Copy mode needs to keep the original grid intact so it can copy from it

if needed, so it disables reading from the pane. This can be problem
with some programs. So make tmux automatically exit all modes after 180
seconds of inactivity and if there is pending output.

tmux.h

@@ -823,6 +823,7 @@ struct window_mode {
 	void	(*key)(struct window_pane *, struct client *, struct session *,
 		    key_code, struct mouse_event *);
 };
+#define WINDOW_MODE_TIMEOUT 180
 
 /* Structures for choose mode. */
 struct window_choose_data {
@@ -905,6 +906,8 @@ struct window_pane {
 
 	const struct window_mode *mode;
 	void		*modedata;
+	struct event	 modetimer;
+	time_t		 modelast;
 
 	TAILQ_ENTRY(window_pane) entry;
 	RB_ENTRY(window_pane) tree_entry;

window.c

@@ -17,6 +17,7 @@
  */
 
 #include <sys/types.h>
+#include <sys/ioctl.h>
 
 #include <errno.h>
 #include <fcntl.h>
@@ -1046,15 +1047,38 @@ window_pane_alternate_off(struct window_pane *wp, struct grid_cell *gc,
 	wp->flags |= PANE_REDRAW;
 }
 
+static void
+window_pane_mode_timer(__unused int fd, __unused short events, void *arg)
+{
+	struct window_pane	*wp = arg;
+	struct timeval		 tv = { .tv_sec = 10 };
+	int			 n = 0;
+
+	evtimer_del(&wp->modetimer);
+	evtimer_add(&wp->modetimer, &tv);
+
+	log_debug("%%%u in mode: last=%ld", wp->id, (long)wp->modelast);
+
+	if (wp->modelast < time(NULL) - WINDOW_MODE_TIMEOUT) {
+		if (ioctl(wp->fd, FIONREAD, &n) == -1 || n > 0)
+			window_pane_reset_mode(wp);
+	}
+}
+
 int
 window_pane_set_mode(struct window_pane *wp, const struct window_mode *mode)
 {
 	struct screen	*s;
+	struct timeval	 tv = { .tv_sec = 10 };
 
 	if (wp->mode != NULL)
 		return (1);
 	wp->mode = mode;
 
+	wp->modelast = time(NULL);
+	evtimer_set(&wp->modetimer, window_pane_mode_timer, wp);
+	evtimer_add(&wp->modetimer, &tv);
+
 	if ((s = wp->mode->init(wp)) != NULL)
 		wp->screen = s;
 	wp->flags |= (PANE_REDRAW|PANE_CHANGED);
@@ -1069,6 +1093,8 @@ window_pane_reset_mode(struct window_pane *wp)
 	if (wp->mode == NULL)
 		return;
 
+	evtimer_del(&wp->modetimer);
+
 	wp->mode->free(wp);
 	wp->mode = NULL;
 
@@ -1088,6 +1114,7 @@ window_pane_key(struct window_pane *wp, struct client *c, struct session *s,
 		return;
 
 	if (wp->mode != NULL) {
+		wp->modelast = time(NULL);
 		if (wp->mode->key != NULL)
 			wp->mode->key(wp, c, s, key, m);
 		return;