private void EditingAnActivity()
        {
            _editorEffector.SpUpdate();

            CreateActivityToolbarArea();

            GUILayout.Space(singleLineHeight * 4);
            _scrollPos = GUILayout.BeginScrollView(_scrollPos, GUILayout.Height(position.height - singleLineHeight * 4));
            switch (_editorEffector.CurrentActivityMode())
            {
            case ActivityEditorMode.PreventEyesBlinking:
                _layoutPreventEyesBlinking.Layout(position);
                break;

            case ActivityEditorMode.AdditionalEditors:
                switch (_editorEffector.GetAdditionalEditor())
                {
                case AdditionalEditorsMode.CreateBlendTrees:
                    _layoutManipulateTrees.LayoutAssetCreator(position);
                    break;

                case AdditionalEditorsMode.ViewBlendTrees:
                    _layoutManipulateTrees.LayoutTreeViewer(position);
                    break;

                case AdditionalEditorsMode.CombineFaceExpressions:
                    _layoutFaceExpressionCombiner.Layout(Repaint);
                    break;

                default:
                    throw new ArgumentOutOfRangeException();
                }
                break;

            case ActivityEditorMode.OtherOptions:
                _layoutOtherOptions.Layout(Repaint, position);
                break;

            // ReSharper disable once RedundantCaseLabel
            case ActivityEditorMode.SetFaceExpressions:
            default:
                _layoutSetFaceExpressions.Layout(position);
                break;
            }
            GUILayout.EndScrollView();

            _editorEffector.ApplyModifiedProperties();
        }