Performance Overlay fixes

- fix dartdocs for addPerformanceOverlay
- make PerformanceOverlayLayer honour its x, y, and height.
- fix the y axis of PerformanceOverlayLayer to only show 3x16ms, since
  if it's more than 16ms it really doesn't matter what it is.
- make the label on the PerformanceOverlayLayer show the worst time on
  record not the instantaneous time.
- pin the fps to a maximum of 60Hz

flow/instrumentation.cc

@@ -13,7 +13,6 @@ namespace instrumentation {
 
 static const size_t kMaxSamples = 120;
 static const size_t kMaxFrameMarkers = 8;
-static const double kOneFrameMS = 1e3 / 60.0;
 
 Stopwatch::Stopwatch() : _start(base::TimeTicks::Now()), _current_sample(0) {
   const base::TimeDelta delta;
@@ -42,6 +41,13 @@ static inline constexpr double UnitFrameInterval(double frameTimeMS) {
   return frameTimeMS * 60.0 * 1e-3;
 }
 
+static inline double UnitHeight(double frameTimeMS, double maxUnitInterval) {
+  double unitHeight = UnitFrameInterval(frameTimeMS) / maxUnitInterval;
+  if (unitHeight > 1.0)
+    unitHeight = 1.0;
+  return unitHeight;
+}
+
 base::TimeDelta Stopwatch::maxDelta() const {
   base::TimeDelta maxDelta;
   for (size_t i = 0; i < kMaxSamples; i++) {
@@ -55,52 +61,53 @@ base::TimeDelta Stopwatch::maxDelta() const {
 void Stopwatch::visualize(SkCanvas& canvas, const SkRect& rect) const {
   SkPaint paint;
 
-  // Paint the background
-  paint.setColor(0xAAFFFFFF);
+  // Paint the background.
+  paint.setColor(0x99FFFFFF);
   canvas.drawRect(rect, paint);
 
-  // Paint the graph
-  SkPath path;
+  // Establish the graph position.
+  const SkScalar x = rect.x();
+  const SkScalar y = rect.y();
   const SkScalar width = rect.width();
   const SkScalar height = rect.height();
+  const SkScalar bottom = y + height;
+  const SkScalar right = x + width;
 
-  // Find the max delta. We use this to scale the graph
-
-  double maxInterval = maxDelta().InMillisecondsF();
-
-  if (maxInterval < kOneFrameMS) {
-    maxInterval = kOneFrameMS;
-  } else {
-    maxInterval =
-        kOneFrameMS * (static_cast<size_t>(maxInterval / kOneFrameMS) + 1);
-  }
-
+  // Scale the graph to show frame times up to those that are 4 times the frame time.
+  const double maxInterval = kOneFrameMS * 3.0;
   const double maxUnitInterval = UnitFrameInterval(maxInterval);
 
-  // Draw the path
-  double unitHeight =
-      UnitFrameInterval(_laps[0].InMillisecondsF()) / maxUnitInterval;
-
-  path.moveTo(0, height);
-  path.lineTo(0, height * (1.0 - unitHeight));
-
-  for (size_t i = 0; i < kMaxSamples; i++) {
-    double unitWidth = (static_cast<double>(i + 1) / kMaxSamples);
-    unitHeight =
-        UnitFrameInterval(_laps[i].InMillisecondsF()) / maxUnitInterval;
-    path.lineTo(width * unitWidth, height * (1.0 - unitHeight));
+  // Prepare a path for the data.
+  // we start at the height of the last point, so it looks like we wrap around
+  SkPath path;
+  const double sampleMarginUnitWidth = (1.0 / kMaxSamples) / 6.0;
+  const double sampleMarginWidth = width * sampleMarginUnitWidth;
+  path.moveTo(x, bottom);
+  path.lineTo(x, y + height * (1.0 - UnitHeight(_laps[0].InMillisecondsF(),
+                                                maxUnitInterval)));
+  double unitX;
+  double unitNextX = 0.0;
+  for (size_t i = 0; i < kMaxSamples; i += 1) {
+    unitX = unitNextX;
+    unitNextX = (static_cast<double>(i + 1) / kMaxSamples);
+    const double sampleY = y + height * (1.0 - UnitHeight(_laps[i].InMillisecondsF(),
+                                                          maxUnitInterval));
+    path.lineTo(x + width * unitX + sampleMarginWidth, sampleY);
+    path.lineTo(x + width * unitNextX - sampleMarginWidth, sampleY);
   }
-
-  path.lineTo(width, height);
-
+  path.lineTo(right, y + height * (1.0 - UnitHeight(_laps[kMaxSamples - 1].InMillisecondsF(),
+                                                    maxUnitInterval)));
+  path.lineTo(right, bottom);
   path.close();
 
