Upgrading pool pattern

_Design/glossary.md

@@ -3,34 +3,55 @@
 ## ResourceRegistry
 
 A ResourceRegistry owns GPU-backed resources on the caller's behalf and hands out
-lightweight Handles instead of pointers or ownership.
+lightweight Handles instead of pointers or ownership. It is engine-internal:
+frontend code never sees it, and reaches it through a ResourceRegistryRef.
 
-Internally it's a collection of per-type pools, each responsible for one
-resource type:
+Internally it's a collection of per-type pools, each a `Pool<T, Handle>`
+(a generation-checked slot pool). A type that needs extra behaviour wraps its
+pool in a thin class instead:
 
 ```
 ResourceRegistry
- ├── MeshPool     → MeshHandle
- ├── TexturePool  → TextureHandle   (planned)
- └── MaterialPool → MaterialHandle  (planned)
+ ├── meshes        Pool<Mesh, MeshHandle>
+ ├── renderTargets RenderTargetPool → RenderTargetHandle
+ │                 (wraps Pool; waits for the GPU on release, applies resizes)
+ ├── scenes        Pool<Scene, SceneHandle>
+ ├── textures      (planned)
+ └── materials     (planned)
 ```
 
+Engine code (`Application`, `ImGuiRenderer`, `SceneRenderer`) uses the pools
+directly, e.g. `resources.renderTargets.get(handle)`.
+
 A Handle is a small (index, generation) pair. The index locates the slot in
 the pool; the generation is bumped when that slot is released, so a Handle
 kept around after release() is detected as stale instead of resolving to
 someone else's resource (or freed memory).
 
+Think: "Where does the engine keep every GPU resource, and how does it look one
+up by handle?"
+
+## ResourceRegistryRef
+
+A ResourceRegistryRef is the frontend's non-owning, cheap-to-copy view of the
+ResourceRegistry, returned by `Application::resources()`. It exposes only what
+frontend code needs and hands out no pools, so no Vulkan-facing types leak
+through the public API:
+
+```
+create<T>(...)   load<T>(path)   release<T>(handle)
+requestResize(target, w, h)   getExtent(target)   isAlive(handle)
+```
+
 Typical lifecycle:
 
 ```
 load<Mesh>(path) / create<Mesh>(...)  →  MeshHandle
                                         │
-                        get<Mesh>(handle)  →  const Mesh&
-                                        │
                         release<Mesh>(handle)
 ```
 
-Think: "Where do I get or release a GPU resource by handle, without owning its
+Think: "How do I create or release a GPU resource by handle, without owning its
 lifetime directly?"
 
 ## Buffer
@@ -257,7 +278,7 @@ A PanelRegistry owns Panels on the caller's behalf and hands out lightweight
 PanelHandles instead of pointers or ownership.
 
 Internally it's a generation-checked slot pool, the same shape ResourceRegistry's
-per-type pools use:
+`Pool<T, Handle>` uses:
 
 ```
 PanelRegistry

engine/include/sophia/application.hpp

@@ -7,7 +7,7 @@
 #include <sophia/canvas.hpp>
 #include <sophia/console/console_command_registry.hpp>
 #include <sophia/frame_info.hpp>
-#include <sophia/resource_registry.hpp>
+#include <sophia/resource_registry_ref.hpp>
 #include <sophia/types.hpp>
 #include <sophia/ui/debug_ui.hpp>
 #include <sophia/ui/panel_registry.hpp>
@@ -45,7 +45,7 @@ class Application {
   virtual void onRender() {}
   virtual void onDestroy() {}
 
-  ResourceRegistry& resources() { return this->resourceRegistry; }
+  ResourceRegistryRef resources();
   PanelRegistry& panels() { return this->panelRegistry; }
   UI& ui() { return this->_ui; }
 
@@ -62,7 +62,7 @@ class Application {
   /**
    * Chooses where the scene is rendered. An invalid handle (the default) means
    * the swapchain; a target created with
-   * ResourceRegistry::create<RenderTarget>() redirects it offscreen, and the
+   * ResourceRegistryRef::create<RenderTarget>() redirects it offscreen, and the
    * swapchain then only receives the UI. FrameInfo::currentFramebufferExtent
    * and the camera projection follow the target's size.
