From beef890122f4ac7040d51dd17dba292d32f76a66 Mon Sep 17 00:00:00 2001
From: Chinmay Garde <chinmaygarde@google.com>
Date: Wed, 30 Sep 2015 14:47:57 -0700
Subject: [PATCH] Flip the stats graph and handle boundary conditions

---
 sky/compositor/instrumentation.cc  | 21 +++++++++++++++------
 sky/compositor/statistics_layer.cc |  1 -
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/sky/compositor/instrumentation.cc b/sky/compositor/instrumentation.cc
index 8d492dde328..6738489a7b6 100644
--- a/sky/compositor/instrumentation.cc
+++ b/sky/compositor/instrumentation.cc
@@ -27,6 +27,10 @@ void Stopwatch::stop() {
   _laps[_current_sample] = _lastLap;
 }
 
+static inline constexpr double UnitFrameInterval(double frameTimeMS) {
+  return frameTimeMS * 60.0 * 1e-3;
+}
+
 void Stopwatch::visualize(SkCanvas& canvas, const SkRect& rect) const {
   SkAutoCanvasRestore save(&canvas, false);
 
@@ -41,14 +45,19 @@ void Stopwatch::visualize(SkCanvas& canvas, const SkRect& rect) const {
   auto width = rect.width();
   auto height = rect.height();
 
-  path.moveTo(0, 0);
-  path.lineTo(0, height * (_laps[0].InMillisecondsF() / 16.0));
+  auto unitHeight = (1.0 - UnitFrameInterval(_laps[0].InMillisecondsF()));
+
+  path.moveTo(0, height);
+  path.lineTo(0, height * unitHeight);
+
   for (size_t i = 0; i < kMaxSamples; i++) {
-    path.lineTo(width * (static_cast<double>(i) / kMaxSamples),
-                height * (_laps[i].InMillisecondsF() / 16.0));
+    double unitWidth = (static_cast<double>(i + 1) / kMaxSamples);
+    unitHeight = (1.0 - UnitFrameInterval(_laps[i].InMillisecondsF()));
+    path.lineTo(width * unitWidth, height * unitHeight);
   }
-  path.lineTo(width, 0);
-  path.lineTo(0, 0);
+
+  path.lineTo(width, height);
+
   path.close();
 
   paint.setColor(0xAA0000FF);
diff --git a/sky/compositor/statistics_layer.cc b/sky/compositor/statistics_layer.cc
index 5823683c350..d8486cb553f 100644
--- a/sky/compositor/statistics_layer.cc
+++ b/sky/compositor/statistics_layer.cc
@@ -39,7 +39,6 @@ void StatisticsLayer::Paint(PaintContext::ScopedFrame& frame) {
   }
 
   if (options_.isEnabled(CompositorOptions::Option::DisplayFrameStatistics)) {
-    // Frame (2032): 3.26ms
     double msPerFrame = context.frame_time().lastLap().InMillisecondsF();
     double fps = 1e3 / msPerFrame;