Add FrameRate and improve performance (#93)

- Run the animation at the exported frame rate
- Wrap the animation in a RepaintBoundary
- Don't paint during "static" periods

CHANGELOG.md

@@ -1,3 +1,17 @@
+## [0.6.0]
+- Runs the animation at the frame rate specified in the json file (ie. An animation encoded with a 20 FPS will only
+  be paint 20 times per seconds even though the AnimationController will invalidate the widget 60 times per seconds).  
+  A new property `frameRate` allows to opt-out this behavior and have the widget to repaint at the device frame rate 
+   (`FrameRate.max`).
+- Automatically add a `RepaintBoundary` around the widget. Since `Lottie` animations are generally complex to paint, a
+   `RepaintBoundary` will separate the animation with the rest of the app and improve performance. A new property `addRepaintBoundary`
+   allows to opt-out this behavior.
+- Fix a bug where we would call `markNeedPaint` when the animation was not changing. This removes unnecessary paints in
+  animations with static periods.
+
+## [0.5.1]
+- Remove direct dependencies on dart:io to support Flutter Web
+
 ## [0.5.0]
 - Support loading animation from network in a web app
 - Fix a couple of bugs with the web dev compiler

README.template.md

@@ -17,7 +17,7 @@ This example shows how to display a Lottie animation in the simplest way.
 The `Lottie` widget will load the json file and run the animation indefinitely.
 
 ```dart
-import 'example/lib/examples/main.dart';
+import 'example/lib/main.dart';
 ```
 
 ### Specify a custom `AnimationController`

example/lib/examples/main.dart

@@ -1,27 +0,0 @@
-import 'package:flutter/material.dart';
-import 'package:lottie/lottie.dart';
-
-void main() => runApp(MyApp());
-
-class MyApp extends StatelessWidget {
-  @override
-  Widget build(BuildContext context) {
-    return MaterialApp(
-      home: Scaffold(
-        body: ListView(
-          children: [
-            // Load a Lottie file from your assets
-            Lottie.asset('assets/LottieLogo1.json'),
-
-            // Load a Lottie file from a remote url
-            Lottie.network(
-                'https://raw.githubusercontent.com/xvrh/lottie-flutter/master/example/assets/Mobilo/A.json'),
-
-            // Load an animation and its images from a zip file
-            Lottie.asset('assets/lottiefiles/angel.zip'),
-          ],
-        ),
-      ),
-    );
-  }
-}

example/lib/main.dart

@@ -1,157 +1,24 @@
-import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:logging/logging.dart';
 import 'package:lottie/lottie.dart';
-import 'src/all_files.g.dart';
 
-void main() {
-  Logger.root
-    ..level = Level.ALL
-    ..onRecord.listen(print);
-  Lottie.traceEnabled = true;
-  runApp(App());
-}
+void main() => runApp(MyApp());
 
-class App extends StatelessWidget {
+class MyApp extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
-      //showPerformanceOverlay: true,
       home: Scaffold(
-        appBar: AppBar(
-          title: Text('Lottie Flutter'),
-        ),
-        body: GridView.builder(
-          itemCount: files.length,
-          gridDelegate:
-              SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 4),
-          itemBuilder: (context, index) {
-            var assetName = files[index];
-            return GestureDetector(
-              child: _Item(
-                child: Lottie.asset(
-                  assetName,
-                  frameBuilder: (context, child, composition) {
-                    return AnimatedOpacity(
-                      child: child,
-                      opacity: composition == null ? 0 : 1,
-                      duration: const Duration(seconds: 1),
-                      curve: Curves.easeOut,
-                    );
-                  },
-                ),
-              ),
-              onTap: () {
-                Navigator.of(context).push(MaterialPageRoute<void>(
-                    builder: (context) => Detail(assetName)));
-              },
-            );
-          },
-        ),
-      ),
-    );
-  }
-}
-
-class _Item extends StatelessWidget {
-  final Widget child;
-
-  const _Item({Key key, this.child}) : super(key: key);
-
-  @override
-  Widget build(BuildContext context) {
-    return Padding(
-      padding: const EdgeInsets.all(8.0),
-      child: Container(
-        decoration: BoxDecoration(
-            color: Colors.white,
-            borderRadius: BorderRadius.all(Radius.circular(10)),
-            boxShadow: [
-              BoxShadow(
-                  color: Colors.black.withOpacity(0.1),
-                  offset: Offset(2, 2),
-                  blurRadius: 5)
-            ]),
-        child: child,
-      ),
-    );
-  }
-}
-
-class Detail extends StatefulWidget {
-  final String assetName;
-
-  const Detail(this.assetName, {Key key}) : super(key: key);
-
-  @override
-  _DetailState createState() => _DetailState();
-}
-
-class _DetailState extends State<Detail> with TickerProviderStateMixin {
-  AnimationController _controller;
-
-  @override
-  void initState() {
-    super.initState();
-
-    _controller = AnimationController(vsync: this);
-  }
-
-  @override
-  void dispose() {
-    _controller.dispose();
-
-    super.dispose();
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return Scaffold(
-      appBar: AppBar(
-        title: Text('${widget.assetName}'),
-      ),
-      body: SingleChildScrollView(
-        child: Column(
+        body: ListView(
           children: [
-            Center(
-              child: Lottie.asset(
-                widget.assetName,
-                controller: _controller,
-                onLoaded: (composition) {
-                  _controller.duration = composition.duration;
-                  _controller.repeat();
-                },
-              ),
-            ),
-            AnimatedBuilder(
-              animation: _controller,
-              builder: (context, _) => Row(
-                children: <Widget>[
-                  Expanded(
-                    child: Slider(
-                      value: _controller.value,
-                      onChanged: (newValue) {
-                        _controller.value = newValue;
-                      },
-                    ),
-                  ),
-                  IconButton(
-                    icon: Icon(_controller.isAnimating
-                        ? Icons.stop
-                        : Icons.play_arrow),
-                    onPressed: () {
-                      setState(() {
-                        if (_controller.isAnimating) {
-                          _controller.stop();
-                        } else {
-                          _controller.repeat();
-                        }
-                      });
-                    },
-                  ),
-                ],
-              ),
-            ),
+            // Load a Lottie file from your assets
+            Lottie.asset('assets/LottieLogo1.json'),
+
+            // Load a Lottie file from a remote url
+            Lottie.network(
+                'https://raw.githubusercontent.com/xvrh/lottie-flutter/master/example/assets/Mobilo/A.json'),
+
+            // Load an animation and its images from a zip file
+            Lottie.asset('assets/lottiefiles/angel.zip'),
           ],
         ),
       ),

