Refactor/main menu (#416)

* Add basic common_ui background gfx functions

* Move game main menu to separate file

* clang format

* tmp commit basic docs

* clang format

* scope vars and cleanup

* Quick consistency update. Finalize.

This branch is based on: https://github.com/GBALATRO/balatro-gba/pull/363
Co-authored-by: emiyl <me@emiyl.com>

* Simplify global struct

* clang-format

* Add clang-format to subdirs

* Move timer definitions into their own file

* clang-format

* Fix action yml

* docs

* Update for PR

* Move game start to a state

* Remove lag switch

* Remove GameVariables pointer for callbacks

* Make game_vars a global

* move declaration of game vars in header

* Fix multiple game_vars

* fix for pr

* remove change_background in update again

* clang format

* Make bgCallbacks table static const

---------

Co-authored-by: emiyl <me@emiyl.com>

source/game/common_ui.c

@@ -1,22 +1,32 @@
 #include "game/common_ui.h"
 
 #include "game.h"
+#include "game/main_menu.h"
 
 typedef void (*BackgroundRenderCallback)(void);
 
+static enum BackgroundId background = BG_NONE;
+
 // Map to fill in for refactor
-BackgroundRenderCallback bgCallbacks[] =
-{
+static const BackgroundRenderCallback bgCallbacks[] = {
     [BG_NONE] = NULL,
     [BG_CARD_SELECTING] = NULL,
     [BG_CARD_PLAYING] = NULL,
     [BG_ROUND_END] = NULL,
     [BG_SHOP] = NULL,
     [BG_BLIND_SELECT] = NULL,
-    [BG_MAIN_MENU] = NULL,
+    [BG_MAIN_MENU] = game_main_menu_change_background,
 };
 
 void change_background(enum BackgroundId id)
 {
+    if (id == BG_MAIN_MENU)
+    {
+        if (id != background)
+        {
+            bgCallbacks[id]();
+        }
+    }
     change_background_legacy(id);
+    background = id;
 }