From 0aac6d6aacfae9b785db60cf72895c3ceb5a5250 Mon Sep 17 00:00:00 2001
From: Andrew Wood <andrew.wood@ivarch.com>
Date: Fri, 17 Oct 2025 19:09:46 +0100
Subject: [PATCH] Add comments and "pid_last_seen", "fd_last_seen" structure
 members for proposed new logic that will hold fd info on-screen a short time
 after closure, to retain the progress display when a watched process exits
 (#81).

---
 src/include/pv-internal.h |  8 ++++++++
 src/pv/loop.c             | 21 +++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/src/include/pv-internal.h b/src/include/pv-internal.h
index 34384b6..07f4518 100644
--- a/src/include/pv-internal.h
+++ b/src/include/pv-internal.h
@@ -520,10 +520,18 @@ struct pvwatchfd_s {
 	off_t size;			 /* size of whole file, 0 if unknown */
 	off_t position;			 /* position last seen at */
 	struct timespec start_time;	 /* time we started watching the fd */
+	struct timespec fd_last_seen;	 /* time the fd was last seen open */
 	pid_t watch_pid;		 /* PID to watch */
 	int watch_fd;			 /* fd to watch */
 	bool displayable;		 /* false if not displayable */
 	bool unused;			 /* true if free for re-use */
+	/*
+	 * After the "watch_fd" is found to be closed, "fd_last_seen" stops
+	 * being updated; when "fd_last_seen" is old enough, "unused"
+	 * becomes true so the slot can be re-used.  This allows fd
+	 * information to be held on-screen for a short while after the fd
+	 * is closed (#81).
+	 */
 };
 typedef struct pvwatchfd_s *pvwatchfd_t;
 
diff --git a/src/pv/loop.c b/src/pv/loop.c
index cd4caf5..1b6c191 100644
--- a/src/pv/loop.c
+++ b/src/pv/loop.c
@@ -712,6 +712,7 @@ int pv_watchfd_loop(pvstate_t state)
 		int fd;			 /* watched fd, or -1 for all */
 		pvwatchfd_t info_array;	 /* watch information for each fd */
 		int array_length;	 /* length of watch info array */
+		struct timespec pid_last_seen;	/* when this PID was last seen */
 		bool finished;		 /* "PID:FD": fd closed; or PID gone */
 	} *watching;
 	unsigned int watch_idx;
@@ -719,6 +720,26 @@ int pv_watchfd_loop(pvstate_t state)
 	struct timespec next_update, next_remotecheck, cur_time;
 	int prev_displayed_lines, blank_lines;
 
+	/*
+	 * TODO: new logic:
+	 * For each watching[] item, "pid_last_seen" stops being updated
+	 * when the PID ceases to exist.  If "fd" is >=0 then
+	 * "pid_last_seen" is set to the newest of the "fd_last_seen" values
+	 * of the info_array[] fd info items.  When "pid_last_seen" is too
+	 * old, "finished" becomes true so this watching[] item stops being
+	 * displayed.
+	 *
+	 * In each watching[].info_array[] fd info item, once its "watch_fd"
+	 * is closed, its "fd_last_seen" stops being updated, and once
+	 * that's stopped updating long enough, its "unused" becomes true.
+	 *
+	 * All of this allows information to be held on-screen for a short
+	 * while after the fd closes or the PID exits (#81).
+	 */
+
+	/* TODO: implement the above (pid_last_seen, fd_last_seen) */
+	/* TODO: check whether pid_last_seen is needed, or only fd_last_seen */
+
 	/* If there's nothing to watch, do nothing at all. */
 	if (state->watchfd.count < 1)
 		return 0;