Implement ECH (erase character, CSI X). Reported by Christian Neukirchen.

input.c

@@ -135,6 +135,7 @@ enum input_csi_type {
 	INPUT_CSI_DECSTBM,
 	INPUT_CSI_DL,
 	INPUT_CSI_DSR,
+	INPUT_CSI_ECH,
 	INPUT_CSI_ED,
 	INPUT_CSI_EL,
 	INPUT_CSI_HPA,
@@ -167,6 +168,7 @@ const struct input_table_entry input_csi_table[] = {
 	{ 'L', "",  INPUT_CSI_IL },
 	{ 'M', "",  INPUT_CSI_DL },
 	{ 'P', "",  INPUT_CSI_DCH },
+	{ 'X', "",  INPUT_CSI_ECH },
 	{ 'Z', "",  INPUT_CSI_CBT },
 	{ 'c', "",  INPUT_CSI_DA },
 	{ 'c', ">", INPUT_CSI_DA_TWO },
@@ -1143,6 +1145,9 @@ input_csi_dispatch(struct input_ctx *ictx)
 			break;
 		}
 		break;
+	case INPUT_CSI_ECH:
+		screen_write_clearcharacter(sctx, input_get(ictx, 0, 1, 1));
+		break;
 	case INPUT_CSI_DCH:
 		screen_write_deletecharacter(sctx, input_get(ictx, 0, 1, 1));
 		break;

screen-write.c

@@ -649,6 +649,30 @@ screen_write_deletecharacter(struct screen_write_ctx *ctx, u_int nx)
 	tty_write(tty_cmd_deletecharacter, &ttyctx);
 }
 
+/* Clear nx characters. */
+void
+screen_write_clearcharacter(struct screen_write_ctx *ctx, u_int nx)
+{
+	struct screen	*s = ctx->s;
+	struct tty_ctx	 ttyctx;
+
+	if (nx == 0)
+		nx = 1;
+
+	if (nx > screen_size_x(s) - s->cx)
+		nx = screen_size_x(s) - s->cx;
+	if (nx == 0)
+		return;
+
+	screen_write_initctx(ctx, &ttyctx, 0);
+
+	if (s->cx <= screen_size_x(s) - 1)
+		grid_view_clear(s->grid, s->cx, s->cy, nx, 1);
+
+	ttyctx.num = nx;
+	tty_write(tty_cmd_clearcharacter, &ttyctx);
+}
+
 /* Insert ny lines. */
 void
 screen_write_insertline(struct screen_write_ctx *ctx, u_int ny)

tmux.h

@@ -274,6 +274,7 @@ enum tty_code_code {
 	TTYC_DL,	/* parm_delete_line, DL */
 	TTYC_DL1,	/* delete_line, dl */
 	TTYC_E3,
+	TTYC_ECH,	/* erase_chars, ec */
 	TTYC_EL,	/* clr_eol, ce */
 	TTYC_EL1,	/* clr_bol, cb */
 	TTYC_ENACS,	/* ena_acs, eA */
@@ -1660,6 +1661,7 @@ void	tty_cmd_clearscreen(struct tty *, const struct tty_ctx *);
 void	tty_cmd_clearstartofline(struct tty *, const struct tty_ctx *);
 void	tty_cmd_clearstartofscreen(struct tty *, const struct tty_ctx *);
 void	tty_cmd_deletecharacter(struct tty *, const struct tty_ctx *);
+void	tty_cmd_clearcharacter(struct tty *, const struct tty_ctx *);
 void	tty_cmd_deleteline(struct tty *, const struct tty_ctx *);
 void	tty_cmd_erasecharacter(struct tty *, const struct tty_ctx *);
 void	tty_cmd_insertcharacter(struct tty *, const struct tty_ctx *);
@@ -2049,6 +2051,7 @@ void	 screen_write_cursorleft(struct screen_write_ctx *, u_int);
 void	 screen_write_alignmenttest(struct screen_write_ctx *);
 void	 screen_write_insertcharacter(struct screen_write_ctx *, u_int);
 void	 screen_write_deletecharacter(struct screen_write_ctx *, u_int);
+void	 screen_write_clearcharacter(struct screen_write_ctx *, u_int);
 void	 screen_write_insertline(struct screen_write_ctx *, u_int);
 void	 screen_write_deleteline(struct screen_write_ctx *, u_int);
 void	 screen_write_clearline(struct screen_write_ctx *);

tty-term.c

@@ -62,6 +62,7 @@ const struct tty_term_code_entry tty_term_codes[NTTYCODE] = {
 	{ TTYC_DL, TTYCODE_STRING, "dl" },
 	{ TTYC_DL1, TTYCODE_STRING, "dl1" },
 	{ TTYC_E3, TTYCODE_STRING, "E3" },
+	{ TTYC_ECH, TTYCODE_STRING, "ech" },
 	{ TTYC_EL, TTYCODE_STRING, "el" },
 	{ TTYC_EL1, TTYCODE_STRING, "el1" },
 	{ TTYC_ENACS, TTYCODE_STRING, "enacs" },

tty.c

@@ -718,6 +718,23 @@ tty_cmd_deletecharacter(struct tty *tty, const struct tty_ctx *ctx)
 		tty_emulate_repeat(tty, TTYC_DCH, TTYC_DCH1, ctx->num);
 }
 
+void
+tty_cmd_clearcharacter(struct tty *tty, const struct tty_ctx *ctx)
+{
+	u_int	i;
+
+	tty_reset(tty);
+
+	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
+
+	if (tty_term_has(tty->term, TTYC_ECH))
+		tty_putcode1(tty, TTYC_ECH, ctx->num);
+	else {
+		for (i = 0; i < ctx->num; i++)
+			tty_putc(tty, ' ');
+	}
+}
+
 void
 tty_cmd_insertline(struct tty *tty, const struct tty_ctx *ctx)
 {