1 files changed, 114 insertions, 0 deletions
diff --git a/gfx/layers/composite/FPSCounter.h b/gfx/layers/composite/FPSCounter.h
new file mode 100644
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+++ b/gfx/layers/composite/FPSCounter.h
@@ -0,0 +1,114 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layers_opengl_FPSCounter_h_
+#define mozilla_layers_opengl_FPSCounter_h_
+
+#include <algorithm>                    // for min
+#include <stddef.h>                     // for size_t
+#include <map>                          // for std::map
+#include "GLDefs.h"                     // for GLuint
+#include "mozilla/RefPtr.h"             // for already_AddRefed, RefCounted
+#include "mozilla/TimeStamp.h"          // for TimeStamp, TimeDuration
+#include "nsTArray.h"                   // for AutoTArray, nsTArray_Impl, etc
+#include "prio.h"                       // for NSPR file i/o
+
+namespace mozilla {
+namespace layers {
+
+class DataTextureSource;
+class Compositor;
+
+// Dump the FPS histogram every 10 seconds or kMaxFrameFPS
+const int kFpsDumpInterval = 10;
+
+// On desktop, we can have 240 hz monitors, so 10 seconds
+// times 240 frames = 2400
+const int kMaxFrames = 2400;
+
+/**
+ * The FPSCounter tracks how often we composite or have a layer transaction.
+ * At each composite / layer transaction, we record the timestamp.
+ * After kFpsDumpInterval number of composites / transactions, we calculate
+ * the average and standard deviation of frames composited. We dump a histogram,
+ * which allows for more statistically significant measurements. We also dump
+ * absolute frame composite times to a file on the device.
+ * The FPS counters displayed on screen are based on how many frames we
+ * composited within the last ~1 second. The more accurate measurement is to
+ * grab the histogram from stderr or grab the FPS timestamp dumps written to file.
+ *
+ * To enable dumping to file, enable
+ * layers.acceleration.draw-fps.write-to-file pref.
+
+  double AddFrameAndGetFps(TimeStamp aCurrentFrame) {
+    AddFrame(aCurrentFrame);
+    return EstimateFps(aCurrentFrame);
+  }
+ * To enable printing histogram data to logcat,
+ * enable layers.acceleration.draw-fps.print-histogram
+ *
+ * Use the HasNext(), GetNextTimeStamp() like an iterator to read the data,
+ * backwards in time. This abstracts away the mechanics of reading the data.
+ */
+class FPSCounter {
+public:
+  explicit FPSCounter(const char* aName);
+  ~FPSCounter();
+
+  void AddFrame(TimeStamp aTimestamp);
+  double AddFrameAndGetFps(TimeStamp aTimestamp);
+  double GetFPS(TimeStamp aTimestamp);
+
+private:
+  void      Init();
+  bool      CapturedFullInterval(TimeStamp aTimestamp);
+
+  // Used while iterating backwards over the data
+  void      ResetReverseIterator();
+  bool      HasNext(TimeStamp aTimestamp, double aDuration = kFpsDumpInterval);
+  TimeStamp GetNextTimeStamp();
+  int       GetLatestReadIndex();
+  TimeStamp GetLatestTimeStamp();
+  void      WriteFrameTimeStamps(PRFileDesc* fd);
+  bool      IteratedFullInterval(TimeStamp aTimestamp, double aDuration);
+
+  void      PrintFPS();
+  int       BuildHistogram(std::map<int, int>& aHistogram);
+  void      PrintHistogram(std::map<int, int>& aHistogram);
+  double    GetMean(std::map<int,int> aHistogram);
+  double    GetStdDev(std::map<int, int> aHistogram);
+  nsresult  WriteFrameTimeStamps();
+
+  /***
+   * mFrameTimestamps is a psuedo circular buffer
+   * Since we have a constant write time and don't
+   * read at an offset except our latest write
+   * we don't need an explicit read pointer.
+   */
+  AutoTArray<TimeStamp, kMaxFrames> mFrameTimestamps;
+  int mWriteIndex;      // points to next open write slot
+  int mIteratorIndex;   // used only when iterating
+  const char* mFPSName;
+  TimeStamp mLastInterval;
+};
+
+struct FPSState {
+  FPSState();
+  void DrawFPS(TimeStamp, int offsetX, int offsetY, unsigned, Compositor* aCompositor);
+  void NotifyShadowTreeTransaction() {
+    mTransactionFps.AddFrame(TimeStamp::Now());
+  }
+
+  FPSCounter mCompositionFps;
+  FPSCounter mTransactionFps;
+
+private:
+  RefPtr<DataTextureSource> mFPSTextureSource;
+};
+
+} // namespace layers
+} // namespace mozilla
+
+#endif // mozilla_layers_opengl_FPSCounter_h_