example/lib/main_app.dart

@@ -0,0 +1,160 @@
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:logging/logging.dart';
+import 'package:lottie/lottie.dart';
+import 'src/all_files.g.dart';
+
+void main() {
+  Logger.root
+    ..level = Level.ALL
+    ..onRecord.listen(print);
+  Lottie.traceEnabled = true;
+  runApp(App());
+}
+
+class App extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      //showPerformanceOverlay: true,
+      home: Scaffold(
+        appBar: AppBar(
+          title: Text('Lottie Flutter'),
+        ),
+        body: GridView.builder(
+          itemCount: files.length,
+          gridDelegate:
+              SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 4),
+          itemBuilder: (context, index) {
+            var assetName = files[index];
+            return GestureDetector(
+              child: _Item(
+                child: Lottie.asset(
+                  assetName,
+                  frameBuilder: (context, child, composition) {
+                    return AnimatedOpacity(
+                      child: child,
+                      opacity: composition == null ? 0 : 1,
+                      duration: const Duration(seconds: 1),
+                      curve: Curves.easeOut,
+                    );
+                  },
+                ),
+              ),
+              onTap: () {
+                Navigator.of(context).push(MaterialPageRoute<void>(
+                    builder: (context) => Detail(assetName)));
+              },
+            );
+          },
+        ),
+      ),
+    );
+  }
+}
+
+class _Item extends StatelessWidget {
+  final Widget child;
+
+  const _Item({Key key, this.child}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Padding(
+      padding: const EdgeInsets.all(8.0),
+      child: Container(
+        decoration: BoxDecoration(
+            color: Colors.white,
+            borderRadius: BorderRadius.all(Radius.circular(10)),
+            boxShadow: [
+              BoxShadow(
+                  color: Colors.black.withOpacity(0.1),
+                  offset: Offset(2, 2),
+                  blurRadius: 5)
+            ]),
+        child: child,
+      ),
+    );
+  }
+}
+
+class Detail extends StatefulWidget {
+  final String assetName;
+
+  const Detail(this.assetName, {Key key}) : super(key: key);
+
+  @override
+  _DetailState createState() => _DetailState();
+}
+
+class _DetailState extends State<Detail> with TickerProviderStateMixin {
+  AnimationController _controller;
+
+  @override
+  void initState() {
+    super.initState();
+
+    _controller = AnimationController(vsync: this);
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('${widget.assetName}'),
+      ),
+      body: SingleChildScrollView(
+        child: Column(
+          children: [
+            Center(
+              child: Lottie.asset(
+                widget.assetName,
+                controller: _controller,
+                onLoaded: (composition) {
+                  _controller.duration = composition.duration;
+                  _controller.repeat();
+                },
+              ),
+            ),
+            AnimatedBuilder(
+              animation: _controller,
+              builder: (context, _) => Row(
+                children: <Widget>[
+                  Expanded(
+                    child: Slider(
+                      value: _controller.value,
+                      onChanged: (newValue) {
+                        _controller.value = newValue;
+                      },
+                    ),
+                  ),
+                  IconButton(
+                    icon: Icon(_controller.isAnimating
+                        ? Icons.stop
+                        : Icons.play_arrow),
+                    onPressed: () {
+                      setState(() {
+                        if (_controller.isAnimating) {
+                          _controller.stop();
+                        } else {
+                          _controller.repeat();
+                        }
+                      });
+                    },
+                  ),
+                ],
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}

example/macos/Podfile.lock

@@ -5,13 +5,13 @@ PODS:
     - FlutterMacOS
 
 DEPENDENCIES:
-  - FlutterMacOS (from `Flutter/ephemeral/.symlinks/flutter/darwin-x64`)
+  - FlutterMacOS (from `Flutter/ephemeral/.symlinks/flutter/darwin-x64-profile`)
   - path_provider (from `Flutter/ephemeral/.symlinks/plugins/path_provider/macos`)
   - path_provider_macos (from `Flutter/ephemeral/.symlinks/plugins/path_provider_macos/macos`)
 
