TF-495 Show FPS when load more emails

core/lib/core.dart

@@ -27,6 +27,7 @@ export 'presentation/utils/html_transformer/dom/add_tooltip_link_transformers.da
 export 'data/utils/device_manager.dart';
 export 'utils/app_logger.dart';
 export 'utils/benchmark.dart';
+export 'utils/fps_manager.dart';
 
 // Views
 export 'presentation/views/text/slogan_builder.dart';

core/lib/utils/fps_manager.dart

@@ -0,0 +1,128 @@
+import 'dart:collection';
+import 'dart:ui';
+
+import 'package:flutter/scheduler.dart';
+
+/// FpsManager callback.
+typedef FpsCallback = void Function(FpsInfo fpsInfo);
+
+class FpsManager {
+
+  FpsManager._();
+
+  factory FpsManager() => _instance ??= FpsManager._();
+
+  static FpsManager? _instance;
+
+  /// Threshold time consuming per frame
+  /// 1000/60hz ≈ 16.6ms  1000/120hz ≈ 8.3ms
+  Duration _thresholdPerFrame = Duration(microseconds: Duration.microsecondsPerSecond ~/ 60);
+
+  /// Refresh rate, default 60
+  double _refreshRate = 60;
+
+  /// Set refresh rate
+  set refreshRate(double rate) {
+    if (rate != _refreshRate && rate >= 60) {
+      _refreshRate = rate;
+      _thresholdPerFrame = Duration(microseconds: Duration.microsecondsPerSecond ~/ _refreshRate);
+    }
+  }
+
+  bool _started = false;
+  List<FpsCallback> _fpsCallbacks = [];
+
+  /// Temporarily save 120 frames
+  static const int _queue_capacity = 120;
+  final ListQueue framesQueue = ListQueue<FrameTiming>(_queue_capacity);
+
+  void addFpsCallback(FpsCallback callback) {
+    _fpsCallbacks.add(callback);
+  }
+
+  void removeFpsCallback(FpsCallback callback) {
+    assert(_fpsCallbacks.contains(callback));
+    _fpsCallbacks.remove(callback);
+  }
+
+  void start() async {
+    if (!_started) {
+      SchedulerBinding.instance?.addTimingsCallback(_onTimingsCallback);
+      _started = true;
+    }
+  }
+
+  void stop() {
+    if (_started) {
+      SchedulerBinding.instance?.removeTimingsCallback(_onTimingsCallback);
+      _started = false;
+    }
+  }
+
+  _onTimingsCallback(List<FrameTiming> timings) async {
+    if (_fpsCallbacks.isNotEmpty) {
+      for (FrameTiming timing in timings) {
+        framesQueue.addFirst(timing);
+      }
+      while (framesQueue.length > _queue_capacity) {
+        framesQueue.removeLast();
+      }
+
+      List<FrameTiming> drawFrames = [];
+      for (FrameTiming timing in framesQueue) {
+        if (drawFrames.isEmpty) {
+          drawFrames.add(timing);
+        } else {
+          int lastStart =
+          drawFrames.last.timestampInMicroseconds(FramePhase.vsyncStart);
+          int interval = lastStart -
+              timing.timestampInMicroseconds(FramePhase.rasterFinish);
+          if (interval > (_thresholdPerFrame.inMicroseconds * 2)) {
+            // maybe in different set
+            break;
+          }
+          drawFrames.add(timing);
+        }
+      }
+      framesQueue.clear();
+
+      // compute total frames count.
+      int totalCount = drawFrames.map((frame) {
+        // If droppedCount > 0,
+        int droppedCount = frame.totalSpan.inMicroseconds ~/ _thresholdPerFrame.inMicroseconds;
+        return droppedCount + 1;
+      }).fold(0, (a, b) => a + b);
+
+      int drawFramesCount = drawFrames.length;
+      int droppedCount = totalCount - drawFramesCount;
+      double fps = drawFramesCount / totalCount * _refreshRate;
+      FpsInfo fpsInfo = FpsInfo(fps, totalCount, droppedCount, drawFramesCount);
+      _fpsCallbacks.forEach((callBack) {
+        callBack(fpsInfo);
+      });
+    }
+  }
+}
+
+class FpsInfo {
+  final double fps;
+  final int totalFramesCount;
+  final int droppedFramesCount;
+  final int drawFramesCount;
+
+  FpsInfo(
+    this.fps,
+    this.totalFramesCount,
+    this.droppedFramesCount,
+    this.drawFramesCount
+  );
+
+  @override
+  String toString() {
+    return 'FpsInfo{'
+        'fps: $fps, '
+        'totalFramesCount: $totalFramesCount, '
+        'droppedFramesCount: $droppedFramesCount, '
+        'drawFramesCount: $drawFramesCount}';
+  }
+}