sample flutter changes for discussion

lib/src/rive_core/animation/nested_simple_animation.dart

@@ -29,4 +29,12 @@ class NestedSimpleAnimation extends NestedSimpleAnimationBase {
     }
     super.advance(elapsedSeconds, mountedArtboard);
   }
+
+  void goTo(double time, MountedArtboard mountedArtboard) {
+    if (isPlaying) {
+      linearAnimationInstance?.goto(time);
+      linearAnimationInstance?.apply(mountedArtboard, mix);
+      linearAnimationInstance?.needsApply = false;
+    }
+  }
 }

lib/src/rive_core/artboard.dart

@@ -153,21 +153,30 @@ class Artboard extends ArtboardBase with ShapePaintContainer {
   }
 
   final Set<NestedArtboard> _activeNestedArtboards = {};
+  Set<NestedArtboard> get activeNestedArtboards => _activeNestedArtboards;
 
   /// Update any dirty components in this artboard.
   bool advance(double elapsedSeconds, {bool nested = false}) {
     bool didUpdate = false;
+    bool handleNestedArtboards = true;
+
     for (final controller in _animationControllers) {
+      if (controller.suppressesNestedArtboards) {
+        handleNestedArtboards = false;
+      }
       if (controller.isActive) {
         controller.apply(context, elapsedSeconds);
         didUpdate = true;
       }
     }
+    // NOTE: i think this works out if the nested artboard should still be
+    // animating...
     if (updateComponents() || didUpdate) {
       didUpdate = true;
     }
 
-    if (nested) {
+    // TODO: talk about this.
+    if (nested && handleNestedArtboards) {
       var active = _activeNestedArtboards.toList(growable: false);
       for (final activeNestedArtboard in active) {
         activeNestedArtboard.advance(elapsedSeconds);

lib/src/rive_core/nested_artboard.dart

@@ -1,5 +1,6 @@
 import 'dart:ui';
 
+import 'package:rive/rive.dart';
 import 'package:rive/src/core/core.dart';
 import 'package:rive/src/generated/nested_artboard_base.dart';
 import 'package:rive/src/rive_core/animation/nested_remap_animation.dart';
@@ -46,7 +47,6 @@ class NestedArtboard extends NestedArtboardBase {
   @override
   void artboardIdChanged(int from, int to) {}
 
-
   @override
   void childAdded(Component child) {
     super.childAdded(child);
@@ -88,6 +88,22 @@ class NestedArtboard extends NestedArtboardBase {
     mountedArtboard!.advance(elapsedSeconds);
   }
 
+  void goTo(double seconds) {
+    if (mountedArtboard == null) {
+      return;
+    }
+    for (final animation in _animations) {
+      if (animation.isEnabled) {
+        if (animation is NestedSimpleAnimation) {
+          animation.goTo(seconds, mountedArtboard!);
+        }
+      }
+    }
+    // Gotta advance the artboard to make it dirty?
+    // (if we skip this no redraw)
+    mountedArtboard!.advance(0.0);
+  }
+
   @override
   void update(int dirt) {
     super.update(dirt);

lib/src/rive_core/rive_animation_controller.dart

@@ -6,6 +6,14 @@ abstract class RiveAnimationController<T> {
   final _isActive = ValueNotifier<bool>(false);
   ValueListenable<bool> get isActiveChanged => _isActive;
 
+  // TODO: this is a hack.
+  // Ideally nestedArtboards are not run in the Artboard.advance, but instead
+  // always controlled by AnimationControllers.
+  // SimpleAnimationControllers kinda throw a spanner in the works here.
+  // unless we do some magic that means multiple simple animation controllers
+  // won't all compete for advancing the nested artboard....
+  final suppressesNestedArtboards = false;
+
   bool get isActive => _isActive.value;
   set isActive(bool value) {
     if (_isActive.value != value) {