Add a capability for OSC 7 and use it similarly to how the title is set

(and controlled by the same set-titles option). GitHub issue 3127.

server-client.c

@@ -43,6 +43,7 @@ static void	server_client_check_exit(struct client *);
 static void	server_client_check_redraw(struct client *);
 static void	server_client_check_modes(struct client *);
 static void	server_client_set_title(struct client *);
+static void	server_client_set_path(struct client *);
 static void	server_client_reset_state(struct client *);
 static int	server_client_assume_paste(struct session *);
 static void	server_client_update_latest(struct client *);
@@ -2603,8 +2604,10 @@ server_client_check_redraw(struct client *c)
 	}
 
 	if (c->flags & CLIENT_ALLREDRAWFLAGS) {
-		if (options_get_number(s->options, "set-titles"))
+		if (options_get_number(s->options, "set-titles")) {
 			server_client_set_title(c);
+			server_client_set_path(c);
+		}
 		screen_redraw_screen(c);
 	}
 
@@ -2650,6 +2653,26 @@ server_client_set_title(struct client *c)
 	format_free(ft);
 }
 
+/* Set client path. */
+static void
+server_client_set_path(struct client *c)
+{
+	struct session	*s = c->session;
+	const char	*path;
+
+	if (s->curw == NULL)
+		return;
+	if (s->curw->window->active->base.path == NULL)
+		path = "";
+	else
+		path = s->curw->window->active->base.path;
+	if (c->path == NULL || strcmp(path, c->path) != 0) {
+		free(c->path);
+		c->path = xstrdup(path);
+		tty_set_path(&c->tty, c->path);
+	}
+}
+
 /* Dispatch message from client. */
 static void
 server_client_dispatch(struct imsg *imsg, void *arg)

tmux.1

@@ -3624,6 +3624,8 @@ Supports DECSLRM margins.
 Supports
 .Xr xterm 1
 mouse sequences.
+.It osc7
+Supports the OSC 7 working directory extension.
 .It overline
 Supports the overline SGR attribute.
 .It rectfill
@@ -6391,6 +6393,11 @@ $ printf '\e033[4 q'
 If
 .Em Se
 is not set, \&Ss with argument 0 will be used to reset the cursor style instead.
+.It Em \&Swd
+Set the opening sequence for the working directory notification.
+The sequence is terminated using the standard
+.Em fsl
+capability.
 .It Em \&Sync
 Start (parameter is 1) or end (parameter is 2) a synchronized update.
 .It Em \&Tc

tmux.h

@@ -539,6 +539,7 @@ enum tty_code_code {
 	TTYC_SMULX,
 	TTYC_SMXX,
 	TTYC_SS,
+	TTYC_SWD,
 	TTYC_SYNC,
 	TTYC_TC,
 	TTYC_TSL,
@@ -1708,6 +1709,7 @@ struct client {
 	struct format_job_tree	*jobs;
 
 	char			*title;
+	char			*path;
 	const char		*cwd;
 
 	char			*term_name;
@@ -2258,6 +2260,7 @@ void	tty_start_tty(struct tty *);
 void	tty_send_requests(struct tty *);
 void	tty_stop_tty(struct tty *);
 void	tty_set_title(struct tty *, const char *);
+void	tty_set_path(struct tty *, const char *);
 void	tty_update_mode(struct tty *, int, struct screen *);
 void	tty_draw_line(struct tty *, struct screen *, u_int, u_int, u_int,
 	    u_int, u_int, const struct grid_cell *, struct colour_palette *);

tty-features.c

@@ -53,6 +53,18 @@ static const struct tty_feature tty_feature_title = {
 	0
 };
 
+/* Terminal has OSC 7 working directory. */
+static const char *tty_feature_osc7_capabilities[] = {
+	"Swd=\\E]7;",
+	"fsl=\\a",
+	NULL
+};
+static const struct tty_feature tty_feature_osc7 = {
+	"osc7",
+	tty_feature_osc7_capabilities,
+	0
+};
+
 /* Terminal has mouse support. */
 static const char *tty_feature_mouse_capabilities[] = {
 	"kmous=\\E[M",
@@ -249,6 +261,7 @@ static const struct tty_feature *tty_features[] = {
 	&tty_feature_focus,
 	&tty_feature_margins,
 	&tty_feature_mouse,
+	&tty_feature_osc7,
 	&tty_feature_overline,
 	&tty_feature_rectfill,
 	&tty_feature_rgb,

tty-term.c

@@ -274,6 +274,7 @@ static const struct tty_term_code_entry tty_term_codes[] = {
 	[TTYC_SMUL] = { TTYCODE_STRING, "smul" },
 	[TTYC_SMXX] =  { TTYCODE_STRING, "smxx" },
 	[TTYC_SS] = { TTYCODE_STRING, "Ss" },
+	[TTYC_SWD] = { TTYCODE_STRING, "Swd" },
 	[TTYC_SYNC] = { TTYCODE_STRING, "Sync" },
 	[TTYC_TC] = { TTYCODE_FLAG, "Tc" },
 	[TTYC_TSL] = { TTYCODE_STRING, "tsl" },

tty.c

@@ -655,6 +655,18 @@ tty_set_title(struct tty *tty, const char *title)
 	tty_putcode(tty, TTYC_FSL);
 }
 
+void
+tty_set_path(struct tty *tty, const char *title)
+{
+	if (!tty_term_has(tty->term, TTYC_SWD) ||
+	    !tty_term_has(tty->term, TTYC_FSL))
+		return;
+
+	tty_putcode(tty, TTYC_SWD);
+	tty_puts(tty, title);
+	tty_putcode(tty, TTYC_FSL);
+}
+
 static void
 tty_force_cursor_colour(struct tty *tty, int c)
 {