Don’t start i3-nagbar when using -C to validate the config

include/i3.h

@@ -44,5 +44,6 @@ extern uint8_t root_depth;
 extern bool xcursor_supported, xkb_supported;
 extern xcb_window_t root;
 extern struct ev_loop *main_loop;
+extern bool only_check_config;
 
 #endif

src/cfgparse.y

@@ -266,7 +266,10 @@ static void nagbar_cleanup(EV_P_ ev_cleanup *watcher, int revent) {
  *
  */
 static void start_configerror_nagbar(const char *config_path) {
-    fprintf(stderr, "Would start i3-nagscreen now\n");
+    if (only_check_config)
+        return;
+
+    fprintf(stderr, "Starting i3-nagbar due to configuration errors\n");
     configerror_pid = fork();
     if (configerror_pid == -1) {
         warn("Could not fork()");

src/main.c

@@ -61,6 +61,11 @@ struct ws_assignments_head ws_assignments = TAILQ_HEAD_INITIALIZER(ws_assignment
 bool xcursor_supported = true;
 bool xkb_supported = true;
 
+/* This will be set to true when -C is used so that functions can behave
+ * slightly differently. We don’t want i3-nagbar to be started when validating
+ * the config, for example. */
+bool only_check_config = false;
+
 /*
  * This callback is only a dummy, see xcb_prepare_cb and xcb_check_cb.
  * See also man libev(3): "ev_prepare" and "ev_check" - customise your event loop
@@ -194,7 +199,6 @@ int main(int argc, char *argv[]) {
     bool autostart = true;
     char *layout_path = NULL;
     bool delete_layout_path = false;
-    bool only_check_config = false;
     bool force_xinerama = false;
     bool disable_signalhandler = false;
     static struct option long_options[] = {