#5584: Purge any shaders that have not been used the last frame, to p…

…revent introducing a long-running memory leak.

Re-using the CamRenderer container memory reduces the time needed to render 100 frames from 8.7 to 7.7 seconds.

libs/render/CamRenderer.h

@@ -104,9 +104,17 @@ class CamRenderer :
     {
         // Keep the shader map intact, but clear the renderables vectors,
         // so that we don't have to re-allocate the whole memory every frame
-        for (auto& pair : _litRenderables)
+        // Purge the ones that have not been used in this render round
+        for (auto i = _litRenderables.begin(); i != _litRenderables.end();)
         {
-            pair.second.clear();
+            if (i->second.empty())
+            {
+                // This shader has not been used at all in the last frame, free the memory
+                _litRenderables.erase(i++);
+                continue;
+            }
+
+            (i++)->second.clear();
         }
 
         _sceneLights.clear();