    */
@@ -77,7 +77,6 @@ class Application {
   class Impl;
   std::unique_ptr<Impl> impl;
 
-  ResourceRegistry resourceRegistry;
   PanelRegistry panelRegistry;
   UI _ui;
 

engine/include/sophia/components.hpp

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <sophia/resource_registry.hpp>
+#include <sophia/handles.hpp>
 #include <string>
 
 #define GLM_FORCE_RADIANS

engine/include/sophia/handles.hpp

@@ -27,9 +27,11 @@ struct Handle {
 struct MeshTag {};
 struct PanelTag {};
 struct RenderTargetTag {};
+struct SceneTag {};
 
 using MeshHandle = Handle<MeshTag>;
 using PanelHandle = Handle<PanelTag>;
 using RenderTargetHandle = Handle<RenderTargetTag>;
+using SceneHandle = Handle<SceneTag>;
 
 }  // namespace sophia

engine/include/sophia/resource_registry_ref.hpp

@@ -1,25 +1,23 @@
 #pragma once
 
-#include <memory>
+#include <sophia/canvas.hpp>
 #include <sophia/handles.hpp>
+#include <sophia/types.hpp>
 #include <string>
 #include <type_traits>
 #include <utility>
 #include <vector>
 
-#include "sophia/canvas.hpp"
-#include "sophia/types.hpp"
-
 #define GLM_FORCE_RADIANS
 #define GLM_FORCE_DEPTH_ZERO_TO_ONE
 #include <glm/glm.hpp>
 
 namespace sophia {
 
-class Device;
 class Mesh;
 class RenderTarget;
-class ImGuiRenderer;
+class Scene;
+class ResourceRegistry;
 
 template <typename T>
 struct ResourceTraits;
@@ -34,13 +32,13 @@ struct ResourceTraits<RenderTarget> {
   using Handle = RenderTargetHandle;
 };
 
-class ResourceRegistry {
+template <>
+struct ResourceTraits<Scene> {
+  using Handle = SceneHandle;
+};
+
+class ResourceRegistryRef {
  public:
-  ~ResourceRegistry();
-
-  ResourceRegistry(const ResourceRegistry&) = delete;
-  ResourceRegistry& operator=(const ResourceRegistry&) = delete;
-
   template <typename T>
   typename ResourceTraits<T>::Handle load(const std::string& path);
 
@@ -54,21 +52,16 @@ class ResourceRegistry {
   glm::vec2 getExtent(RenderTargetHandle handle) const;
 
   bool isAlive(RenderTargetHandle handle) const;
+  bool isAlive(SceneHandle handle) const;
 
-  /**
-   * Waits for the GPU to go idle, so don't call this every frame. Don't release
-   * the target the scene is currently rendering into.
-   */
   template <typename T>
   void release(typename ResourceTraits<T>::Handle handle);
 
  private:
   friend class Application;
-  friend class ImGuiRenderer;
 
-  // `renderTargetFormat` is a VkFormat value; it must match the color format
-  // the scene pipelines are built against.
-  ResourceRegistry(Device& device, u32 renderTargetFormat);
+  explicit ResourceRegistryRef(ResourceRegistry& registry)
+      : registry{&registry} {}
 
   MeshHandle createResource(std::type_identity<Mesh>,
                             std::vector<CanvasVertex> vertices,
@@ -77,27 +70,21 @@ class ResourceRegistry {
   RenderTargetHandle createResource(std::type_identity<RenderTarget>,
                                     u32 width = 1, u32 height = 1);
 
-  RenderTarget& getRenderTarget(RenderTargetHandle handle);
-  const RenderTarget& getRenderTarget(RenderTargetHandle handle) const;
-  void applyPendingResizes();
+  SceneHandle createResource(std::type_identity<Scene>);
 
-  template <typename T>
-  const T& get(typename ResourceTraits<T>::Handle handle) const;
-
-  class Impl;
-  std::unique_ptr<Impl> impl;
+  ResourceRegistry* registry;
 };
 
 template <>
-MeshHandle ResourceRegistry::load<Mesh>(const std::string& path);
+MeshHandle ResourceRegistryRef::load<Mesh>(const std::string& path);
 
 template <>
-void ResourceRegistry::release<Mesh>(MeshHandle handle);
+void ResourceRegistryRef::release<Mesh>(MeshHandle handle);
 
 template <>
