From 10ef5a8596d692aef016ada0718e8783bb05aeeb Mon Sep 17 00:00:00 2001
From: Andrew Wood <andrew.wood@ivarch.com>
Date: Sun, 28 Sep 2025 16:36:06 +0100
Subject: [PATCH] If watching more than one distinct PID with --watchfd,
 display the PID as well as the FD number (#12).

---
 src/include/pv-internal.h |  1 +
 src/pv/loop.c             |  1 -
 src/pv/state.c            |  6 ++++++
 src/pv/watchpid.c         | 33 ++++++++++++++++++++++++++-------
 4 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/src/include/pv-internal.h b/src/include/pv-internal.h
index 9b95780..9157e70 100644
--- a/src/include/pv-internal.h
+++ b/src/include/pv-internal.h
@@ -167,6 +167,7 @@ struct pvstate_s {
 		/*@only@*/ /*@null@*/ pid_t *pid; /* array of processes to watch fds of */
 		/*@only@*/ /*@null@*/ int *fd;	/* array of fds to watch in each one (0=all) */
 		unsigned int count;	/* number of items in these arrays */
+		bool multiple_pids;	/* true if more than one distinct PID */
 	} watchfd;
 
 	/*******************
diff --git a/src/pv/loop.c b/src/pv/loop.c
index 91aefb9..fadd256 100644
--- a/src/pv/loop.c
+++ b/src/pv/loop.c
@@ -593,7 +593,6 @@ int pv_main_loop(pvstate_t state)
  *
  * Returns nonzero on error.
  *
- * TODO: if more than one PID is being watched, display the PID as well.
  * TODO: re-add "%N" after receiving a remote update, e.g. "-R pid -u block".
  */
 int pv_watchfd_loop(pvstate_t state)
diff --git a/src/pv/state.c b/src/pv/state.c
index 175b10b..2eda4d1 100644
--- a/src/pv/state.c
+++ b/src/pv/state.c
@@ -721,6 +721,7 @@ void pv_state_watchfds(pvstate_t state, unsigned int watchfd_count, const pid_t
 		state->watchfd.fd = NULL;
 	}
 	state->watchfd.count = 0;
+	state->watchfd.multiple_pids = false;
 
 	/* Allocate empty new arrays of the right size. */
 	new_pid_array = calloc((size_t) (watchfd_count + 1), sizeof(pid_t));
@@ -744,6 +745,11 @@ void pv_state_watchfds(pvstate_t state, unsigned int watchfd_count, const pid_t
 	for (item_idx = 0; item_idx < watchfd_count; item_idx++) {
 		state->watchfd.pid[item_idx] = pids[item_idx];
 		state->watchfd.fd[item_idx] = fds[item_idx];
+		if ((item_idx > 0) && (pids[item_idx] != pids[item_idx - 1]))
+			state->watchfd.multiple_pids = true;
 	}
 	state->watchfd.count = watchfd_count;
+
+	debug("%s=%d, %s=%s", "watchfd.count", state->watchfd.count, "multiple_pids",
+	      state->watchfd.multiple_pids ? "true" : "false");
 }
diff --git a/src/pv/watchpid.c b/src/pv/watchpid.c
index a7994d4..77fed08 100644
--- a/src/pv/watchpid.c
+++ b/src/pv/watchpid.c
@@ -617,6 +617,9 @@ int pv_watchpid_scanfds(pvstate_t state, pid_t watch_pid, int watch_fd, int *arr
  * Set the display name for the given watched file descriptor, truncating at
  * the relevant places according to the current screen width.
  *
+ * If more than one distinct PID is being watched, include the PID in the
+ * name as well as the file descriptor number.
+ *
  * If the file descriptor is pointing to a file under the current working
  * directory, show its relative path, not the full path.
  */
@@ -639,20 +642,36 @@ void pv_watchpid_setname(pvstate_t state, pvwatchfd_t info)
 	}
 
 	max_display_length = (int) (state->control.width / 2) - 6;
+	if (state->watchfd.multiple_pids)
+		max_display_length -= 9;
 	if (max_display_length >= (int) path_length) {
-		(void) pv_snprintf(info->display_name,
-				   PV_SIZEOF_DISPLAY_NAME, "%4d:%.498s", info->watch_fd, file_fdpath);
+		if (state->watchfd.multiple_pids) {
+			(void) pv_snprintf(info->display_name,
+					   PV_SIZEOF_DISPLAY_NAME, "%8d:%4d:%.498s", (int) (info->watch_pid),
+					   info->watch_fd, file_fdpath);
+		} else {
+			(void) pv_snprintf(info->display_name,
+					   PV_SIZEOF_DISPLAY_NAME, "%4d:%.498s", info->watch_fd, file_fdpath);
+		}
 	} else {
 		int prefix_length, suffix_length;
 
 		prefix_length = max_display_length / 4;
 		suffix_length = max_display_length - prefix_length - 3;
 
-		(void) pv_snprintf(info->display_name,
-				   PV_SIZEOF_DISPLAY_NAME,
-				   "%4d:%.*s...%.*s",
-				   info->watch_fd, prefix_length,
-				   file_fdpath, suffix_length, file_fdpath + path_length - suffix_length);
+		if (state->watchfd.multiple_pids) {
+			(void) pv_snprintf(info->display_name,
+					   PV_SIZEOF_DISPLAY_NAME,
+					   "%8d:%4d:%.*s...%.*s",
+					   (int) (info->watch_pid), info->watch_fd, prefix_length,
+					   file_fdpath, suffix_length, file_fdpath + path_length - suffix_length);
+		} else {
+			(void) pv_snprintf(info->display_name,
+					   PV_SIZEOF_DISPLAY_NAME,
+					   "%4d:%.*s...%.*s",
+					   info->watch_fd, prefix_length,
+					   file_fdpath, suffix_length, file_fdpath + path_length - suffix_length);
+		}
 	}
 
 	debug("%s: %d: [%s]", "set name for fd", info->watch_fd, info->display_name);