+  // Draw the graph.
   paint.setColor(0xAA0000FF);
   canvas.drawPath(path, paint);
 
-  paint.setStrokeWidth(1);
+  // Draw horizontal markers.
+  paint.setStrokeWidth(0); // hairline
   paint.setStyle(SkPaint::Style::kStroke_Style);
-  paint.setColor(0xAAFFFFFF);
+  paint.setColor(0xCC000000);
 
   if (maxInterval > kOneFrameMS) {
     // Paint the horizontal markers
@@ -116,22 +123,22 @@ void Stopwatch::visualize(SkCanvas& canvas, const SkRect& rect) const {
       const double frameHeight =
           height * (1.0 - (UnitFrameInterval((frameIndex + 1) * kOneFrameMS) /
                            maxUnitInterval));
-      canvas.drawLine(0, frameHeight, width, frameHeight, paint);
+      canvas.drawLine(x, y + frameHeight, right, y + frameHeight, paint);
     }
   }
 
-  // Paint the vertical marker
+  // Paint the vertical marker for the last frame.
+  paint.setStyle(SkPaint::Style::kFill_Style);
   if (UnitFrameInterval(lastLap().InMillisecondsF()) > 1.0) {
     // budget exceeded
     paint.setColor(SK_ColorRED);
   } else {
     // within budget
     paint.setColor(SK_ColorGREEN);
   }
-
-  double sampleX = width * (static_cast<double>(_current_sample) / kMaxSamples);
-  paint.setStrokeWidth(3);
-  canvas.drawLine(sampleX, 0, sampleX, height, paint);
+  double sampleX = x + width * (static_cast<double>(_current_sample + 1) / kMaxSamples)
+                     - sampleMarginWidth;
+  canvas.drawRectCoords(sampleX, y, sampleX + sampleMarginWidth * 2.0, bottom, paint);
 }
 
 Stopwatch::~Stopwatch() = default;

flow/instrumentation.h

@@ -13,6 +13,8 @@
 namespace flow {
 namespace instrumentation {
 
+static const double kOneFrameMS = 1e3 / 60.0;
+
 class Stopwatch {
  public:
   class ScopedLap {
@@ -36,6 +38,8 @@ class Stopwatch {
 
   base::TimeDelta currentLap() const { return base::TimeTicks::Now() - _start; }
 
+  base::TimeDelta maxDelta() const;
+
   void visualize(SkCanvas& canvas, const SkRect& rect) const;
 
   void start();
@@ -49,8 +53,6 @@ class Stopwatch {
   std::vector<base::TimeDelta> _laps;
   size_t _current_sample;
 
-  base::TimeDelta maxDelta() const;
-
   DISALLOW_COPY_AND_ASSIGN(Stopwatch);
 };
 

flow/layers/layer.h

@@ -46,6 +46,7 @@ class Layer {
 
   void set_parent(ContainerLayer* parent) { parent_ = parent; }
 
+  // subclasses should assume this will be true by the time Paint() is called
   const bool has_paint_bounds() const { return has_paint_bounds_; }
 