-void ResourceRegistry::release<RenderTarget>(RenderTargetHandle handle);
+void ResourceRegistryRef::release<RenderTarget>(RenderTargetHandle handle);
 
 template <>
-const Mesh& ResourceRegistry::get<Mesh>(MeshHandle handle) const;
+void ResourceRegistryRef::release<Scene>(SceneHandle handle);
 
 }  // namespace sophia

engine/include/sophia/ui/ui.hpp

@@ -3,11 +3,11 @@
 #include <imgui.h>
 
 #include <sophia/handles.hpp>
+#include <sophia/resource_registry_ref.hpp>
 
 namespace sophia {
 
 class ImGuiRenderer;
-class ResourceRegistry;
 
 class UI {
  public:
@@ -31,9 +31,9 @@ class UI {
  private:
   friend class Application;
 
-  explicit UI(ResourceRegistry& resources) : resources{resources} {}
+  explicit UI(ResourceRegistryRef resources) : resources{resources} {}
 
-  ResourceRegistry& resources;
+  ResourceRegistryRef resources;
   ImGuiRenderer* renderer = nullptr;
 };
 

engine/src/imgui_renderer.cpp

@@ -92,7 +92,7 @@ void ImGuiRenderer::beginFrame() {
 
 ImTextureID ImGuiRenderer::getTextureId(RenderTargetHandle handle) {
   vk::ImageView view =
-      std::as_const(resources).getRenderTarget(handle).getImage().getView();
+      resources.renderTargetPool.get(handle).getImage().getView();
 
   auto it = textures.find(handle.index);
   if (it != textures.end()) {
@@ -116,10 +116,11 @@ ImTextureID ImGuiRenderer::getTextureId(RenderTargetHandle handle) {
 void ImGuiRenderer::releaseStaleTextures() {
   for (auto it = textures.begin(); it != textures.end();) {
     RenderTargetHandle handle{it->first, it->second.generation};
+    RenderTargetPool& renderTargetPool = resources.renderTargetPool;
+
     bool stale =
-        !resources.isAlive(handle) ||
-        std::as_const(resources).getRenderTarget(handle).getImage().getView() !=
-            it->second.view;
+        !renderTargetPool.isAlive(handle) ||
+        renderTargetPool.get(handle).getImage().getView() != it->second.view;
     if (stale) {
       ImGui_ImplVulkan_RemoveTexture(it->second.descriptorSet);
       it = textures.erase(it);

engine/src/imgui_renderer.hpp

@@ -3,12 +3,12 @@
 #include <imgui.h>
 
 #include <sophia/handles.hpp>
-#include <sophia/resource_registry.hpp>
 #include <sophia/types.hpp>
 #include <sophia/ui/dock_layout.hpp>
 #include <unordered_map>
 
 #include "device.hpp"
+#include "resources/resource_registry.hpp"
 #include "window.hpp"
 
 namespace sophia {

engine/src/mesh.hpp

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <memory>
-#include <sophia/resource_registry.hpp>
+#include <sophia/handles.hpp>
 #include <sophia/types.hpp>
 #include <vector>
 

engine/src/resources/pools/mesh_pool.cpp

@@ -1,58 +0,0 @@
-#include "resources/pools/mesh_pool.hpp"
-
-#include <sophia/util/assert.hpp>
-
-namespace sophia {
-
-namespace {
-constexpr u32 GENERATION_MASK = (1u << 12) - 1;
-}  // namespace
-
-MeshPool::MeshPool(Device& device) : device{device} {}
-
-MeshPool::~MeshPool() = default;
-
-MeshHandle MeshPool::create(const Mesh::Builder& builder) {
-  auto mesh = std::make_unique<Mesh>(device, builder);
-
-  if (!freeList.empty()) {
-    u32 index = freeList.back();
-    freeList.pop_back();
-    slots[index].mesh = std::move(mesh);
-    return MeshHandle{index, slots[index].generation};
-  }
-
-  slots.push_back(Slot{std::move(mesh), 0});
-  return MeshHandle{static_cast<u32>(slots.size() - 1), 0};
-}
-
-const Mesh& MeshPool::get(MeshHandle handle) const {
-  SOPHIA_ASSERT(handle.isValid(), "invalid MeshHandle");
-  SOPHIA_ASSERT(handle.index < slots.size(),
-                "MeshHandle index out of range:", handle.index);
-
-  const Slot& slot = slots[handle.index];
-  SOPHIA_ASSERT(slot.generation == handle.generation,