 EXTERNAL SOURCES:
   FlutterMacOS:
-    :path: Flutter/ephemeral/.symlinks/flutter/darwin-x64
+    :path: Flutter/ephemeral/.symlinks/flutter/darwin-x64-profile
   path_provider:
     :path: Flutter/ephemeral/.symlinks/plugins/path_provider/macos
   path_provider_macos:

example/pubspec.lock

@@ -21,7 +21,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.1"
+    version: "2.4.2"
   boolean_selector:
     dependency: transitive
     description:
@@ -35,7 +35,7 @@ packages:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.0"
+    version: "1.1.0-nullsafety"
   charcode:
     dependency: transitive
     description:
@@ -56,7 +56,7 @@ packages:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.12"
+    version: "1.15.0-nullsafety"
   convert:
     dependency: transitive
     description:
@@ -143,21 +143,21 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "0.4.1"
+    version: "0.6.0"
   matcher:
     dependency: transitive
     description:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.6"
+    version: "0.12.8"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.8"
+    version: "1.3.0-nullsafety"
   path:
     dependency: transitive
     description:
@@ -199,7 +199,7 @@ packages:
       name: pedantic
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.0"
+    version: "1.9.2"
   platform:
     dependency: transitive
     description:
@@ -239,7 +239,7 @@ packages:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.3"
+    version: "1.9.5"
   stream_channel:
     dependency: transitive
     description:
@@ -267,21 +267,21 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.16"
+    version: "0.2.17"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.6"
+    version: "1.3.0-nullsafety"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.8"
+    version: "2.1.0-nullsafety"
   xdg_directories:
     dependency: transitive
     description:
@@ -290,5 +290,5 @@ packages:
     source: hosted
     version: "0.1.0"
 sdks:
-  dart: ">=2.7.0 <3.0.0"
+  dart: ">=2.9.0-18.0 <2.9.0"
   flutter: ">=1.12.13+hotfix.5 <2.0.0"

example/test/dynamic_properties_test.dart

@@ -33,6 +33,7 @@ void main() {
           composition: composition,
           controller: animation,
           delegates: LottieDelegates(values: [delegate]),
+          addRepaintBoundary: false,
         ),
       );
       await tester.pump();
@@ -45,6 +46,7 @@ void main() {
             composition: composition,
             controller: animation,
             delegates: LottieDelegates(values: []),
+            addRepaintBoundary: false,
           ),
         );
         await tester.pump();

example/test/utils.dart

@@ -42,7 +42,7 @@ class _CustomerPainter extends CustomPainter {
           thumbSize;
 
       drawable
-        ..setProgress(progress)
+        ..setProgress(progress, frameRate: FrameRate.max)
         ..draw(canvas, rect);
 
       ++index;

example/test/widget_test.dart

@@ -1,5 +1,5 @@
 import 'package:flutter_test/flutter_test.dart';
-import 'package:lottie_example/main.dart';
+import 'package:lottie_example/main_app.dart';
 
 void main() {
   testWidgets('Main sample', (tester) async {

lib/lottie.dart

@@ -1,4 +1,5 @@
 export 'src/composition.dart' show LottieComposition;
+export 'src/frame_rate.dart' show FrameRate;
 export 'src/lottie.dart' show Lottie;
 export 'src/lottie_builder.dart' show LottieBuilder;
 export 'src/lottie_delegates.dart' show LottieDelegates;

lib/src/composition.dart

@@ -3,6 +3,7 @@ import 'dart:typed_data';
 import 'package:archive/archive.dart';
 import 'package:flutter/widgets.dart';
 import 'package:path/path.dart' as p;
+import 'frame_rate.dart';
 import 'logger.dart';
 import 'lottie_image_asset.dart';
 import 'model/font.dart';
@@ -133,9 +134,11 @@ class LottieComposition {
   Rectangle<int> get bounds => _bounds;
 
   Duration get duration {
-    return Duration(milliseconds: (durationFrames / _frameRate * 1000).round());
+    return Duration(milliseconds: (seconds * 1000).round());
   }
 
+  double get seconds => durationFrames / _frameRate;
+
   double get startFrame => _startFrame;
 
   double get endFrame => _endFrame;
@@ -176,6 +179,24 @@ class LottieComposition {
     return _endFrame - _startFrame;
   }
 
+  /// Returns a "rounded" progress value according to the frameRate
+  double roundProgress(double progress, {@required FrameRate frameRate}) {
+    num fps;
+    if (frameRate == FrameRate.max) {
+      return progress;
+    } else if (frameRate == FrameRate.composition) {
+      fps = this.frameRate;
+    }
+    fps ??= frameRate.framesPerSecond;
+
+    var totalFrameCount = seconds * fps;
+    var frameIndex = (totalFrameCount * progress).toInt();
+    var roundedProgress = frameIndex / totalFrameCount;
+    assert(roundedProgress >= 0 && roundedProgress <= 1,
+        'Progress is $roundedProgress');
+    return roundedProgress;
+  }
+
   @override
   String toString() {
     final sb = StringBuffer('LottieComposition:\n');

lib/src/frame_rate.dart

@@ -0,0 +1,9 @@
+class FrameRate {
+  static final max = FrameRate._special(0);
+  static final composition = FrameRate._special(-1);
+
+  final double framesPerSecond;
+
+  FrameRate(this.framesPerSecond) : assert(framesPerSecond > 0);
+  FrameRate._special(this.framesPerSecond);
+}

lib/src/lottie.dart

@@ -1,8 +1,8 @@
-import 'dart:io';
 import 'dart:typed_data';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 import '../lottie.dart';
+import 'frame_rate.dart';
 import 'l.dart';
 import 'lottie_builder.dart';
 import 'options.dart';
@@ -23,36 +23,44 @@ class Lottie extends StatefulWidget {
     this.alignment,
     this.fit,
     bool animate,
+    this.frameRate,
     bool repeat,
     bool reverse,
     this.delegates,
     this.options,
+    bool addRepaintBoundary,
   })  : animate = animate ?? true,
         reverse = reverse ?? false,
         repeat = repeat ?? true,
+        addRepaintBoundary = addRepaintBoundary ?? true,
         super(key: key);
 
