terminal-util: add new helper terminal_reset_defensive() that combines reset-by-ioctl and reset-by-sequence reasonably

src/basic/terminal-util.c

@@ -1575,6 +1575,27 @@ int terminal_reset_ansi_seq(int fd) {
         return k < 0 ? k : r;
 }
 
+int terminal_reset_defensive(int fd, bool switch_to_text) {
+        int r = 0;
+
+        assert(fd >= 0);
+
+        /* Resets the terminal comprehensively, but defensively. i.e. both resets the tty via ioctl()s and
+         * via ANSI sequences, but avoids the latter in case we are talking to a pty. That's a safety measure
+         * because ptys might be connected to shell pipelines where we cannot expect such ansi sequences to
+         * work. Given that ptys are generally short-lived (and not recycled) this restriction shouldn't hurt
+         * much.
+         *
+         * The specified fd should be open for *writing*! */
+
+        RET_GATHER(r, reset_terminal_fd(fd, switch_to_text));
+
+        if (terminal_is_pty_fd(fd) == 0)
+                RET_GATHER(r, terminal_reset_ansi_seq(fd));
+
+        return r;
+}
+
 void termios_disable_echo(struct termios *termios) {
         assert(termios);
 

src/basic/terminal-util.h

@@ -98,6 +98,7 @@ bool isatty_safe(int fd);
 int reset_terminal_fd(int fd, bool switch_to_text);
 int reset_terminal(const char *name);
 int terminal_reset_ansi_seq(int fd);
+int terminal_reset_defensive(int fd, bool switch_to_text);
 
 int terminal_set_cursor_position(int fd, unsigned row, unsigned column);