Fix \watch's interaction with libedit on ^C.

When you hit ^C, the terminal driver in Unix-like systems echoes "^C" as
well as sending an interrupt signal (depending on stty settings).  At
least libedit (but maybe also libreadline) is then confused about the
current cursor location, and corrupts the display if you try to scroll
back.  Fix, by moving to a new line before the next prompt is displayed.

Back-patch to all supported released.

Author: Pavel Stehule <pavel.stehule@gmail.com>
Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/3278793.1626198638%40sss.pgh.pa.us

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index 7218e7798bbfa6a29940d0af15ed00aab346a459..8889f83371403ae683e80abfaa133fe40d313ede 100644 (file)
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -4675,6 +4675,14 @@ do_watch(PQExpBuffer query_buf, double sleep)
        sigint_interrupt_enabled = false;
    }
 
+   /*
+    * If the terminal driver echoed "^C", libedit/libreadline might be
+    * confused about the cursor position.  Therefore, inject a newline
+    * before the next prompt is displayed.
+    */
+   fprintf(stdout, "\n");
+   fflush(stdout);
+
    pg_free(title);
    return (res >= 0);
 }