transformers: allow modifying renderdata pre-pass

src/render/Transformer.hpp

@@ -2,12 +2,19 @@
 
 #include "Framebuffer.hpp"
 
+struct SRenderData;
+
 // A window transformer can be attached to a window.
 // If any is attached, Hyprland will render the window to a separate fb, then call the transform() func with it,
 // and finally render it back to the main fb after all transformers pass.
+//
+// Worth noting transformers for now only affect the main pass (not popups)
 class IWindowTransformer {
   public:
     // called by Hyprland. For more data about what is being rendered, inspect render data.
     // returns the out fb.
     virtual CFramebuffer* transform(CFramebuffer* in) = 0;
+
+    // called by Hyprland before a window main pass is started.
+    virtual void preWindowRender(SRenderData* pRenderData);
 };