-                "stale MeshHandle (generation mismatch):", handle.index);
-  SOPHIA_ASSERT(slot.mesh != nullptr,
-                "MeshHandle refers to a released mesh:", handle.index);
-  return *slot.mesh;
-}
-
-void MeshPool::release(MeshHandle handle) {
-  SOPHIA_ASSERT(handle.isValid(), "invalid MeshHandle");
-  SOPHIA_ASSERT(handle.index < slots.size(),
-                "MeshHandle index out of range:", handle.index);
-
-  Slot& slot = slots[handle.index];
-  SOPHIA_ASSERT(slot.generation == handle.generation,
-                "stale MeshHandle (generation mismatch):", handle.index);
-  SOPHIA_ASSERT(slot.mesh != nullptr,
-                "MeshHandle already released:", handle.index);
-
-  slot.mesh.reset();
-  slot.generation = (slot.generation + 1) & GENERATION_MASK;
-  freeList.push_back(handle.index);
-}
-
-}  // namespace sophia

engine/src/resources/pools/mesh_pool.hpp

@@ -1,35 +0,0 @@
-#pragma once
-
-#include <memory>
-#include <vector>
-
-#include "device.hpp"
-#include "mesh.hpp"
-
-namespace sophia {
-
-class MeshPool {
- public:
-  explicit MeshPool(Device& device);
-  ~MeshPool();
-
-  MeshPool(const MeshPool&) = delete;
-  MeshPool& operator=(const MeshPool&) = delete;
-
-  MeshHandle create(const Mesh::Builder& builder);
-  const Mesh& get(MeshHandle handle) const;
-  void release(MeshHandle handle);
-
- private:
-  struct Slot {
-    std::unique_ptr<Mesh> mesh;
-    u32 generation = 0;
-  };
-
-  Device& device;
-
-  std::vector<Slot> slots;
-  std::vector<u32> freeList;
-};
-
-}  // namespace sophia

engine/src/resources/pools/pool.hpp

@@ -0,0 +1,90 @@
+#pragma once
+
+#include <memory>
+#include <sophia/types.hpp>
+#include <sophia/util/assert.hpp>
+#include <utility>
+#include <vector>
+
+namespace sophia {
+
+template <typename T, typename HandleT>
+class Pool {
+ public:
+  explicit Pool(const char* name) : name{name} {}
+
+  Pool(const Pool&) = delete;
+  Pool& operator=(const Pool&) = delete;
+
+  template <typename... Args>
+  HandleT create(Args&&... args) {
+    auto item = std::make_unique<T>(std::forward<Args>(args)...);
+
+    if (!freeList.empty()) {
+      u32 index = freeList.back();
+      freeList.pop_back();
+      slots[index].item = std::move(item);
+      return HandleT{index, slots[index].generation};
+    }
+
+    slots.push_back(Slot{std::move(item), 0});
+    return HandleT{static_cast<u32>(slots.size() - 1), 0};
+  }
+
+  T& get(HandleT handle) {
+    return const_cast<T&>(std::as_const(*this).get(handle));
+  }
+
+  const T& get(HandleT handle) const { return *validate(handle).item; }
+
+  void release(HandleT handle) {
+    validate(handle);
+
+    Slot& slot = slots[handle.index];
+    slot.item.reset();
+    slot.generation = (slot.generation + 1) & GENERATION_MASK;
+    freeList.push_back(handle.index);
+  }
+
+  bool isAlive(HandleT handle) const {
+    return handle.isValid() && handle.index < slots.size() &&
+           slots[handle.index].generation == handle.generation &&
+           slots[handle.index].item != nullptr;
+  }
+
+  template <typename Fn>
+  void forEach(Fn&& fn) {
+    for (Slot& slot : slots) {
+      if (slot.item) {
+        fn(*slot.item);
+      }
+    }
+  }
+
+ private:
+  static constexpr u32 GENERATION_MASK = (1u << 12) - 1;
+
+  struct Slot {
+    std::unique_ptr<T> item;
+    u32 generation = 0;
+  };
+
+  const Slot& validate(HandleT handle) const {
+    SOPHIA_ASSERT(handle.isValid(), "invalid handle:", name);
+    SOPHIA_ASSERT(handle.index < slots.size(), name,
+                  "handle index out of range:", handle.index);
+
+    const Slot& slot = slots[handle.index];
+    SOPHIA_ASSERT(slot.generation == handle.generation, "stale", name,
