data/Packages/com.unity.render-pipelines.universal/Runtime/RendererFeatures/FullScreenPassRendererFeature.migration.cs

using UnityEditor;
using UnityEngine.Scripting.APIUpdating;

namespace UnityEngine.Rendering.Universal
{
    [MovedFrom("")]
    public partial class FullScreenPassRendererFeature : ISerializationCallbackReceiver
    {
        private enum Version
        {
            // * Uninitialised is a special last entry that will only ever be set on newly created objects or objects
            //   which were previously serialised with no Version member at all.
            // * We distinguish between new objects and the unversioned objects based on if we first see this value during
            //   serialization or during deserialization respectively.
            Uninitialised = -1,

            Initial,
            AddFetchColorBufferCheckbox,

            // These two entries should remain at the end of the enum and new version should be added before Count
            Count,
            Latest = Count - 1,
        }

        [SerializeField]
        [HideInInspector]
        private Version m_Version = Version.Uninitialised;

        private void UpgradeIfNeeded()
        {
            // As we rely on serialization/deserialization order to initialize the version as player might have restricions
            // on when and if serialization is done skipping any upgrading at runtime to avoid accidentally doing the
            // upgrade on the latest version. Upgrading at runtime does not really have much utility as it would mean
            // that the asset would need to have been produced in an editor which is an earlier build version than the player
    #if UNITY_EDITOR
            if (m_Version == Version.Latest)
                return;

            if(m_Version == Version.Initial)
            {
                // * Previously the ScriptableRenderPassInput.Color requirement was repurposed to mean "copy the active
                //   color target" even though it is typically used to request '_CameraOpaqueTexture' and the copy color pass.
                // * From now on, the "Fetch Color Buffer" choice will be a separate checkbox to remove the inconsistent
                //   meaning and to allow using the '_CameraOpaqueTexture' if one wants to as well.
                fetchColorBuffer = requirements.HasFlag(ScriptableRenderPassInput.Color);

                // As the Color flag was being masked out during actual rendering we can safely disable it.
                requirements &= ~ScriptableRenderPassInput.Color;

                m_Version++;
            }
            // Put the next upgrader in an "if" here (not "else if" as they migh all need to run)

            // Making sure SetDirty is called once after deserialization
            EditorApplication.delayCall += () =>
            {
                if (this)
                    EditorUtility.SetDirty(this);
            };
    #endif
        }

        /// <inheritdoc/>
        void ISerializationCallbackReceiver.OnBeforeSerialize()
        {
            // This should only ever be true the first time we're serializing a newly created object
            if (m_Version == Version.Uninitialised)
                m_Version = Version.Latest;
        }

        /// <inheritdoc/>
        void ISerializationCallbackReceiver.OnAfterDeserialize()
        {
            // The 'Uninitialised' version is expected to only occur during deserialization for objects that were previously
            // serialized before we added the m_Version field
            if (m_Version == Version.Uninitialised)
                m_Version = Version.Initial;

            UpgradeIfNeeded();
        }
    }
}