Unity Editor Script to select an animation in the AnimationWindow when a state is selected in the AnimatorWindow

AutoSelectAnimation.cs

// Copyright Fleeting Being
// MIT license - https://opensource.org/licenses/MIT
// Inspired by AstralByte's AutoHideUILayer 
// https://www.reddit.com/r/Unity3D/comments/6yaiit/free_editor_script_to_automatically_hide_ui_layer/
using System.Linq;
using UnityEditor;
using UnityEditor.Animations;
using UnityEngine;

namespace Plugins.AutoSelectAnimation.Editor
{
  /// <summary>
  /// Automatically select the animation of the selected animator state
  ///<para></para>
  /// Installation: put in any folder named "Editor". Requires Unity 5.2 or later (for Selection.selectionChanged).
  /// </summary>
  [InitializeOnLoad]
  internal static class AutoSelectAnimation
  {
    /************************************************************************************************************************/

    const string EnabledToggleMenuPath = "Edit/Auto Select Animation";

    static bool _isEnabled;

    /************************************************************************************************************************/

    static AutoSelectAnimation()
    {
      EditorApplication.delayCall += () =>
      {
        _isEnabled = EditorPrefs.GetBool(EnabledToggleMenuPath, true);

        if (!_isEnabled) return;

        Selection.selectionChanged += OnSelectionChanged;
        EditorApplication.playModeStateChanged += OnSelectionChanged;
      };
    }

    /************************************************************************************************************************/

    [MenuItem(EnabledToggleMenuPath, validate = true)]
    static bool ValidateToggleEnabled()
    {
      Menu.SetChecked(EnabledToggleMenuPath, _isEnabled);
      return true;
    }

    [MenuItem(EnabledToggleMenuPath, priority = 200)]
    static void ToggleEnabled()
    {
      _isEnabled = !_isEnabled;
      EditorPrefs.SetBool(EnabledToggleMenuPath, _isEnabled);

      if (_isEnabled)
      {
        Selection.selectionChanged += OnSelectionChanged;
        EditorApplication.playModeStateChanged += OnSelectionChanged;
        OnSelectionChanged();
      }
      else
      {
        Selection.selectionChanged -= OnSelectionChanged;
        EditorApplication.playModeStateChanged -= OnSelectionChanged;
      }
    }

    /************************************************************************************************************************/

    static void OnSelectionChanged()
    {
      // Check if the animation window is open.
      if (!EditorWindow.HasOpenInstances<AnimationWindow>()) return;

      // Get the animation window.
      AnimationWindow window = EditorWindow.GetWindow<AnimationWindow>();

      // Check if we have a window.
      if (!window) return;

      // Check that no sensitive operations are in progress.
      if (window.playing || window.recording) return;

      // Get the selected animator state's clip
      AnimationClip selection =
        Selection.objects.OfType<AnimatorState>()
                 .Select(s => s.motion)
                 .OfType<AnimationClip>()
                 .FirstOrDefault();

      if (!selection) return;

      window.animationClip = selection;
    }

    static void OnSelectionChanged(PlayModeStateChange sc)
    {
      OnSelectionChanged();
    }
    /************************************************************************************************************************/
  }
}