+                  "handle (generation mismatch):", handle.index);
+    SOPHIA_ASSERT(slot.item != nullptr, name,
+                  "handle refers to a released item:", handle.index);
+    return slot;
+  }
+
+  const char* name;
+  std::vector<Slot> slots;
+  std::vector<u32> freeList;
+};
+
+}  // namespace sophia

engine/src/resources/pools/render_target_pool.cpp

@@ -1,81 +1,22 @@
 #include "resources/pools/render_target_pool.hpp"
 
-#include <sophia/util/assert.hpp>
-#include <utility>
-
 namespace sophia {
 
-namespace {
-constexpr u32 GENERATION_MASK = (1u << 12) - 1;
-}  // namespace
-
 RenderTargetPool::RenderTargetPool(Device& device, vk::Format format)
     : device{device}, format{format} {}
 
-RenderTargetPool::~RenderTargetPool() = default;
-
 RenderTargetHandle RenderTargetPool::create(u32 width, u32 height) {
-  auto target = std::make_unique<RenderTarget>(device, format, width, height);
-
-  if (!freeList.empty()) {
-    u32 index = freeList.back();
-    freeList.pop_back();
-    slots[index].target = std::move(target);
-    return RenderTargetHandle{index, slots[index].generation};
-  }
-
-  slots.push_back(Slot{std::move(target), 0});
-  return RenderTargetHandle{static_cast<u32>(slots.size() - 1), 0};
-}
-
-const RenderTargetPool::Slot& RenderTargetPool::validate(
-    RenderTargetHandle handle) const {
-  SOPHIA_ASSERT(handle.isValid(), "invalid RenderTargetHandle");
-  SOPHIA_ASSERT(handle.index < slots.size(),
-                "RenderTargetHandle index out of range:", handle.index);
-
-  const Slot& slot = slots[handle.index];
-  SOPHIA_ASSERT(
-      slot.generation == handle.generation,
-      "stale RenderTargetHandle (generation mismatch):", handle.index);
-  SOPHIA_ASSERT(
-      slot.target != nullptr,
-      "RenderTargetHandle refers to a released target:", handle.index);
-  return slot;
-}
-
-RenderTarget& RenderTargetPool::get(RenderTargetHandle handle) {
-  return const_cast<RenderTarget&>(std::as_const(*this).get(handle));
-}
-
-const RenderTarget& RenderTargetPool::get(RenderTargetHandle handle) const {
-  return *validate(handle).target;
+  return pool.create(device, format, width, height);
 }
 
 void RenderTargetPool::release(RenderTargetHandle handle) {
-  validate(handle);
-
-  // Earlier frames may still be rendering into or sampling the target.
+  SOPHIA_ASSERT(pool.isAlive(handle), "invalid RenderTargetHandle");
   device.waitIdle();
-
-  Slot& slot = slots[handle.index];
-  slot.target.reset();
-  slot.generation = (slot.generation + 1) & GENERATION_MASK;
-  freeList.push_back(handle.index);
-}
-
-bool RenderTargetPool::isAlive(RenderTargetHandle handle) const {
-  return handle.isValid() && handle.index < slots.size() &&
-         slots[handle.index].generation == handle.generation &&
-         slots[handle.index].target != nullptr;
+  pool.release(handle);
 }
 
 void RenderTargetPool::applyPendingResizes() {
-  for (Slot& slot : slots) {
-    if (slot.target) {
-      slot.target->applyPendingResize();
-    }
-  }
+  pool.forEach([](RenderTarget& target) { target.applyPendingResize(); });
 }
 
 }  // namespace sophia

engine/src/resources/pools/render_target_pool.hpp

@@ -1,44 +1,36 @@
 #pragma once
 
-#include <memory>
 #include <sophia/handles.hpp>
-#include <vector>
 
 #include "device.hpp"
 #include "render_target.hpp"
+#include "resources/pools/pool.hpp"
 
 namespace sophia {
 
 class RenderTargetPool {
  public:
   RenderTargetPool(Device& device, vk::Format format);
-  ~RenderTargetPool();
 
   RenderTargetPool(const RenderTargetPool&) = delete;
   RenderTargetPool& operator=(const RenderTargetPool&) = delete;
 