   /// Creates a widget that displays an [LottieComposition] obtained from an [AssetBundle].
-  static LottieBuilder asset(String name,
-          {Animation<double> controller,
-          bool animate,
-          bool repeat,
-          bool reverse,
-          LottieDelegates delegates,
-          LottieOptions options,
-          void Function(LottieComposition) onLoaded,
-          LottieImageProviderFactory imageProviderFactory,
-          Key key,
-          AssetBundle bundle,
-          LottieFrameBuilder frameBuilder,
-          double width,
-          double height,
-          BoxFit fit,
-          Alignment alignment,
-          String package}) =>
+  static LottieBuilder asset(
+    String name, {
+    Animation<double> controller,
+    bool animate,
+    FrameRate frameRate,
+    bool repeat,
+    bool reverse,
+    LottieDelegates delegates,
+    LottieOptions options,
+    void Function(LottieComposition) onLoaded,
+    LottieImageProviderFactory imageProviderFactory,
+    Key key,
+    AssetBundle bundle,
+    LottieFrameBuilder frameBuilder,
+    double width,
+    double height,
+    BoxFit fit,
+    Alignment alignment,
+    String package,
+    bool addRepaintBoundary,
+  }) =>
       LottieBuilder.asset(
         name,
         controller: controller,
+        frameRate: frameRate,
         animate: animate,
         repeat: repeat,
         reverse: reverse,
@@ -68,12 +76,14 @@ class Lottie extends StatefulWidget {
         fit: fit,
         alignment: alignment,
         package: package,
+        addRepaintBoundary: addRepaintBoundary,
       );
 
   /// Creates a widget that displays an [LottieComposition] obtained from a [File].
   static LottieBuilder file(
-    File file, {
+    Object /*io.File|html.File*/ file, {
     Animation<double> controller,
+    FrameRate frameRate,
     bool animate,
     bool repeat,
     bool reverse,
@@ -87,10 +97,12 @@ class Lottie extends StatefulWidget {
     double height,
     BoxFit fit,
     Alignment alignment,
+    bool addRepaintBoundary,
   }) =>
       LottieBuilder.file(
         file,
         controller: controller,
+        frameRate: frameRate,
         animate: animate,
         repeat: repeat,
         reverse: reverse,
@@ -104,12 +116,14 @@ class Lottie extends StatefulWidget {
         height: height,
         fit: fit,
         alignment: alignment,
+        addRepaintBoundary: addRepaintBoundary,
       );
 
   /// Creates a widget that displays an [LottieComposition] obtained from a [Uint8List].
   static LottieBuilder memory(
     Uint8List bytes, {
     Animation<double> controller,
+    FrameRate frameRate,
     bool animate,
     bool repeat,
     bool reverse,
@@ -123,10 +137,12 @@ class Lottie extends StatefulWidget {
     double height,
     BoxFit fit,
     Alignment alignment,
+    bool addRepaintBoundary,
   }) =>
       LottieBuilder.memory(
         bytes,
         controller: controller,
+        frameRate: frameRate,
         animate: animate,
         repeat: repeat,
         reverse: reverse,
@@ -140,12 +156,14 @@ class Lottie extends StatefulWidget {
         height: height,
         fit: fit,
         alignment: alignment,
+        addRepaintBoundary: addRepaintBoundary,
       );
 
   /// Creates a widget that displays an [LottieComposition] obtained from the network.
   static LottieBuilder network(
     String url, {
     Animation<double> controller,
+    FrameRate frameRate,
     bool animate,
     bool repeat,
     bool reverse,
@@ -159,10 +177,12 @@ class Lottie extends StatefulWidget {
     double height,
     BoxFit fit,
     Alignment alignment,
+    bool addRepaintBoundary,
   }) =>
       LottieBuilder.network(
         url,
         controller: controller,
+        frameRate: frameRate,
         animate: animate,
         repeat: repeat,
         reverse: reverse,
@@ -176,6 +196,7 @@ class Lottie extends StatefulWidget {
         height: height,
         fit: fit,
         alignment: alignment,
+        addRepaintBoundary: addRepaintBoundary,
       );
 
   /// The Lottie composition to animate.
@@ -187,6 +208,14 @@ class Lottie extends StatefulWidget {
   /// with the properties [animate], [reverse]
   final Animation<double> controller;
 
+  /// The number of frames per second to render.
+  /// Use `FrameRate.composition` to use the original frame rate of the Lottie composition (default)
+  /// Use `FrameRate.max` to advance the animation progression at every frame.
+  ///
+  /// The advantage of using a low frame rate is to preserve the device battery
+  /// by doing less rendering work.
+  final FrameRate frameRate;
+
   /// If no controller is specified, this value indicate whether or not the
   /// Lottie animation should be played automatically (default to true).
   /// If there is an animation controller specified, this property has no effect.
@@ -250,6 +279,13 @@ class Lottie extends StatefulWidget {
   /// - enableMergePaths: Enable merge path support
   final LottieOptions options;
 
+  /// Indicate to automatically add a `RepaintBoundary` widget around the animation.
+  /// This allows to optimize the app performance by isolating the animation in its
+  /// own `Layer`.
+  ///
+  /// This property is `true` by default.
+  final bool addRepaintBoundary;
+
   static bool get traceEnabled => L.traceEnabled;
   static set traceEnabled(bool enabled) {
     L.traceEnabled = enabled;
@@ -304,18 +340,27 @@ class _LottieState extends State<Lottie> with TickerProviderStateMixin {
 
