Extend the mode-mouse option to add a third choice which means the mouse

does not enter copy mode. Patch from SF bug 3374493.

In future the mode-mouse option is likely to die and be broken into
several smaller options.

input-keys.c

@@ -204,6 +204,7 @@ input_mouse(struct window_pane *wp, struct mouse_event *m)
 {
 	char	buf[10];
 	size_t	len;
+	int	value;
 
 	if (wp->screen->mode & ALL_MOUSE_MODES) {
 		if (wp->screen->mode & MODE_MOUSE_UTF8) {
@@ -221,7 +222,8 @@ input_mouse(struct window_pane *wp, struct mouse_event *m)
 		}
 		bufferevent_write(wp->event, buf, len);
 	} else if ((m->b & MOUSE_BUTTON) != MOUSE_2) {
-		if (options_get_number(&wp->window->options, "mode-mouse") &&
+		value = options_get_number(&wp->window->options, "mode-mouse");
+		if (value == 1 &&
 		    window_pane_set_mode(wp, &window_copy_mode) == 0) {
 			window_copy_init_from_pane(wp);
 			if (wp->mode->mouse != NULL)

options-table.c

@@ -36,6 +36,9 @@
 const char *options_table_mode_keys_list[] = {
 	"emacs", "vi", NULL
 };
+const char *options_table_mode_mouse_list[] = {
+	"off", "on", "copy-mode", NULL
+};
 const char *options_table_clock_mode_style_list[] = {
 	"12", "24", NULL
 };
@@ -484,7 +487,8 @@ const struct options_table_entry window_options_table[] = {
 	},
 
 	{ .name = "mode-mouse",
-	  .type = OPTIONS_TABLE_FLAG,
+	  .type = OPTIONS_TABLE_CHOICE,
+	  .choices = options_table_mode_mouse_list,
 	  .default_num = 0
 	},
 

tmux.1

@@ -2358,12 +2358,17 @@ contains
 .Ql vi .
 .Pp
 .It Xo Ic mode-mouse
-.Op Ic on | off
+.Op Ic on | off | copy-mode
 .Xc
 Mouse state in modes.
 If on, the mouse may be used to enter copy mode and copy a selection by
 dragging, to enter copy mode and scroll with the mouse wheel, or to select an
 option in choice mode.
+If set to
+.Em
+copy-mode ,
+the mouse behaves as set to on, but cannot be used to enter copy
+mode.
 .Pp
 .It Xo Ic monitor-activity
 .Op Ic on | off