   RenderTargetHandle create(u32 width, u32 height);
-  RenderTarget& get(RenderTargetHandle handle);
-  const RenderTarget& get(RenderTargetHandle handle) const;
+  RenderTarget& get(RenderTargetHandle handle) { return pool.get(handle); }
+  const RenderTarget& get(RenderTargetHandle handle) const {
+    return pool.get(handle);
+  }
   void release(RenderTargetHandle handle);
 
-  bool isAlive(RenderTargetHandle handle) const;
+  bool isAlive(RenderTargetHandle handle) const { return pool.isAlive(handle); }
 
   void applyPendingResizes();
 
  private:
-  struct Slot {
-    std::unique_ptr<RenderTarget> target;
-    u32 generation = 0;
-  };
-
-  const Slot& validate(RenderTargetHandle handle) const;
-
   Device& device;
   vk::Format format;
 
-  std::vector<Slot> slots;
-  std::vector<u32> freeList;
+  Pool<RenderTarget, RenderTargetHandle> pool{"RenderTarget"};
 };
 
 }  // namespace sophia

engine/src/resources/resource_registry.cpp

@@ -1,104 +0,0 @@
-#include <sophia/resource_registry.hpp>
-#include <sophia/util/assert.hpp>
-
-#include "mesh.hpp"
-#include "pools/mesh_pool.hpp"
-#include "pools/render_target_pool.hpp"
-#include "render_target.hpp"
-
-namespace sophia {
-
-class ResourceRegistry::Impl {
- public:
-  Impl(Device& device, vk::Format renderTargetFormat)
-      : meshPool{device}, renderTargetPool{device, renderTargetFormat} {}
-
-  MeshPool meshPool;
-  RenderTargetPool renderTargetPool;
-  // TexturePool texturePool;
-  // MaterialPool materialPool;
-};
-
-ResourceRegistry::ResourceRegistry(Device& device, u32 renderTargetFormat)
-    : impl{std::make_unique<Impl>(
-          device, static_cast<vk::Format>(renderTargetFormat))} {}
-
-ResourceRegistry::~ResourceRegistry() = default;
-
-template <>
-MeshHandle ResourceRegistry::load<Mesh>(const std::string& path) {
-  (void)path;
-  SOPHIA_ASSERT(false,
-                "Mesh::load(path) is not implemented yet - no model file "
-                "format is supported; build one via Mesh::Builder for now");
-  return MeshHandle{};
-}
-
-template <typename T>
-typename ResourceTraits<T>::Handle load(const std::string&) {
-  static_assert(sizeof(T) == 0,
-                "load<T> is not implemented for this resource type");
-}
-
-template <>
-void ResourceRegistry::release<Mesh>(MeshHandle handle) {
-  impl->meshPool.release(handle);
-}
-
-template <>
-void ResourceRegistry::release<RenderTarget>(RenderTargetHandle handle) {
-  impl->renderTargetPool.release(handle);
-}
-
-template <>
-const Mesh& ResourceRegistry::get<Mesh>(MeshHandle handle) const {
-  return impl->meshPool.get(handle);
-}
-
-MeshHandle ResourceRegistry::createResource(std::type_identity<Mesh>,
-                                            std::vector<CanvasVertex> vertices,
-                                            std::vector<u32> indices) {
-  Mesh::Builder builder{};
-  builder.vertices.reserve(vertices.size());
-  for (const CanvasVertex& vertex : vertices) {
-    builder.vertices.push_back({vertex.position, vertex.color});
-  }
-  builder.indices = std::move(indices);
-
-  return impl->meshPool.create(builder);
-}
-
-RenderTargetHandle ResourceRegistry::createResource(
-    std::type_identity<RenderTarget>, u32 width, u32 height) {
-  return impl->renderTargetPool.create(width, height);
-}
-
-void ResourceRegistry::requestResize(RenderTargetHandle handle, u32 width,
-                                     u32 height) {
-  impl->renderTargetPool.get(handle).requestResize(width, height);
-}
-
-glm::vec2 ResourceRegistry::getExtent(RenderTargetHandle handle) const {
-  vk::Extent2D extent =
-      std::as_const(impl->renderTargetPool).get(handle).getExtent();
