright (c) 2011 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -72,6 +72,9 @@ static const char *options_table_window_size_list[] = {
 static const char *options_table_remain_on_exit_list[] = {
 	"off", "on", "failed", NULL
 };
+static const char *options_table_detach_on_destroy_list[] = {
+	"off", "on", "no-detached", NULL
+};
 
 /* Status line format. */
 #define OPTIONS_TABLE_STATUS_FORMAT1 \
@@ -405,8 +408,9 @@ const struct options_table_entry options_table[] = {
 	},
 
 	{ .name = "detach-on-destroy",
-	  .type = OPTIONS_TABLE_FLAG,
+	  .type = OPTIONS_TABLE_CHOICE,
 	  .scope = OPTIONS_TABLE_SESSION,
+	  .choices = options_table_detach_on_destroy_list,
 	  .default_num = 1,
 	  .text = "Whether to detach when a session is destroyed, or switch "
 		  "the client to another session if any exist."
diff --git a/usr.bin/tmux/server-fn.c b/usr.bin/tmux/server-fn.c
index 6ad70961b0d..4dce8243816 100644
--- a/usr.bin/tmux/server-fn.c
+++ b/usr.bin/tmux/server-fn.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: server-fn.c,v 1.129 2021/01/04 08:43:16 nicm Exp $ */
+/* $OpenBSD: server-fn.c,v 1.130 2021/02/01 08:01:14 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -401,9 +401,8 @@ server_destroy_session_group(struct session *s)
 static struct session *
 server_next_session(struct session *s)
 {
-	struct session *s_loop, *s_out;
+	struct session *s_loop, *s_out = NULL;
 
-	s_out = NULL;
 	RB_FOREACH(s_loop, sessions, &sessions) {
 		if (s_loop == s)
 			continue;
@@ -414,17 +413,35 @@ server_next_session(struct session *s)
 	return (s_out);
 }
 
+static struct session *
+server_next_detached_session(struct session *s)
+{
+	struct session *s_loop, *s_out = NULL;
+
+	RB_FOREACH(s_loop, sessions, &sessions) {
+		if (s_loop == s || s_loop->attached)
+			continue;
+		if (s_out == NULL ||
+		    timercmp(&s_loop->activity_time, &s_out->activity_time, <))
+			s_out = s_loop;
+	}
+	return (s_out);
+}
+
 void
 server_destroy_session(struct session *s)
 {
 	struct client	*c;
 	struct session	*s_new;
+	int		 detach_on_destroy;
 
-	if (!options_get_number(s->options, "detach-on-destroy"))
+	detach_on_destroy = options_get_number(s->options, "detach-on-destroy");
+	if (detach_on_destroy == 0)
 		s_new = server_next_session(s);
+	else if (detach_on_destroy == 2)
+		s_new = server_next_detached_session(s);
 	else
 		s_new = NULL;
-
 	TAILQ_FOREACH(c, &clients, entry) {
 		if (c->session != s)
 			continue;
diff --git a/usr.bin/tmux/tmux.1 b/usr.bin/tmux/tmux.1
index be88ebd4da8..6d6f806e4be 100644
--- a/usr.bin/tmux/tmux.1
+++ b/usr.bin/tmux/tmux.1
@@ -1,4 +1,4 @@
-.\" $OpenBSD: tmux.1,v 1.814 2021/01/29 09:48:43 nicm Exp $
+.\" $OpenBSD: tmux.1,v 1.815 2021/02/01 08:01:14 nicm Exp $
 .\"
 .\" Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
 .\"
@@ -14,7 +14,7 @@
 .\" IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 .\" OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: January 29 2021 $
+.Dd $Mdocdate: February 1 2021 $
 .Dt TMUX 1
 .Os
 .Sh NAME
@@ -3575,12 +3575,16 @@ The default is 80x24.
 If enabled and the session is no longer attached to any clients, it is
 destroyed.
 .It Xo Ic detach-on-destroy
-.Op Ic on | off
+.Op Ic off | on | no-detached
 .Xc
 If on (the default), the client is detached when the session it is attached to
 is destroyed.
 If off, the client is switched to the most recently active of the remaining
 sessions.
+If
+.Ic no-detached ,
+the client is detached only if there are no detached sessions; if detached
+sessions exist, the client is switched to the most recently active.
 .It Ic display-panes-active-colour Ar colour
 Set the colour used by the
 .Ic display-panes
-- 
2.20.1