transformers: allow modifying renderdata pre-pass

src/render/Renderer.cpp

@@ -412,9 +412,14 @@ void CHyprRenderer::renderWindow(CWindow* pWindow, CMonitor* pMonitor, timespec*
 
         const bool TRANSFORMERSPRESENT = !pWindow->m_vTransformers.empty();
 
-        if (TRANSFORMERSPRESENT)
+        if (TRANSFORMERSPRESENT) {
             g_pHyprOpenGL->bindOffMain();
 
+            for (auto& t : pWindow->m_vTransformers) {
+                t->preWindowRender(&renderdata);
+            }
+        }
+
         if (!pWindow->m_bIsFullscreen || PWORKSPACE->m_efFullscreenMode != FULLSCREEN_FULL)
             for (auto& wd : pWindow->m_dWindowDecorations)
                 wd->draw(pMonitor, renderdata.alpha * renderdata.fadeAlpha, offset);

src/render/Transformer.cpp

@@ -1 +1,5 @@
 #include "Transformer.hpp"
+
+void IWindowTransformer::preWindowRender(SRenderData* pRenderData) {
+    ;
+}

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);
 };