From dc3fdc8dc7c45fc4924ee4eeb8b6c7c6a80e41f1 Mon Sep 17 00:00:00 2001
From: Nicholas Marriott <nicm@openbsd.org>
Date: Wed, 28 Oct 2009 22:53:14 +0000
Subject: [PATCH] If any client currently displaying a window pane has more
 than 1 KB of output buffered, don't accept any further data from the process
 running in the pane.

This makes tmux much more responsive when flooded with output, although other
buffers can still have an impact when running remotely.

Prompted by a query from Ranganathan Sankaralingam.
---
 server-window.c | 27 ++++++++++++++++++++++++++-
 tmux.h          |  3 +++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/server-window.c b/server-window.c
index 969395c8..122ca092 100644
--- a/server-window.c
+++ b/server-window.c
@@ -22,6 +22,7 @@
 
 #include "tmux.h"
 
+int	server_window_backoff(struct window_pane *);
 int	server_window_check_bell(struct session *, struct window *);
 int	server_window_check_activity(struct session *, struct window *);
 int	server_window_check_content(
@@ -44,7 +45,9 @@ server_window_prepare(void)
 		TAILQ_FOREACH(wp, &w->panes, entry) {	
 			if (wp->fd == -1)
 				continue;
-			events = POLLIN;
+			events = 0;
+			if (!server_window_backoff(wp))
+				events |= POLLIN;
 			if (BUFFER_USED(wp->out) > 0)
 				events |= POLLOUT;
 			server_poll_add(
@@ -61,6 +64,28 @@ server_window_prepare(void)
 	}
 }
 
+/* Check if this window should suspend reading. */
+int
+server_window_backoff(struct window_pane *wp)
+{
+	struct client	*c;
+	u_int		 i;
+
+	if (!window_pane_visible(wp))
+		return (0);
+
+	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
+		c = ARRAY_ITEM(&clients, i);
+		if (c == NULL || c->session == NULL)
+			continue;
+		if (c->session->curw->window != wp->window)
+			continue;
+		if (BUFFER_USED(c->tty.out) > BACKOFF_THRESHOLD)
+			return (1);
+	}
+	return (0);
+}
+
 /* Process a single window pane event. */
 void
 server_window_callback(int fd, int events, void *data)
diff --git a/tmux.h b/tmux.h
index e270e821..41ace3a8 100644
--- a/tmux.h
+++ b/tmux.h
@@ -65,6 +65,9 @@ extern char   **environ;
 /* Maximum poll timeout (when attached). */
 #define POLL_TIMEOUT 50
 
+/* Maximum data to buffer for output before suspending reading from panes. */
+#define BACKOFF_THRESHOLD 1024
+
 /*
  * Maximum sizes of strings in message data. Don't forget to bump
  * PROTOCOL_VERSION if any of these change!