Add a base-index session option to specify the first index checked when looking

for an index for a new window.

cmd-break-pane.c

@@ -48,6 +48,7 @@ cmd_break_pane_exec(struct cmd *self, struct cmd_ctx *ctx)
 	struct window_pane	*wp;
 	struct window		*w;
 	char			*cause;
+	int			 base_idx;
 
 	if ((wl = cmd_find_pane(ctx, data->target, &s, &wp)) == NULL)
 		return (-1);
@@ -71,7 +72,8 @@ cmd_break_pane_exec(struct cmd *self, struct cmd_ctx *ctx)
  	w->name = default_window_name(w);
 	layout_init(w);
 
- 	wl = session_attach(s, w, -1, &cause); /* can't fail */
+	base_idx = options_get_number(&s->options, "base-index");
+ 	wl = session_attach(s, w, -1 - base_idx, &cause); /* can't fail */
  	if (!(data->chflags & CMD_CHFLAG('d')))
  		session_select(s, wl->idx);
 

cmd-link-window.c

@@ -77,6 +77,8 @@ cmd_link_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 		}
 	}
 
+	if (idx == -1)
+		idx = -1 - options_get_number(&dst->options, "base-index");
 	wl_dst = session_attach(dst, wl_src->window, idx, &cause);
 	if (wl_dst == NULL) {
 		ctx->error(ctx, "create session failed: %s", cause);

cmd-move-window.c

@@ -79,6 +79,8 @@ cmd_move_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 		}
 	}
 
+	if (idx == -1)
+		idx = -1 - options_get_number(&dst->options, "base-index");
 	wl_dst = session_attach(dst, wl_src->window, idx, &cause);
 	if (wl_dst == NULL) {
 		ctx->error(ctx, "attach window failed: %s", cause);

cmd-new-session.c

@@ -118,7 +118,7 @@ cmd_new_session_exec(struct cmd *self, struct cmd_ctx *ctx)
 	struct termios			 tio;
 	const char			*update;
 	char				*overrides, *cmd, *cwd, *cause;
-	int				 detached;
+	int				 detached, idx;
 	u_int				 sx, sy;
 
 	if (data->newname != NULL && session_find(data->newname) != NULL) {
@@ -216,7 +216,9 @@ cmd_new_session_exec(struct cmd *self, struct cmd_ctx *ctx)
 	tio.c_ospeed = TTYDEF_SPEED;
 
 	/* Create the new session. */
-	s = session_create(data->newname, cmd, cwd, &env, &tio, sx, sy, &cause);
+	idx = -1 - options_get_number(&global_s_options, "base-index");
+	s = session_create(
+	    data->newname, cmd, cwd, &env, &tio, idx, sx, sy, &cause);
 	if (s == NULL) {
 		ctx->error(ctx, "create session failed: %s", cause);
 		xfree(cause);

cmd-new-window.c

@@ -154,6 +154,8 @@ cmd_new_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 	else
 		cwd = ctx->cmdclient->cwd;
 
+	if (idx == -1)
+		idx = -1 - options_get_number(&s->options, "base-index");
 	wl = session_new(s, data->name, cmd, cwd, idx, &cause);
 	if (wl == NULL) {
 		ctx->error(ctx, "create window failed: %s", cause);

cmd-set-option.c

@@ -50,6 +50,7 @@ const char *set_option_bell_action_list[] = {
 	"none", "any", "current", NULL
 };
 const struct set_option_entry set_option_table[] = {
+	{ "base-index", SET_OPTION_NUMBER, 0, INT_MAX, NULL },
 	{ "bell-action", SET_OPTION_CHOICE, 0, 0, set_option_bell_action_list },
 	{ "buffer-limit", SET_OPTION_NUMBER, 1, INT_MAX, NULL },
 	{ "default-command", SET_OPTION_STRING, 0, 0, NULL },

