Use the tsl and fsl terminfo(5) capabilities to update terminal title

and automatically fill them in on terminals with the XT capability
(which means their title setting is xterm-compatible). From hsim at
gmx.li.

options-table.c

@@ -355,7 +355,7 @@ const struct options_table_entry session_options_table[] = {
 
 	{ .name = "terminal-overrides",
 	  .type = OPTIONS_TABLE_STRING,
-	  .default_str = "*88col*:colors=88,*256col*:colors=256"
+	  .default_str = "*88col*:colors=88,*256col*:colors=256,xterm*:XT"
 	},
 
 	{ .name = "update-environment",

tmux.1

@@ -2145,7 +2145,7 @@ The default value forcibly corrects the
 .Ql colors
 entry for terminals which support 88 or 256 colours:
 .Bd -literal -offset indent
-"*88col*:colors=88,*256col*:colors=256"
+"*88col*:colors=88,*256col*:colors=256,xterm*:XT"
 .Ed
 .It Ic update-environment Ar variables
 Set a space-separated string containing a list of environment variables to be

tmux.h

@@ -205,6 +205,7 @@ enum tty_code_code {
 	TTYC_EL,	/* clr_eol, ce */
 	TTYC_EL1,	/* clr_bol, cb */
 	TTYC_ENACS,	/* ena_acs, eA */
+	TTYC_FSL,	/* from_status_line, fsl */
 	TTYC_HOME,	/* cursor_home, ho */
 	TTYC_HPA,	/* column_address, ch */
 	TTYC_ICH,	/* parm_ich, IC */
@@ -317,17 +318,19 @@ enum tty_code_code {
 	TTYC_SETAB,	/* set_a_background, AB */
 	TTYC_SETAF,	/* set_a_foreground, AF */
 	TTYC_SGR0,	/* exit_attribute_mode, me */
+	TTYC_SITM,	/* enter_italics_mode, it */
 	TTYC_SMACS,	/* enter_alt_charset_mode, as */
 	TTYC_SMCUP,	/* enter_ca_mode, ti */
 	TTYC_SMIR,	/* enter_insert_mode, im */
 	TTYC_SMKX,	/* keypad_xmit, ks */
 	TTYC_SMSO,	/* enter_standout_mode, so */
 	TTYC_SMUL,	/* enter_underline_mode, us */
-	TTYC_SITM,	/* enter_italics_mode, it */
+	TTYC_TSL,	/* to_status_line, tsl */
 	TTYC_VPA,	/* row_address, cv */
 	TTYC_XENL,	/* eat_newline_glitch, xn */
+	TTYC_XT,	/* xterm(1)-compatible title, XT */
 };
-#define NTTYCODE (TTYC_XENL + 1)
+#define NTTYCODE (TTYC_XT + 1)
 
 /* Termcap types. */
 enum tty_code_type {

tty-term.c

@@ -60,6 +60,7 @@ const struct tty_term_code_entry tty_term_codes[NTTYCODE] = {
 	{ TTYC_EL, TTYCODE_STRING, "el" },
 	{ TTYC_EL1, TTYCODE_STRING, "el1" },
 	{ TTYC_ENACS, TTYCODE_STRING, "enacs" },
+	{ TTYC_FSL, TTYCODE_STRING, "fsl" },
 	{ TTYC_HOME, TTYCODE_STRING, "home" },
 	{ TTYC_HPA, TTYCODE_STRING, "hpa" },
 	{ TTYC_ICH, TTYCODE_STRING, "ich" },
@@ -172,15 +173,17 @@ const struct tty_term_code_entry tty_term_codes[NTTYCODE] = {
 	{ TTYC_SETAB, TTYCODE_STRING, "setab" },
 	{ TTYC_SETAF, TTYCODE_STRING, "setaf" },
 	{ TTYC_SGR0, TTYCODE_STRING, "sgr0" },
+	{ TTYC_SITM, TTYCODE_STRING, "sitm" },
 	{ TTYC_SMACS, TTYCODE_STRING, "smacs" },
 	{ TTYC_SMCUP, TTYCODE_STRING, "smcup" },
 	{ TTYC_SMIR, TTYCODE_STRING, "smir" },
 	{ TTYC_SMKX, TTYCODE_STRING, "smkx" },
 	{ TTYC_SMSO, TTYCODE_STRING, "smso" },
 	{ TTYC_SMUL, TTYCODE_STRING, "smul" },
-	{ TTYC_SITM, TTYCODE_STRING, "sitm" },
+	{ TTYC_TSL, TTYCODE_STRING, "tsl" },
 	{ TTYC_VPA, TTYCODE_STRING, "vpa" },
 	{ TTYC_XENL, TTYCODE_FLAG, "xenl" },
+	{ TTYC_XT, TTYCODE_FLAG, "XT" },
 };
 
 char *
@@ -252,7 +255,7 @@ tty_term_override(struct tty_term *term, const char *overrides)
 				entstr[strlen(entstr) - 1] = '\0';
 				removeflag = 1;
 			} else
-				continue;
+				val = xstrdup("");
 
 			for (i = 0; i < NTTYCODE; i++) {
 				ent = &tty_term_codes[i];
@@ -423,6 +426,18 @@ tty_term_find(char *name, int fd, const char *overrides, char **cause)
 	for (; acs[0] != '\0' && acs[1] != '\0'; acs += 2)
 		term->acs[(u_char) acs[0]][0] = acs[1];
 
+	/* On terminals with xterm titles (XT), fill in tsl and fsl. */
+	if (tty_term_flag(term, TTYC_XT) &&
+	    !tty_term_has(term, TTYC_TSL) &&
+	    !tty_term_has(term, TTYC_FSL)) {
+		code = &term->codes[TTYC_TSL];
+		code->value.string = xstrdup("\033]0;");
+		code->type = TTYCODE_STRING;
+		code = &term->codes[TTYC_FSL];
+		code->value.string = xstrdup("\007");
+		code->type = TTYCODE_STRING;
+	}
+
 	return (term);
 
 error:

tty.c

@@ -369,14 +369,13 @@ tty_pututf8(struct tty *tty, const struct grid_utf8 *gu)
 void
 tty_set_title(struct tty *tty, const char *title)
 {
-	if (strstr(tty->termname, "xterm") == NULL &&
+	if (!tty_term_has(tty->term, TTYC_TSL) ||
-	    strstr(tty->termname, "rxvt") == NULL &&
+	    !tty_term_has(tty->term, TTYC_FSL))
-	    strcmp(tty->termname, "screen") != 0)
 		return;
 
-	tty_puts(tty, "\033]0;");
+	tty_putcode(tty, TTYC_TSL);
 	tty_puts(tty, title);
-	tty_putc(tty, '\007');
+	tty_putcode(tty, TTYC_FSL);
 }
 
 void