refactor(srp): formalize universal renderer selection and caching

managed/XCEngine.ScriptCore/Rendering/Universal/UniversalRenderPipelineAsset.cs

@@ -15,10 +15,8 @@ namespace XCEngine.Rendering.Universal
 
         protected override ScriptableRenderPipeline CreatePipeline()
         {
-            ScriptableRendererData resolvedRendererData =
-                ResolveDefaultRendererData();
-            return resolvedRendererData != null
-                ? new UniversalRenderPipeline(resolvedRendererData)
+            return GetDefaultRendererData() != null
+                ? new UniversalRenderPipeline(this)
                 : null;
         }
 
@@ -26,7 +24,7 @@ namespace XCEngine.Rendering.Universal
             CameraRenderRequestContext context)
         {
             ScriptableRendererData resolvedRendererData =
-                ResolveDefaultRendererData();
+                GetDefaultRendererData();
             if (resolvedRendererData != null)
             {
                 resolvedRendererData.ConfigureCameraRenderRequestInstance(
@@ -37,38 +35,86 @@ namespace XCEngine.Rendering.Universal
         protected override string GetPipelineRendererAssetKey()
         {
             ScriptableRendererData resolvedRendererData =
-                ResolveDefaultRendererData();
+                GetDefaultRendererData();
             return resolvedRendererData != null
                 ? resolvedRendererData.GetPipelineRendererAssetKeyInstance()
                 : string.Empty;
         }
 
-        private ScriptableRendererData ResolveDefaultRendererData()
+        internal ScriptableRendererData GetDefaultRendererData()
         {
-            if (rendererDataList == null ||
-                rendererDataList.Length == 0)
+            return GetRendererData(defaultRendererIndex);
+        }
+
+        internal ScriptableRenderer GetDefaultRenderer()
+        {
+            return GetRenderer(defaultRendererIndex);
+        }
+
+        internal ScriptableRendererData GetRendererData(
+            int rendererIndex)
+        {
+            EnsureRendererDataList();
+            int resolvedRendererIndex =
+                ResolveRendererIndex(rendererIndex);
+            if (rendererDataList[resolvedRendererIndex] == null)
             {
-                rendererDataList =
-                    new ScriptableRendererData[]
-                    {
-                        new UniversalRendererData()
-                    };
-                defaultRendererIndex = 0;
+                rendererDataList[resolvedRendererIndex] =
+                    new UniversalRendererData();
             }
 
+            return rendererDataList[resolvedRendererIndex];
+        }
+
+        internal ScriptableRenderer GetRenderer(
+            int rendererIndex)
+        {
+            ScriptableRendererData rendererData =
+                GetRendererData(rendererIndex);
+            return rendererData != null
+                ? rendererData.GetRendererInstance()
+                : null;
+        }
+
+        private void EnsureRendererDataList()
+        {
+            if (rendererDataList != null &&
+                rendererDataList.Length > 0)
+            {
+                return;
+            }
+
+            rendererDataList =
+                new ScriptableRendererData[]
+                {
+                    new UniversalRendererData()
+                };
+            defaultRendererIndex = 0;
+        }
+
+        private int ResolveRendererIndex(
+            int rendererIndex)
+        {
+            EnsureRendererDataList();
+            if (rendererIndex < 0 ||
+                rendererIndex >= rendererDataList.Length)
+            {
+                return ResolveDefaultRendererIndex();
+            }
+
+            return rendererIndex;
+        }
+
+        private int ResolveDefaultRendererIndex()
+        {
+            EnsureRendererDataList();
             if (defaultRendererIndex < 0 ||
                 defaultRendererIndex >= rendererDataList.Length)
             {
                 defaultRendererIndex = 0;
             }
 
-            if (rendererDataList[defaultRendererIndex] == null)
-            {
-                rendererDataList[defaultRendererIndex] =
-                    new UniversalRendererData();
-            }
-
-            return rendererDataList[defaultRendererIndex];
+            return defaultRendererIndex;
         }
     }
 }