AspectRatioFitterEditor.cs

using UnityEngine;
using UnityEditor.AnimatedValues;
using UnityEditor.SceneManagement;
using UnityEngine.UI;

namespace UnityEditor.UI
{
    [CustomEditor(typeof(AspectRatioFitter), true)]
    [CanEditMultipleObjects]
    /// <summary>
    ///   Custom Editor for the AspectRatioFitter component.
    ///   Extend this class to write a custom editor for a component derived from AspectRatioFitter.
    /// </summary>
    public class AspectRatioFitterEditor : SelfControllerEditor
    {
        SerializedProperty m_AspectMode;
        SerializedProperty m_AspectRatio;


        AnimBool m_ModeBool;
        private AspectRatioFitter aspectRatioFitter;

        protected virtual void OnEnable()
        {
            m_AspectMode = serializedObject.FindProperty("m_AspectMode");
            m_AspectRatio = serializedObject.FindProperty("m_AspectRatio");
            aspectRatioFitter = target as AspectRatioFitter;

            m_ModeBool = new AnimBool(m_AspectMode.intValue != 0);
            m_ModeBool.valueChanged.AddListener(Repaint);
        }

        public override void OnInspectorGUI()
        {
            serializedObject.Update();
            EditorGUILayout.PropertyField(m_AspectMode);

            m_ModeBool.target = m_AspectMode.intValue != 0;

            if (EditorGUILayout.BeginFadeGroup(m_ModeBool.faded))
                EditorGUILayout.PropertyField(m_AspectRatio);
            EditorGUILayout.EndFadeGroup();

            serializedObject.ApplyModifiedProperties();

            if (aspectRatioFitter)
            {
                if (!aspectRatioFitter.IsAspectModeValid() && !IsEditingPrefabAssetOrInPrefabMode())
                    ShowNoParentWarning();
                if (!aspectRatioFitter.IsComponentValidOnObject())
                    ShowCanvasRenderModeInvalidWarning();
            }

            base.OnInspectorGUI();
        }

        protected virtual void OnDisable()
        {
            aspectRatioFitter = null;
            m_ModeBool.valueChanged.RemoveListener(Repaint);
        }

        private static void ShowNoParentWarning()
        {
            var text = L10n.Tr("You cannot use this Aspect Mode because this Component's GameObject does not have a parent object.");
            EditorGUILayout.HelpBox(text, MessageType.Warning, true);
        }

        private static void ShowCanvasRenderModeInvalidWarning()
        {
            var text = L10n.Tr("You cannot use this Aspect Mode because this Component is attached to a Canvas with a fixed width and height.");
            EditorGUILayout.HelpBox(text, MessageType.Warning, true);
        }

        // Returns true if any of this editor's targets is being edited in a Prefab Stage
        // (Prefab Mode) or is a prefab asset from the Project window.
        private bool IsEditingPrefabAssetOrInPrefabMode()
        {
            foreach (var t in targets)
            {
                var go = (t as GameObject) ?? (t as Component)?.gameObject;
                if (go == null)
                    continue;

                // In Prefab Mode (either Isolation or In Context)?
                if (PrefabStageUtility.GetPrefabStage(go) != null)
                    return true;

                // Prefab asset in Project window?
                if (PrefabUtility.IsPartOfPrefabAsset(go))
                    return true;
            }

            return false;
        }
    }
}