   @override
   Widget build(BuildContext context) {
-    return AnimatedBuilder(
+    Widget child = AnimatedBuilder(
       animation: _progressAnimation,
-      builder: (context, _) => RawLottie(
-        composition: widget.composition,
-        delegates: widget.delegates,
-        options: widget.options,
-        progress: _progressAnimation.value,
-        width: widget.width,
-        height: widget.height,
-        fit: widget.fit,
-        alignment: widget.alignment,
-      ),
+      builder: (context, _) {
+        return RawLottie(
+          composition: widget.composition,
+          delegates: widget.delegates,
+          options: widget.options,
+          progress: _progressAnimation.value,
+          frameRate: widget.frameRate,
+          width: widget.width,
+          height: widget.height,
+          fit: widget.fit,
+          alignment: widget.alignment,
+        );
+      },
     );
+
+    if (widget.addRepaintBoundary) {
+      child = RepaintBoundary(child: child);
+    }
+
+    return child;
   }
 }

lib/src/lottie_builder.dart

@@ -1,10 +1,10 @@
 import 'dart:async';
-import 'dart:io';
 import 'dart:typed_data';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 import '../lottie.dart';
+import 'frame_rate.dart';
 import 'lottie.dart';
 import 'providers/asset_provider.dart';
 import 'providers/file_provider.dart';
@@ -36,6 +36,7 @@ class LottieBuilder extends StatefulWidget {
     Key key,
     @required this.lottie,
     this.controller,
+    this.frameRate,
     this.animate,
     this.reverse,
     this.repeat,
@@ -47,6 +48,7 @@ class LottieBuilder extends StatefulWidget {
     this.height,
     this.fit,
     this.alignment,
+    this.addRepaintBoundary,
   })  : assert(lottie != null),
         super(key: key);
 
@@ -55,6 +57,7 @@ class LottieBuilder extends StatefulWidget {
     String src, {
     Map<String, String> headers,
     this.controller,
+    this.frameRate,
     this.animate,
     this.reverse,
     this.repeat,
@@ -68,6 +71,7 @@ class LottieBuilder extends StatefulWidget {
     this.height,
     this.fit,
     this.alignment,
+    this.addRepaintBoundary,
   })  : lottie = NetworkLottie(src,
             headers: headers, imageProviderFactory: imageProviderFactory),
         super(key: key);
@@ -83,8 +87,9 @@ class LottieBuilder extends StatefulWidget {
   /// `android.permission.READ_EXTERNAL_STORAGE` permission.
   ///
   LottieBuilder.file(
-    File file, {
+    Object /*io.File|html.File*/ file, {
     this.controller,
+    this.frameRate,
     this.animate,
     this.reverse,
     this.repeat,
@@ -98,6 +103,7 @@ class LottieBuilder extends StatefulWidget {
     this.height,
     this.fit,
     this.alignment,
+    this.addRepaintBoundary,
   })  : lottie = FileLottie(file, imageProviderFactory: imageProviderFactory),
         super(key: key);
 
@@ -105,6 +111,7 @@ class LottieBuilder extends StatefulWidget {
   LottieBuilder.asset(
     String name, {
     this.controller,
+    this.frameRate,
     this.animate,
     this.reverse,
     this.repeat,
@@ -120,6 +127,7 @@ class LottieBuilder extends StatefulWidget {
     this.fit,
     this.alignment,
     String package,
+    this.addRepaintBoundary,
   })  : lottie = AssetLottie(name,
             bundle: bundle,
             package: package,
@@ -130,6 +138,7 @@ class LottieBuilder extends StatefulWidget {
   LottieBuilder.memory(
     Uint8List bytes, {
     this.controller,
+    this.frameRate,
     this.animate,
     this.reverse,
     this.repeat,
@@ -143,6 +152,7 @@ class LottieBuilder extends StatefulWidget {
     this.height,
     this.fit,
     this.alignment,
+    this.addRepaintBoundary,
   })  : lottie =
             MemoryLottie(bytes, imageProviderFactory: imageProviderFactory),
         super(key: key);
@@ -161,6 +171,11 @@ class LottieBuilder extends StatefulWidget {
   /// Lottie animation.
   final Animation<double> controller;
 
+  /// The number of frames per second to render.
+  /// Use `FrameRate.composition` to use the original frame rate of the Lottie composition (default)
+  /// Use `FrameRate.max` to advance the animation progression at every frame.
+  final FrameRate frameRate;
+
   /// If no controller is specified, this value indicate whether or not the
   /// Lottie animation should be played automatically (default to true).
   /// If there is an animation controller specified, this property has no effect.
@@ -321,6 +336,13 @@ class LottieBuilder extends StatefulWidget {
   ///    relative to text direction.
   final AlignmentGeometry alignment;
 
+  /// Indicate to automatically add a `RepaintBoundary` widget around the animation.
+  /// This allows to optimize the app performance by isolating the animation in its
+  /// own `Layer`.
+  ///
+  /// This property is `true` by default.
+  final bool addRepaintBoundary;
+
   @override
   _LottieBuilderState createState() => _LottieBuilderState();
 
@@ -384,6 +406,7 @@ class _LottieBuilderState extends State<LottieBuilder> {
         Widget result = Lottie(
           composition: composition,
           controller: widget.controller,
+          frameRate: widget.frameRate,
           animate: widget.animate,
           reverse: widget.reverse,
           repeat: widget.repeat,
@@ -393,6 +416,7 @@ class _LottieBuilderState extends State<LottieBuilder> {
           height: widget.height,
           fit: widget.fit,
           alignment: widget.alignment,
+          addRepaintBoundary: widget.addRepaintBoundary,
         );
 
         if (widget.frameBuilder != null) {

lib/src/lottie_delegates.dart

@@ -3,7 +3,7 @@ import 'lottie_drawable.dart';
 import 'value_delegate.dart';
 
