diff --git a/include/drmdisplaycompositor.h b/include/drmdisplaycompositor.h
index cfd8f4a..26e2572 100644
--- a/include/drmdisplaycompositor.h
+++ b/include/drmdisplaycompositor.h
@@ -50,6 +50,8 @@
   kConcurrent
 };
 
+std::ostream &operator<<(std::ostream &str, FlatteningState state);
+
 class DrmDisplayCompositor {
  public:
   DrmDisplayCompositor();
@@ -77,6 +79,7 @@
   }
 
   FlatteningState GetFlatteningState() const;
+  uint32_t GetFlattenedFramesCount() const;
   bool ShouldFlattenOnClient() const;
 
   std::tuple<uint32_t, uint32_t, int> GetActiveModeResolution();
@@ -108,6 +111,7 @@
   void ApplyFrame(std::unique_ptr<DrmDisplayComposition> composition,
                   int status, bool writeback = false);
 
+  void SetFlattening(FlatteningState new_state);
   bool IsFlatteningNeeded() const;
   int FlattenActiveComposition();
   int FlattenOnClient();
@@ -148,6 +152,7 @@
   int writeback_fence_;
 
   FlatteningState flattening_state_;
+  uint32_t frames_flattened_;
 
   std::function<void(int)> refresh_display_cb_;
 };
diff --git a/include/drmhwctwo.h b/include/drmhwctwo.h
index 43f1fce..2bbe334 100644
--- a/include/drmhwctwo.h
+++ b/include/drmhwctwo.h
@@ -260,9 +260,11 @@
     struct Stats {
       Stats minus(Stats b) {
         return {total_frames_ - b.total_frames_,
-                total_pixops_ - b.total_pixops_, gpu_pixops_ - b.gpu_pixops_,
+                total_pixops_ - b.total_pixops_,
+                gpu_pixops_ - b.gpu_pixops_,
                 failed_kms_validate_ - b.failed_kms_validate_,
-                failed_kms_present_ - b.failed_kms_present_};
+                failed_kms_present_ - b.failed_kms_present_,
+                frames_flattened_ - b.frames_flattened_};
       }
 
       uint32_t total_frames_ = 0;
@@ -270,6 +272,7 @@
       uint64_t gpu_pixops_ = 0;
       uint32_t failed_kms_validate_ = 0;
       uint32_t failed_kms_present_ = 0;
+      uint32_t frames_flattened_ = 0;
     } total_stats_, prev_stats_;
     std::string DumpDelta(DrmHwcTwo::HwcDisplay::Stats delta);
   };