refactor(srp): add renderer backend registry seam

engine/src/Rendering/Internal/RenderPipelineFactory.cpp

@@ -4,12 +4,55 @@
 #include "Rendering/Pipelines/ManagedScriptableRenderPipelineAsset.h"
 #include "Rendering/Pipelines/ScriptableRenderPipelineHost.h"
 
+#include <mutex>
+#include <unordered_map>
+#include <unordered_set>
+
 namespace XCEngine {
 namespace Rendering {
 namespace Internal {
 
 namespace {
 
+std::shared_ptr<const RenderPipelineAsset>
+CreateBuiltinForwardPipelineRendererAsset() {
+    static const std::shared_ptr<const RenderPipelineAsset>
+        s_builtinForwardPipelineAsset =
+            std::make_shared<Pipelines::BuiltinForwardPipelineAsset>();
+    return s_builtinForwardPipelineAsset;
+}
+
+using PipelineRendererAssetRegistry =
+    std::unordered_map<std::string, PipelineRendererAssetFactory>;
+
+PipelineRendererAssetRegistry& GetPipelineRendererAssetRegistry() {
+    static PipelineRendererAssetRegistry registry = {};
+    return registry;
+}
+
+std::unordered_set<std::string>& GetBuiltinPipelineRendererAssetKeys() {
+    static std::unordered_set<std::string> builtinKeys = {};
+    return builtinKeys;
+}
+
+std::mutex& GetPipelineRendererAssetRegistryMutex() {
+    static std::mutex mutex;
+    return mutex;
+}
+
+void EnsureBuiltinPipelineRendererAssetRegistryInitialized() {
+    static const bool initialized = []() {
+        PipelineRendererAssetRegistry& registry =
+            GetPipelineRendererAssetRegistry();
+        registry.emplace(
+            "BuiltinForward",
+            &CreateBuiltinForwardPipelineRendererAsset);
+        GetBuiltinPipelineRendererAssetKeys().insert("BuiltinForward");
+        return true;
+    }();
+    (void)initialized;
+}
+
 std::unique_ptr<NativeSceneRenderer> TryCreateNativeSceneRendererFromAsset(
     const std::shared_ptr<const RenderPipelineAsset>& asset) {
     if (asset == nullptr) {
@@ -41,16 +84,64 @@ std::shared_ptr<const RenderPipelineAsset> CreateFallbackRenderPipelineAsset() {
     return std::make_shared<Pipelines::ScriptableRenderPipelineHostAsset>();
 }
 
-std::shared_ptr<const RenderPipelineAsset> CreatePipelineRendererAssetByKey(
-    const std::string& key) {
-    if (key == "BuiltinForward") {
-        static const std::shared_ptr<const RenderPipelineAsset>
-            s_builtinForwardPipelineAsset =
-                std::make_shared<Pipelines::BuiltinForwardPipelineAsset>();
-        return s_builtinForwardPipelineAsset;
+bool RegisterPipelineRendererAssetFactory(
+    const std::string& key,
+    PipelineRendererAssetFactory factory) {
+    if (key.empty() || !factory) {
+        return false;
     }
 
-    return nullptr;
+    EnsureBuiltinPipelineRendererAssetRegistryInitialized();
+
+    std::lock_guard<std::mutex> lock(
+        GetPipelineRendererAssetRegistryMutex());
+    PipelineRendererAssetRegistry& registry =
+        GetPipelineRendererAssetRegistry();
+    if (registry.find(key) != registry.end()) {
+        return false;
+    }
+
+    registry.emplace(key, std::move(factory));
+    return true;
+}
+
+bool UnregisterPipelineRendererAssetFactory(const std::string& key) {
+    if (key.empty()) {
+        return false;
+    }
+
+    EnsureBuiltinPipelineRendererAssetRegistryInitialized();
+
+    std::lock_guard<std::mutex> lock(
+        GetPipelineRendererAssetRegistryMutex());
+    if (GetBuiltinPipelineRendererAssetKeys().find(key) !=
+        GetBuiltinPipelineRendererAssetKeys().end()) {
+        return false;
+    }
+
+    PipelineRendererAssetRegistry& registry =
+        GetPipelineRendererAssetRegistry();
+    return registry.erase(key) != 0u;
+}
+
+std::shared_ptr<const RenderPipelineAsset> CreatePipelineRendererAssetByKey(
+    const std::string& key) {
+    if (key.empty()) {
+        return nullptr;
+    }
+
+    EnsureBuiltinPipelineRendererAssetRegistryInitialized();
+
+    std::lock_guard<std::mutex> lock(
+        GetPipelineRendererAssetRegistryMutex());
+    const PipelineRendererAssetRegistry& registry =
+        GetPipelineRendererAssetRegistry();
+    const auto it = registry.find(key);
+    if (it == registry.end() || !it->second) {
+        return nullptr;
+    }
+
+    return it->second();
 }
 
 std::shared_ptr<const RenderPipelineAsset> ResolveRenderPipelineAssetOrDefault(

engine/src/Rendering/Internal/RenderPipelineFactory.h

@@ -1,7 +1,8 @@
 #pragma once
 
-#include <string>
+#include <functional>
 #include <memory>
+#include <string>
 
 namespace XCEngine {
 namespace Rendering {
@@ -12,8 +13,15 @@ class RenderPipelineAsset;
 
 namespace Internal {
 
+using PipelineRendererAssetFactory =
+    std::function<std::shared_ptr<const RenderPipelineAsset>()>;
+
 std::shared_ptr<const RenderPipelineAsset> CreateConfiguredRenderPipelineAsset();
 std::shared_ptr<const RenderPipelineAsset> CreateFallbackRenderPipelineAsset();
+bool RegisterPipelineRendererAssetFactory(
+    const std::string& key,
+    PipelineRendererAssetFactory factory);
+bool UnregisterPipelineRendererAssetFactory(const std::string& key);
 std::shared_ptr<const RenderPipelineAsset> CreatePipelineRendererAssetByKey(
     const std::string& key);