 // TODO(xha): recognize style Bold, Medium, Regular, SemiBold, etc...
-TextStyle _defaultTextStyleDelegate(LottieFontStyle font) =>
+TextStyle defaultTextStyleDelegate(LottieFontStyle font) =>
     TextStyle(fontFamily: font.fontFamily);
 
 @immutable
@@ -49,7 +49,7 @@ class LottieDelegates {
     this.text,
     TextStyle Function(LottieFontStyle) textStyle,
     this.values,
-  }) : textStyle = textStyle ?? _defaultTextStyleDelegate;
+  }) : textStyle = textStyle;
 
   @override
   bool operator ==(Object other) =>

lib/src/lottie_drawable.dart

@@ -2,6 +2,7 @@ import 'dart:ui' as ui;
 import 'package:flutter/rendering.dart';
 import 'package:vector_math/vector_math_64.dart';
 import 'composition.dart';
+import 'frame_rate.dart';
 import 'lottie_delegates.dart';
 import 'model/key_path.dart';
 import 'model/layer/composition_layer.dart';
@@ -43,26 +44,32 @@ class LottieDrawable {
     _isDirty = true;
   }
 
-  double get progress => _progress;
-  double _progress = 0.0;
-  bool setProgress(double value) {
-    _isDirty = false;
-    _progress = value;
-    _compositionLayer.setProgress(value);
-    return _isDirty;
+  double get progress => _progress ?? 0.0;
+  double _progress;
+  bool setProgress(double value, {FrameRate frameRate}) {
+    frameRate ??= FrameRate.composition;
+    var roundedProgress =
+        composition.roundProgress(value, frameRate: frameRate);
+    if (roundedProgress != _progress) {
+      _isDirty = false;
+      _progress = roundedProgress;
+      _compositionLayer.setProgress(roundedProgress);
+      return _isDirty;
+    } else {
+      return false;
+    }
   }
 
   LottieDelegates get delegates => _delegates;
   set delegates(LottieDelegates delegates) {
-    delegates ??= LottieDelegates();
     if (_delegates != delegates) {
       _delegates = delegates;
-      _updateValueDelegates(delegates.values);
+      _updateValueDelegates(delegates?.values);
     }
   }
 
   bool get useTextGlyphs {
-    return delegates.text == null && composition.characters.isNotEmpty;
+    return delegates?.text == null && composition.characters.isNotEmpty;
   }
 
   ui.Image getImageAsset(String ref) {
@@ -75,8 +82,8 @@ class LottieDrawable {
   }
 
   TextStyle getTextStyle(String font, String style) {
-    return _delegates
-        .textStyle(LottieFontStyle(fontFamily: font, style: style));
+    return (_delegates?.textStyle ?? defaultTextStyleDelegate)(
+        LottieFontStyle(fontFamily: font, style: style));
   }
 
   List<ValueDelegate> _valueDelegates = <ValueDelegate>[];

lib/src/model/layer/text_layer.dart

@@ -232,7 +232,7 @@ class TextLayer extends BaseLayer {
       return;
     }
     var text = documentData.text;
-    var textDelegate = lottieDrawable.delegates.text;
+    var textDelegate = lottieDrawable.delegates?.text;
     if (textDelegate != null) {
       text = textDelegate(text);
     }

lib/src/providers/file_provider.dart

@@ -1,25 +1,24 @@
-import 'dart:io';
 import 'dart:ui' as ui;
-import 'package:flutter/rendering.dart';
 import 'package:path/path.dart' as p;
 import '../composition.dart';
 import '../lottie_image_asset.dart';
 import 'load_image.dart';
 import 'lottie_provider.dart';
+import 'provider_io.dart' if (dart.library.html) 'provider_web.dart' as io;
 
 class FileLottie extends LottieProvider {
   FileLottie(this.file, {LottieImageProviderFactory imageProviderFactory})
       : super(imageProviderFactory: imageProviderFactory);
 
-  final File file;
+  final Object /*io.File|html.File*/ file;
 
   @override
   Future<LottieComposition> load() async {
-    var cacheKey = 'file-${file.path}';
+    var cacheKey = 'file-${io.filePath(file)}';
     return sharedLottieCache.putIfAbsent(cacheKey, () async {
-      var bytes = await file.readAsBytes();
+      var bytes = await io.loadFile(file);
       var composition = await LottieComposition.fromBytes(bytes,
-          name: p.basenameWithoutExtension(file.path));
+          name: p.basenameWithoutExtension(io.filePath(file)));
 
       for (var image in composition.images.values) {
         image.loadedImage ??= await _loadImage(composition, image);
@@ -33,11 +32,7 @@ class FileLottie extends LottieProvider {
       LottieComposition composition, LottieImageAsset lottieImage) {
     var imageProvider = getImageProvider(lottieImage);
 
-    if (imageProvider == null) {
-      var imagePath = p.url.join(
-          p.dirname(file.path), lottieImage.dirName, lottieImage.fileName);
-      imageProvider = FileImage(File(imagePath));
-    }
+    imageProvider ??= io.loadImageForFile(file, lottieImage);
 
     return loadImage(composition, lottieImage, imageProvider);
   }
@@ -52,5 +47,5 @@ class FileLottie extends LottieProvider {
   int get hashCode => file.hashCode;
 
