New option, mouse-select-pane. If on, the mouse may be used to select the

current pane.

Suggested by sthen@ and also by someone else ages ago who I have forgotten.

cmd-set-option.c

@@ -67,6 +67,7 @@ const struct set_option_entry set_option_table[] = {
 	{ "message-attr", SET_OPTION_ATTRIBUTES, 0, 0, NULL },
 	{ "message-bg", SET_OPTION_COLOUR, 0, 0, NULL },
 	{ "message-fg", SET_OPTION_COLOUR, 0, 0, NULL },
+	{ "mouse-select-pane", SET_OPTION_FLAG, 0, 0, NULL },
 	{ "prefix", SET_OPTION_KEYS, 0, 0, NULL },
 	{ "repeat-time", SET_OPTION_NUMBER, 0, SHRT_MAX, NULL },
 	{ "set-remain-on-exit", SET_OPTION_FLAG, 0, 0, NULL },

server.c

@@ -825,6 +825,7 @@ server_handle_client(struct client *c)
 	struct window		*w;
 	struct window_pane	*wp;
 	struct screen		*s;
+	struct options		*oo;
 	struct timeval	 	 tv;
 	struct key_binding	*bd;
 	struct keylist		*keylist;
@@ -849,6 +850,7 @@ server_handle_client(struct client *c)
 		c->session->activity = time(NULL);
 		w = c->session->curw->window;
 		wp = w->active;	/* could die */
+		oo = &c->session->options;
 
 		/* Special case: number keys jump to pane in identify mode. */
 		if (c->flags & CLIENT_IDENTIFY && key >= '0' && key <= '9') {	
@@ -868,6 +870,10 @@ server_handle_client(struct client *c)
 
 		/* Check for mouse keys. */
 		if (key == KEYC_MOUSE) {
+			if (options_get_number(oo, "mouse-select-pane")) {
+				window_set_active_at(w, mouse[1], mouse[2]);
+				wp = w->active;
+			}
 			window_pane_mouse(wp, c, mouse[0], mouse[1], mouse[2]);
 			continue;
 		}
@@ -935,7 +941,9 @@ server_handle_client(struct client *c)
 	}
 	if (c->session == NULL)
 		return;
-	wp = c->session->curw->window->active;	/* could die - do each loop */
+	w = c->session->curw->window;
+	wp = w->active;
+	oo = &c->session->options;
 	s = wp->screen;
 
 	/*
@@ -948,7 +956,7 @@ server_handle_client(struct client *c)
 	 * tty_region/tty_reset/tty_update_mode already take care of not
 	 * resetting things that are already in their default state.
 	 */
-	status = options_get_number(&c->session->options, "status");
+	status = options_get_number(oo, "status");
 	tty_region(&c->tty, 0, c->tty.sy - 1, 0);
 	if (!window_pane_visible(wp) || wp->yoff + s->cy >= c->tty.sy - status)
 		tty_cursor(&c->tty, 0, 0, 0, 0);
@@ -956,6 +964,9 @@ server_handle_client(struct client *c)
 		tty_cursor(&c->tty, s->cx, s->cy, wp->xoff, wp->yoff);
 
 	mode = s->mode;
+	if (TAILQ_NEXT(TAILQ_FIRST(&w->panes), entry) != NULL &&
+	    options_get_number(oo, "mouse-select-pane"))
+		mode |= MODE_MOUSE;
 	tty_update_mode(&c->tty, mode);
 	tty_reset(&c->tty);
 }

tmux.1

@@ -1292,7 +1292,7 @@ with
 .Op Ic on | off
 .Xc
 If this option is
-.Ic on 
+.Ic on
 (the default),
 instead of each session locking individually as each has been
 idle for
@@ -1336,6 +1336,14 @@ from the 256-colour palette, or
 .Ic default .
 .It Ic message-fg Ar colour
 Set status line message foreground colour.
+.It Xo Ic mouse-select-pane
+.Op Ic on | off
+.Xc
+If on,
+.Nm
+captures the mouse and when a window is split into multiple panes the mouse may
+be used to select the current pane.
+The mouse click is also passed through to the application as normal.
 .It Ic prefix Ar keys
 Set the keys accepted as a prefix key.
 .Ar keys

tmux.c

@@ -381,6 +381,7 @@ main(int argc, char **argv)
 	options_set_number(so, "message-attr", 0);
 	options_set_number(so, "message-bg", 3);
 	options_set_number(so, "message-fg", 0);
+	options_set_number(so, "mouse-select-pane", 0);
 	options_set_number(so, "repeat-time", 500);
 	options_set_number(so, "set-remain-on-exit", 0);
 	options_set_number(so, "set-titles", 0);

tmux.h

@@ -1648,6 +1648,7 @@ struct window	*window_create(const char *, const char *, const char *,
 		     const char *, struct environ *, struct termios *,
     		     u_int, u_int, u_int, char **);
 void		 window_destroy(struct window *);
+void		 window_set_active_at(struct window *, u_int, u_int);
 void		 window_set_active_pane(struct window *, struct window_pane *);
 struct window_pane *window_add_pane(struct window *, u_int);
 void		 window_resize(struct window *, u_int, u_int);

window.c

@@ -304,6 +304,23 @@ window_set_active_pane(struct window *w, struct window_pane *wp)
 	}
 }
 
+void
+window_set_active_at(struct window *w, u_int x, u_int y)
+{
+	struct window_pane	*wp;
+
+	TAILQ_FOREACH(wp, &w->panes, entry) {
+		if (!window_pane_visible(wp))
+			continue;
+		if (x < wp->xoff || x >= wp->xoff + wp->sx)
+			continue;
+		if (y < wp->yoff || y >= wp->yoff + wp->sy)
+			continue;
+		window_set_active_pane(w, wp);
+		break;
+	}
+}
+
 struct window_pane *
 window_add_pane(struct window *w, u_int hlimit)
 {