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Added a possible workaround, and extra debugging, for the missing display output issue in #100, but turned off at the moment.

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This commit is contained in:
Andrew Wood
2024-10-09 22:07:56 +01:00
parent e433ad319e
commit ec498ec476
1 changed files with 75 additions and 5 deletions
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src/pv/display.c
+75 -5
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@@ -23,6 +23,9 @@
#include <termios.h>
#endif
/* Use tcsetpgrp() workaround - see issue #100 and comments below. */
/* #define USE_TCSETPGRP 1 */
/*
* We need sys/ioctl.h for ioctl() regardless of whether TIOCGWINSZ is
* defined in termios.h, so we no longer use AC_HEADER_TIOCGWINSZ in
@@ -66,7 +69,7 @@ bool pv_in_foreground(void)
pid_t tty_process_group;
if (0 == isatty(STDERR_FILENO)) {
debug("%s: true: %s", "pv_in_foreground", "not a tty");
debug("true: %s", "not a tty");
return true;
}
@@ -76,17 +79,84 @@ bool pv_in_foreground(void)
/*@+type@ */
if (tty_process_group == -1 && errno == ENOTTY) {
debug("%s: true: %s", "pv_in_foreground", "tty_process_group is -1, errno is ENOTTY");
debug("true: %s", "tty_process_group is -1, errno is ENOTTY");
return true;
}
if (our_process_group == tty_process_group) {
debug("%s: true: %s", "pv_in_foreground", "our_process_group == tty_process_group");
debug("true: %s (%d)", "our_process_group == tty_process_group", our_process_group);
return true;
}
#if USE_TCSETPGRP
/*
* If the terminal process group ID isn't our own process group ID,
* then first check that the terminal process group ID actually
* exists.
*/
debug("%s: false: our_process_group=%d, tty_process_group=%d",
"pv_in_foreground", our_process_group, tty_process_group);
if (0 == kill(-tty_process_group, 0)) {
/*
* If it does exist, then we're not in the foreground, so
* return false.
*/
debug("false: our_process_group=%d, tty_process_group=(%d and confirmed to exist)",
our_process_group, tty_process_group);
} else if (errno == ESRCH) {
/*
* If it doesn't exist (kill(0) gave ESRCH), then try
* setting the terminal process group ID back to our process
* group ID, to forcibly put ourselves into the foreground
* (see issue #100), and try reading it back again. If we
* successfully set it to our process group ID then we're in
* the foreground, so return true; otherwise we can't be
* sure we're in the foreground, so return false.
*
* This is because the manual says the function tcgetpgrp()
* will return the foreground process group ID of that
* terminal if there is one, and some value larger than 1
* that is not presently a process group ID otherwise.
*
* The assumption we're making is that tcgetpgrp() can
* return a non-pgid value if there's no pgid for this
* terminal right now, implying that maybe we can just set
* it to our own.
*/
debug("-: our_process_group=%d, tty_process_group=(%d which returned ESRCH)",
our_process_group, tty_process_group);
/*@-type@ *//* __pid_t vs pid_t, not significant */
if (0 == tcsetpgrp(STDERR_FILENO, our_process_group)) {
tty_process_group = tcgetpgrp(STDERR_FILENO);
/*@+type@ */
if (our_process_group == tty_process_group) {
debug
("true: our_process_group == tty_process_group (after tcsetpgrp to change it to %d)",
our_process_group);
return true;
}
debug("false: our_process_group=%d, tty_process_group=(%d even after tcsetpgrp)",
our_process_group, tty_process_group);
} else {
debug("false: our_process_group=%d, tty_process_group=(%d and tcsetpgrp returned \"%s\")",
our_process_group, tty_process_group, strerror(errno));
}
} else {
/*
* We can't determine whether the terminal process group ID
* exists, all we know is it doesn't match our own, so
* assume we're in the background, and return false.
*/
debug("false: our_process_group=%d, tty_process_group=(%d, kill returned \"%s\")",
our_process_group, tty_process_group, strerror(errno));
}
#else
/*
* Simply assume we're in the background, if the terminal process
* group ID doesn't match our own.
*/
debug("false: our_process_group=%d, tty_process_group=%d, errno is %d",
our_process_group, tty_process_group, (int) errno);
#endif
return false;
}