   @override
-  String toString() => '$runtimeType(file: ${file.path})';
+  String toString() => '$runtimeType(file: ${io.filePath(file)})';
 }

lib/src/providers/network_provider.dart

@@ -6,8 +6,7 @@ import '../composition.dart';
 import '../lottie_image_asset.dart';
 import 'load_image.dart';
 import 'lottie_provider.dart';
-import 'network_provider_io.dart'
-    if (dart.library.html) 'network_provider_web.dart' as network;
+import 'provider_io.dart' if (dart.library.html) 'provider_web.dart' as network;
 
 class NetworkLottie extends LottieProvider {
   NetworkLottie(this.url,
@@ -22,7 +21,7 @@ class NetworkLottie extends LottieProvider {
     var cacheKey = 'network-$url';
     return sharedLottieCache.putIfAbsent(cacheKey, () async {
       var resolved = Uri.base.resolve(url);
-      var bytes = await network.load(resolved, headers: headers);
+      var bytes = await network.loadHttp(resolved, headers: headers);
 
       var composition = await LottieComposition.fromBytes(bytes,
           name: p.url.basenameWithoutExtension(url));

lib/src/providers/network_provider_web.dart

@@ -1,16 +0,0 @@
-import 'dart:html';
-import 'dart:typed_data';
-
-Future<Uint8List> load(Uri uri, {Map<String, String> headers}) async {
-  var request = await HttpRequest.request(uri.toString(),
-      requestHeaders: headers, responseType: 'blob');
-
-  var reader = FileReader();
-  reader.readAsArrayBuffer(request.response as Blob);
-  await reader.onLoadEnd.first;
-  if (reader.readyState != FileReader.DONE) {
-    throw Exception('Error while reading $uri');
-  }
-
-  return reader.result as Uint8List;
-}

lib/src/providers/provider_io.dart

@@ -1,10 +1,13 @@
 import 'dart:io';
 import 'dart:typed_data';
 import 'package:flutter/foundation.dart';
+import 'package:flutter/widgets.dart';
+import 'package:path/path.dart' as p;
+import '../lottie_image_asset.dart';
 
 final HttpClient _sharedHttpClient = HttpClient()..autoUncompress = false;
 
-Future<Uint8List> load(Uri uri, {Map<String, String> headers}) async {
+Future<Uint8List> loadHttp(Uri uri, {Map<String, String> headers}) async {
   var request = await _sharedHttpClient.getUrl(uri);
   headers?.forEach((String name, String value) {
     request.headers.add(name, value);
@@ -21,3 +24,19 @@ Future<Uint8List> load(Uri uri, {Map<String, String> headers}) async {
 
   return bytes;
 }
+
+Future<Uint8List> loadFile(Object file) {
+  return (file as File).readAsBytes();
+}
+
+String filePath(Object file) {
+  return (file as File).path;
+}
+
+ImageProvider loadImageForFile(Object file, LottieImageAsset lottieImage) {
+  var fileIo = file as File;
+
+  var imagePath = p.url
+      .join(p.dirname(fileIo.path), lottieImage.dirName, lottieImage.fileName);
+  return FileImage(File(imagePath));
+}

lib/src/providers/provider_web.dart

@@ -0,0 +1,35 @@
+import 'dart:html';
+import 'dart:typed_data';
+import 'package:flutter/rendering.dart';
+import '../lottie_image_asset.dart';
+
+Future<Uint8List> loadHttp(Uri uri, {Map<String, String> headers}) async {
+  var request = await HttpRequest.request(uri.toString(),
+      requestHeaders: headers, responseType: 'blob');
+
+  return _loadBlob(request.response as Blob);
+}
+
+Future<Uint8List> loadFile(Object file) {
+  return _loadBlob(file as File);
+}
+
+Future<Uint8List> _loadBlob(Blob file) async {
+  var reader = FileReader();
+  reader.readAsArrayBuffer(file);
+
+  await reader.onLoadEnd.first;
+  if (reader.readyState != FileReader.DONE) {
+    throw Exception('Error while reading blob');
+  }
+
+  return reader.result as Uint8List;
+}
+
+String filePath(Object file) {
+  return (file as File).relativePath;
+}
+
+ImageProvider loadImageForFile(Object file, LottieImageAsset lottieImage) {
+  return null;
+}

lib/src/raw_lottie.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import '../lottie.dart';
+import 'frame_rate.dart';
 import 'lottie_drawable.dart';
 import 'render_lottie.dart';
 
@@ -15,6 +16,7 @@ class RawLottie extends LeafRenderObjectWidget {
     this.delegates,
     this.options,
     double progress,
+    this.frameRate,
     this.width,
     this.height,
     this.fit,
@@ -34,6 +36,11 @@ class RawLottie extends LeafRenderObjectWidget {
   /// The progress of the Lottie animation (between 0.0 and 1.0).
   final double progress;
 
+  /// The number of frames per second to render.
+  /// Use `FrameRate.composition` to use the original frame rate of the Lottie composition (default)
+  /// Use `FrameRate.max` to advance the animation progression at every frame.
+  final FrameRate frameRate;
+
   /// If non-null, require the Lottie composition to have this width.
   ///
   /// If null, the composition will pick a size that best preserves its intrinsic
@@ -76,6 +83,7 @@ class RawLottie extends LeafRenderObjectWidget {
       delegates: delegates,
       enableMergePaths: options?.enableMergePaths,
       progress: progress,
+      frameRate: frameRate,
       width: width,
       height: height,
       fit: fit,
@@ -88,6 +96,7 @@ class RawLottie extends LeafRenderObjectWidget {
     renderObject
       ..setComposition(composition,
           progress: progress,
+          frameRate: frameRate,
           delegates: delegates,
           enableMergePaths: options?.enableMergePaths)
       ..width = width

lib/src/render_lottie.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/rendering.dart';
 import 'package:meta/meta.dart';
 import '../lottie.dart';
+import 'frame_rate.dart';
 import 'lottie_drawable.dart';
 
