Retain fast arrow switches

Update equipment data to make fast arrow switching permanent
(fixes #76)

This also makes it clearer what the current arrow type is.

Thanks to @PhlexPlexico for help and the initial implementation!

source/game/common_data.h

@@ -40,12 +40,15 @@ struct __attribute__((packed)) __attribute__((aligned(2))) PlayerData {
 static_assert(sizeof(PlayerData) == 0x32);
 static_assert(rst::util::OffsetOf(&PlayerData::magic) == 0x1F);
 
-struct FormEquipmentData {
-  ItemId item_btn_b;
-  ItemId item_btn_y;
-  ItemId item_btn_x;
-  ItemId item_btn_i;
-  ItemId item_btn_ii;
+union FormEquipmentData {
+  std::array<ItemId, 5> item_btns;
+  struct {
+    ItemId item_btn_b;
+    ItemId item_btn_y;
+    ItemId item_btn_x;
+    ItemId item_btn_i;
+    ItemId item_btn_ii;
+  };
 };
 
 struct EquipmentData {

source/game/player.h

@@ -158,7 +158,7 @@ struct Player : public Actor {
 
   char field_1F8;
   FormParamIndex form_param_idx;
-  char field_1FA;
+  u8 item_btn_slot;
   Action current_action;
   ItemId held_item;
   FormParamIndex form_param_idx2;

source/rst/link.cpp

@@ -211,6 +211,8 @@ void HandleFastArrowSwitch(game::act::Player* player) {
     } while (!can_use_arrow(idx));
 
     s_fast_arrow_state.override_action = static_cast<game::Action>(idx + first);
+    player->current_action = player->action = *s_fast_arrow_state.override_action;
+    cdata.save.equipment.data[0].item_btns[player->item_btn_slot] = s_arrow_types[idx].required_item;
     util::Print("%s: override_action is now %u (%s)", __func__,
                 u8(*s_fast_arrow_state.override_action), s_arrow_types[idx].name);