Add config flag to persist GUI visibility state at samuncle's request

src/config/user_config.hpp

@@ -926,6 +926,10 @@ namespace UserConfigParams
             PARAM_DEFAULT( BoolUserConfigParam(false, "artist_debug_mode",
                                "Whether to enable track debugging features") );
 
+    PARAM_PREFIX BoolUserConfigParam        m_hide_gui
+        PARAM_DEFAULT(BoolUserConfigParam(false, "debug_hide_gui",
+            "Whether to hide the GUI (artist debug mode)"));
+
     PARAM_PREFIX BoolUserConfigParam        m_everything_unlocked
             PARAM_DEFAULT( BoolUserConfigParam(false, "everything_unlocked",
                                "Enable all karts and tracks") );

src/states_screens/race_gui.cpp

@@ -65,6 +65,9 @@ RaceGUI::RaceGUI()
 {
     m_enabled = true;
     
+    if (UserConfigParams::m_artist_debug_mode && UserConfigParams::m_hide_gui)
+        m_enabled = false;
+
     // Determine maximum length of the rank/lap text, in order to
     // align those texts properly on the right side of the viewport.
     gui::ScalableFont* font = GUIEngine::getHighresDigitFont();

src/states_screens/race_gui_overworld.cpp

@@ -73,6 +73,10 @@ const int COMPLETED_HARD = 4;
 RaceGUIOverworld::RaceGUIOverworld()
 {
     m_enabled = true;
+
+    if (UserConfigParams::m_artist_debug_mode && UserConfigParams::m_hide_gui)
+        m_enabled = false;
+
     m_is_first_render_call = true;
     m_close_to_a_challenge = false;
     m_current_challenge = NULL;