   const SkRect& paint_bounds() const {

flow/layers/performance_overlay_layer.cc

@@ -27,33 +27,36 @@ static void DrawStatisticsText(SkCanvas& canvas,
 
 static void VisualizeStopWatch(SkCanvas& canvas,
                                const instrumentation::Stopwatch& stopwatch,
+                               SkScalar x,
+                               SkScalar y,
                                SkScalar width,
+                               SkScalar height,
                                bool show_graph,
                                bool show_labels,
                                std::string label_prefix) {
-  const int x = 8;
-  const int y = 70;
-  const int height = 80;
+  const int labelX = 8; // distance from x
+  const int labelY = -10; // distance from y+height
 
   if (show_graph) {
-    SkRect visualizationRect = SkRect::MakeWH(width, height);
+    SkRect visualizationRect = SkRect::MakeXYWH(x, y, width, height);
     stopwatch.visualize(canvas, visualizationRect);
   }
 
   if (show_labels) {
-    double msPerFrame = stopwatch.lastLap().InMillisecondsF();
-    double fps = 1e3 / msPerFrame;
+    double msPerFrame = stopwatch.maxDelta().InMillisecondsF();
+    double fps;
+    if (msPerFrame < instrumentation::kOneFrameMS) {
+      fps = 1e3 / instrumentation::kOneFrameMS; 
+    } else {
+      fps = 1e3 / msPerFrame;
+    }
 
     std::stringstream stream;
     stream.setf(std::ios::fixed | std::ios::showpoint);
-    stream << std::setprecision(2);
-    stream << label_prefix << " " << fps << " FPS | " << msPerFrame
-           << "ms/frame";
-    DrawStatisticsText(canvas, stream.str(), x, y);
-  }
-
-  if (show_labels || show_graph) {
-    canvas.translate(0, height);
+    stream << std::setprecision(1);
+    stream << label_prefix << "  " << fps        << " fps  "
+                                   << msPerFrame << "ms/frame";
+    DrawStatisticsText(canvas, stream.str(), x + labelX, y + height + labelY);
   }
 }
 
@@ -62,15 +65,20 @@ void PerformanceOverlayLayer::Paint(PaintContext::ScopedFrame& frame) {
     return;
   }
 
-  SkScalar width = has_paint_bounds() ? paint_bounds().width() : 0;
+  SkScalar x = paint_bounds().x();
+  SkScalar y = paint_bounds().y();
+  SkScalar width = paint_bounds().width();
+  SkScalar height = paint_bounds().height() / 2;
   SkAutoCanvasRestore save(&frame.canvas(), true);
 
-  VisualizeStopWatch(frame.canvas(), frame.context().frame_time(), width,
+  VisualizeStopWatch(frame.canvas(), frame.context().frame_time(),
+                     x, y, width, height,
                      options_ & kVisualizeRasterizerStatistics,
                      options_ & kDisplayRasterizerStatistics,
                      "Rasterizer");
 
-  VisualizeStopWatch(frame.canvas(), frame.context().engine_time(), width,
+  VisualizeStopWatch(frame.canvas(), frame.context().engine_time(),
+                     x, y + height, width, height,
                      options_ & kVisualizeEngineStatistics,
                      options_ & kDisplayEngineStatistics,
                      "Engine");

sky/engine/core/dart/compositing.dart

@@ -104,10 +104,10 @@ class SceneBuilder extends NativeFieldWrapperClass2 {
   /// controls where the statistics are displayed.
   ///
   /// enabledOptions is a bit field with the following bits defined:
-  /// * 0x01: displayRasterizerStatistics - show GPU thread frame time
-  /// * 0x02: visualizeRasterizerStatistics - graph GPU thread frame times
-  /// * 0x04: displayEngineStatistics - show UI thread frame time
-  /// * 0x08: visualizeEngineStatistics - graph UI thread frame times
+  ///  - 0x01: displayRasterizerStatistics - show GPU thread frame time
+  ///  - 0x02: visualizeRasterizerStatistics - graph GPU thread frame times
+  ///  - 0x04: displayEngineStatistics - show UI thread frame time
+  ///  - 0x08: visualizeEngineStatistics - graph UI thread frame times
   /// Set enabledOptions to 0x0F to enable all the currently defined features.
   ///
   /// The "UI thread" is the thread that includes all the execution of