renderer: add transformers

src/Window.hpp

@@ -32,6 +32,8 @@ enum eGroupRules
     GROUP_OVERRIDE    = 1 << 6, // Override other rules
 };
 
+class IWindowTransformer;
+
 template <typename T>
 class CWindowOverridableVar {
   public:
@@ -290,6 +292,9 @@ class CWindow {
     SWindowSpecialRenderData    m_sSpecialRenderData;
     SWindowAdditionalConfigData m_sAdditionalConfigData;
 
+    // Transformers
+    std::vector<std::unique_ptr<IWindowTransformer>> m_vTransformers;
+
     // for alpha
     CAnimatedVariable m_fActiveInactiveAlpha;