spine-runtimes/spine-flutter/example/lib/ik_following.dart

///
/// Spine Runtimes License Agreement
/// Last updated July 28, 2023. Replaces all prior versions.
///
/// Copyright (c) 2013-2023, Esoteric Software LLC
///
/// Integration of the Spine Runtimes into software or otherwise creating
/// derivative works of the Spine Runtimes is permitted under the terms and
/// conditions of Section 2 of the Spine Editor License Agreement:
/// http://esotericsoftware.com/spine-editor-license
///
/// Otherwise, it is permitted to integrate the Spine Runtimes into software or
/// otherwise create derivative works of the Spine Runtimes (collectively,
/// "Products"), provided that each user of the Products must obtain their own
/// Spine Editor license and redistribution of the Products in any form must
/// include this license and copyright notice.
///
/// THE SPINE RUNTIMES ARE PROVIDED BY ESOTERIC SOFTWARE LLC "AS IS" AND ANY
/// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
/// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
/// DISCLAIMED. IN NO EVENT SHALL ESOTERIC SOFTWARE LLC BE LIABLE FOR ANY
/// DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
/// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES,
/// BUSINESS INTERRUPTION, OR LOSS OF USE, DATA, OR PROFITS) HOWEVER CAUSED AND
/// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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///

import 'package:spine_flutter/spine_flutter.dart';
import 'package:flutter/material.dart';

class IkFollowing extends StatefulWidget {
  const IkFollowing({Key? key}) : super(key: key);

  @override
  IkFollowingState createState() => IkFollowingState();
}

class IkFollowingState extends State<IkFollowing> {
  late SpineWidgetController controller;
  Offset? crossHairPosition;

  @override
  void initState() {
    super.initState();

    controller = SpineWidgetController(onInitialized: (controller) {
      // Set the walk animation on track 0, let it loop
      controller.animationState.setAnimationByName(0, "walk", true);
      controller.animationState.setAnimationByName(1, "aim", true);
    }, onAfterUpdateWorldTransforms: (controller) {
      final worldPosition = crossHairPosition;
      if (worldPosition == null) return;
      final bone = controller.skeleton.findBone("crosshair")!;
      final parent = bone.getParent()!;
      final position = parent.worldToLocal(worldPosition.dx, worldPosition.dy);
      bone.setX(position.x);
      bone.setY(position.y);
    });
  }

  void _updateBonePosition(Offset position) {
    crossHairPosition = controller.toSkeletonCoordinates(position);
  }

  @override
  Widget build(BuildContext context) {
    reportLeaks();

    return Scaffold(
        appBar: AppBar(title: const Text('IK Following')),
        body: GestureDetector(
          onPanDown: (drag) => _updateBonePosition(drag.localPosition),
          onPanUpdate: (drag) => _updateBonePosition(drag.localPosition),
          child: SpineWidget.fromAsset("assets/spineboy.atlas", "assets/spineboy-pro.skel", controller, alignment: Alignment.centerLeft,),
        ));
  }
}