 /// A Lottie animation in the render tree.
@@ -9,10 +10,11 @@ import 'lottie_drawable.dart';
 /// constraints and preserves the composition's intrinsic aspect ratio.
 class RenderLottie extends RenderBox {
   RenderLottie({
-    LottieComposition composition,
+    @required LottieComposition composition,
     LottieDelegates delegates,
     bool enableMergePaths,
     double progress = 0.0,
+    FrameRate frameRate,
     double width,
     double height,
     BoxFit fit,
@@ -21,7 +23,7 @@ class RenderLottie extends RenderBox {
         assert(progress != null && progress >= 0.0 && progress <= 1.0),
         _drawable = composition != null
             ? (LottieDrawable(composition, enableMergePaths: enableMergePaths)
-              ..setProgress(progress)
+              ..setProgress(progress, frameRate: frameRate)
               ..delegates = delegates)
             : null,
         _width = width,
@@ -34,6 +36,7 @@ class RenderLottie extends RenderBox {
   LottieDrawable _drawable;
   void setComposition(LottieComposition composition,
       {@required double progress,
+      @required FrameRate frameRate,
       @required LottieDelegates delegates,
       bool enableMergePaths}) {
     enableMergePaths ??= false;
@@ -41,9 +44,11 @@ class RenderLottie extends RenderBox {
     var needsLayout = false;
     var needsPaint = false;
     if (composition == null) {
-      _drawable = null;
-      needsPaint = true;
-      needsLayout = true;
+      if (_drawable != null) {
+        _drawable = null;
+        needsPaint = true;
+        needsLayout = true;
+      }
     } else {
       if (_drawable == null ||
           _drawable.composition != composition ||
@@ -54,7 +59,7 @@ class RenderLottie extends RenderBox {
         needsPaint = true;
       }
 
-      needsPaint |= _drawable.setProgress(progress);
+      needsPaint |= _drawable.setProgress(progress, frameRate: frameRate);
 
       if (_drawable.delegates != delegates) {
         _drawable.delegates = delegates;

pubspec.lock

@@ -7,14 +7,14 @@ packages:
       name: _fe_analyzer_shared
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "5.0.0"
+    version: "6.0.0"
   analyzer:
     dependency: "direct dev"
     description:
       name: analyzer
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.39.12"
+    version: "0.39.15"
   archive:
     dependency: "direct main"
     description:
@@ -35,7 +35,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.1"
+    version: "2.4.2"
   boolean_selector:
     dependency: transitive
     description:
@@ -49,7 +49,7 @@ packages:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.0"
+    version: "1.1.0-nullsafety"
   charcode:
     dependency: "direct main"
     description:
@@ -57,6 +57,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.1.3"
+  cli_util:
+    dependency: transitive
+    description:
+      name: cli_util
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.1.4"
   clock:
     dependency: transitive
     description:
@@ -70,7 +77,7 @@ packages:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.12"
+    version: "1.15.0-nullsafety"
   convert:
     dependency: transitive
     description:
@@ -91,7 +98,7 @@ packages:
       name: csslib
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.16.1"
+    version: "0.16.2"
   dart_style:
     dependency: "direct dev"
     description:
@@ -150,14 +157,14 @@ packages:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.6"
+    version: "0.12.8"
   meta:
     dependency: "direct main"
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.8"
+    version: "1.3.0-nullsafety"
   mockito:
     dependency: "direct dev"
     description:
@@ -199,7 +206,7 @@ packages:
       name: pedantic
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.0"
+    version: "1.9.2"
   pub_semver:
     dependency: transitive
     description:
@@ -225,7 +232,7 @@ packages:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.3"
+    version: "1.9.5"
   stream_channel:
     dependency: transitive
     description:
@@ -253,21 +260,21 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.16"
+    version: "0.2.17"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.6"
+    version: "1.3.0-nullsafety"
   vector_math:
     dependency: "direct main"
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.8"
+    version: "2.1.0-nullsafety"
   watcher:
     dependency: transitive
     description:
@@ -283,4 +290,4 @@ packages:
     source: hosted
     version: "2.2.1"
 sdks:
-  dart: ">=2.7.0 <3.0.0"
+  dart: ">=2.9.0-18.0 <2.9.0"

pubspec.yaml

@@ -1,6 +1,6 @@
 name: lottie
 description: Render After Effects animations natively on Flutter. This package is a pure Dart implementation of a Lottie player.
-version: 0.5.0
+version: 0.6.0
 homepage: https://github.com/xvrh/lottie-flutter
 
 environment:

test/frame_rate_test.dart

@@ -0,0 +1,14 @@
+import 'dart:io';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:lottie/lottie.dart';
+
+void main() {
+  test('Frame rate round', () async {
+    var composition = await LottieComposition.fromBytes(
+        File('example/assets/LottieLogo1.json').readAsBytesSync());
+    expect(composition.roundProgress(0, frameRate: FrameRate.composition), 0);
+    expect(
+        composition.roundProgress(0.0001, frameRate: FrameRate.composition), 0);
+    expect(composition.roundProgress(0.0001, frameRate: FrameRate.max), 0.0001);
+  });
+}