session.c

@@ -113,7 +113,8 @@ session_find(const char *name)
 /* Create a new session. */
 struct session *
 session_create(const char *name, const char *cmd, const char *cwd,
-    struct environ *env, struct termios *tio, u_int sx, u_int sy, char **cause)
+    struct environ *env, struct termios *tio, int idx, u_int sx, u_int sy,
+    char **cause)
 {
 	struct session	*s;
 	u_int		 i;
@@ -149,11 +150,11 @@ session_create(const char *name, const char *cmd, const char *cwd,
 		s->name = xstrdup(name);
 	else
 		xasprintf(&s->name, "%u", i);
-	if (session_new(s, NULL, cmd, cwd, -1, cause) == NULL) {
+	if (session_new(s, NULL, cmd, cwd, idx, cause) == NULL) {
 		session_destroy(s);
 		return (NULL);
 	}
-	session_select(s, 0);
+	session_select(s, RB_ROOT(&s->windows)->idx);
 
 	log_debug("session %s created", s->name);
 

tmux.1

@@ -1064,6 +1064,10 @@ options - it is not possible to unset a global option.
 .Pp
 Available session options are:
 .Bl -tag -width Ds
+.It Ic base-index Ar index
+Set the base index from which an unused index should be searched when a new
+window is created.
+The default is zero.
 .It Xo Ic bell-action
 .Op Ic any | none | current
 .Xc

tmux.c

@@ -342,6 +342,7 @@ main(int argc, char **argv)
 	}
 
 	options_init(&global_s_options, NULL);
+	options_set_number(&global_s_options, "base-index", 0);
 	options_set_number(&global_s_options, "bell-action", BELL_ANY);
 	options_set_number(&global_s_options, "buffer-limit", 9);
 	options_set_string(&global_s_options, "default-command", "%s", "");

tmux.h

@@ -1565,7 +1565,7 @@ RB_PROTOTYPE(windows, window, entry, window_cmp);
 RB_PROTOTYPE(winlinks, winlink, entry, winlink_cmp);
 struct winlink	*winlink_find_by_index(struct winlinks *, int);
 struct winlink 	*winlink_find_by_window(struct winlinks *, struct window *);
-int		 winlink_next_index(struct winlinks *);
+int		 winlink_next_index(struct winlinks *, int);
 u_int		 winlink_count(struct winlinks *);
 struct winlink	*winlink_add(struct winlinks *, struct window *, int);
 void		 winlink_remove(struct winlinks *, struct winlink *);
@@ -1670,7 +1670,8 @@ int	 session_alert_has(struct session *, struct winlink *, int);
 int	 session_alert_has_window(struct session *, struct window *, int);
 struct session	*session_find(const char *);
 struct session	*session_create(const char *, const char *, const char *,
-    		     struct environ *, struct termios *, u_int, u_int, char **);
+		     struct environ *, struct termios *, int, u_int, u_int,
+		     char **);
 void	 	 session_destroy(struct session *);
 int	 	 session_index(struct session *, u_int *);
 struct winlink	*session_new(struct session *,

window.c

@@ -122,16 +122,20 @@ winlink_find_by_index(struct winlinks *wwl, int idx)
 }
 
 int
-winlink_next_index(struct winlinks *wwl)
+winlink_next_index(struct winlinks *wwl, int idx)
 {
-	u_int	i;
+	int	i;
 
-	for (i = 0; i < INT_MAX; i++) {
+	i = idx;
+	do {
 		if (winlink_find_by_index(wwl, i) == NULL)
 			return (i);
-	}
-
-	fatalx("no free indexes");
+		if (i == INT_MAX)
+			i = 0;
+		else
+			i++;
+	} while (i != idx);
+	return (-1);
 }
 
 u_int
@@ -152,14 +156,12 @@ winlink_add(struct winlinks *wwl, struct window *w, int idx)
 {
 	struct winlink	*wl;
 
-	if (idx == -1)
-		idx = winlink_next_index(wwl);
-	else if (winlink_find_by_index(wwl, idx) != NULL)
+	if (idx < 0) {
+		if ((idx = winlink_next_index(wwl, -idx - 1)) == -1)
+			return (NULL);
+	} else if (winlink_find_by_index(wwl, idx) != NULL)
 		return (NULL);
 
-	if (idx < 0)
-		fatalx("bad index");
-
 	wl = xcalloc(1, sizeof *wl);
 	wl->idx = idx;
 	wl->window = w;