ksys/gdt: Add common flags

src/KingSystem/GameData/CMakeLists.txt

@@ -1,7 +1,10 @@
 target_sources(uking PRIVATE
+  gdtCommonFlags.cpp
+  gdtCommonFlags.h
   gdtFlag.cpp
   gdtFlag.h
   gdtFlagProxy.h
+  gdtFlagUtils.h
   gdtManager.cpp
   gdtManager.h
   gdtSaveMgr.cpp

src/KingSystem/GameData/gdtFlagUtils.h

@@ -0,0 +1,5 @@
+#pragma once
+
+#include "KingSystem/GameData/gdtManager.h"
+
+namespace ksys::gdt {}  // namespace ksys::gdt

src/KingSystem/GameData/gdtManager.h

@@ -22,6 +22,8 @@ namespace ksys::gdt {
 
 enum class FlagHandle : u32 {};
 
+constexpr FlagHandle InvalidHandle = FlagHandle(-1);
+
 class TriggerParamRef {
 public:
     TriggerParamRef(TriggerParam** param_1, TriggerParam** param, bool check_permissions,