SimpleAnimation exposes mix

lib/src/controllers/simple_controller.dart

@@ -7,9 +7,16 @@ import 'package:rive/src/runtime_artboard.dart';
 /// by an artist. All playback parameters (looping, speed, keyframes) are artist
 /// defined in the Rive editor.
 class SimpleAnimation extends RiveAnimationController<RuntimeArtboard> {
+  SimpleAnimation(this.animationName, {double mix})
+      : _mix = mix?.clamp(0, 1)?.toDouble() ?? 1.0;
+
   LinearAnimationInstance _instance;
   final String animationName;
-  SimpleAnimation(this.animationName);
+
+  // Controls the level of mix for the animation, clamped between 0 and 1
+  double _mix;
+  double get mix => _mix;
+  set mix(double value) => _mix = value?.clamp(0, 1)?.toDouble() ?? 1;
 
   LinearAnimationInstance get instance => _instance;
 
@@ -29,7 +36,7 @@ class SimpleAnimation extends RiveAnimationController<RuntimeArtboard> {
 
   @override
   void apply(RuntimeArtboard artboard, double elapsedSeconds) {
-    _instance.animation.apply(_instance.time, coreContext: artboard);
+    _instance.animation.apply(_instance.time, coreContext: artboard, mix: mix);
     if (!_instance.advance(elapsedSeconds)) {
       isActive = false;
     }

test/simple_animation_test.dart

@@ -0,0 +1,43 @@
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:rive/rive.dart';
+
+void main() {
+  ByteData riveData;
+
+  void loadTestAssets() {
+    riveData = ByteData.sublistView(
+      File('assets/animations_0_6_2.riv').readAsBytesSync(),
+    );
+  }
+
+  setUp(loadTestAssets);
+
+  test('SimpleAnimation exposes mix', () {
+    // Load a Rive file
+    final riveFile = RiveFile();
+    expect(riveFile.import(riveData), true);
+    expect(riveFile.mainArtboard.name, 'My Artboard');
+
+    final firstController =
+        SimpleAnimation(riveFile.mainArtboard.animations.first.name);
+    expect(firstController.animationName, 'First');
+    expect(firstController.mix, 1.0);
+
+    firstController.mix = 0.5;
+    expect(firstController.mix, 0.5);
+
+    firstController.mix = 2.5;
+    expect(firstController.mix, 1.0);
+
+    firstController.mix = -1;
+    expect(firstController.mix, 0.0);
+
+    final secondController =
+        SimpleAnimation(riveFile.mainArtboard.animations.last.name, mix: 0.8);
+    expect(secondController.animationName, 'Second');
+    expect(secondController.mix, 0.8);
+  });
+}