-  return {static_cast<float>(extent.width), static_cast<float>(extent.height)};
-}
-
-bool ResourceRegistry::isAlive(RenderTargetHandle handle) const {
-  return impl->renderTargetPool.isAlive(handle);
-}
-
-RenderTarget& ResourceRegistry::getRenderTarget(RenderTargetHandle handle) {
-  return impl->renderTargetPool.get(handle);
-}
-
-const RenderTarget& ResourceRegistry::getRenderTarget(
-    RenderTargetHandle handle) const {
-  return std::as_const(impl->renderTargetPool).get(handle);
-}
-
-void ResourceRegistry::applyPendingResizes() {
-  impl->renderTargetPool.applyPendingResizes();
-}
-
-}  // namespace sophia

engine/src/resources/resource_registry.hpp

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <sophia/handles.hpp>
+
+#include "device.hpp"
+#include "mesh.hpp"
+#include "resources/pools/pool.hpp"
+#include "resources/pools/render_target_pool.hpp"
+#include "scene.hpp"
+
+namespace sophia {
+
+class ResourceRegistry {
+ public:
+  ResourceRegistry(const ResourceRegistry&) = delete;
+  ResourceRegistry& operator=(const ResourceRegistry&) = delete;
+
+  ResourceRegistry(Device& device, vk::Format renderTargetFormat)
+      : device{device}, renderTargetPool{device, renderTargetFormat} {}
+
+  Device& device;
+  Pool<Mesh, MeshHandle> meshPool{"Mesh"};
+  RenderTargetPool renderTargetPool;
+  Pool<Scene, SceneHandle> scenePool{"Scene"};
+  // TexturePool textures;
+  // MaterialPool materials;
+};
+
+}  // namespace sophia

engine/src/resources/resource_registry_ref.cpp

@@ -0,0 +1,72 @@
+#include <sophia/resource_registry_ref.hpp>
+#include <sophia/util/assert.hpp>
+
+#include "resources/resource_registry.hpp"
+
+namespace sophia {
+
+template <>
+MeshHandle ResourceRegistryRef::load<Mesh>(const std::string& path) {
+  (void)path;
+  SOPHIA_ASSERT(false,
+                "Mesh::load(path) is not implemented yet - no model file "
+                "format is supported; build one via Mesh::Builder for now");
+  return MeshHandle{};
+}
+
+template <>
+void ResourceRegistryRef::release<Mesh>(MeshHandle handle) {
+  registry->meshPool.release(handle);
+}
+
+template <>
+void ResourceRegistryRef::release<RenderTarget>(RenderTargetHandle handle) {
+  registry->renderTargetPool.release(handle);
+}
+
+template <>
+void ResourceRegistryRef::release<Scene>(SceneHandle handle) {
+  registry->scenePool.release(handle);
+}
+
+MeshHandle ResourceRegistryRef::createResource(
+    std::type_identity<Mesh>, std::vector<CanvasVertex> vertices,
+    std::vector<u32> indices) {
+  Mesh::Builder builder{};
+  builder.vertices.reserve(vertices.size());
+  for (const CanvasVertex& vertex : vertices) {
+    builder.vertices.push_back({vertex.position, vertex.color});
+  }
+  builder.indices = std::move(indices);
+
+  return registry->meshPool.create(registry->device, builder);
+}
+
+RenderTargetHandle ResourceRegistryRef::createResource(
+    std::type_identity<RenderTarget>, u32 width, u32 height) {
+  return registry->renderTargetPool.create(width, height);
+}
+
+SceneHandle ResourceRegistryRef::createResource(std::type_identity<Scene>) {
+  return registry->scenePool.create();
+}
+
+void ResourceRegistryRef::requestResize(RenderTargetHandle handle, u32 width,
+                                        u32 height) {
+  registry->renderTargetPool.get(handle).requestResize(width, height);
+}
+
+glm::vec2 ResourceRegistryRef::getExtent(RenderTargetHandle handle) const {
+  vk::Extent2D extent = registry->renderTargetPool.get(handle).getExtent();
+  return {static_cast<float>(extent.width), static_cast<float>(extent.height)};
+}
+
+bool ResourceRegistryRef::isAlive(RenderTargetHandle handle) const {
+  return registry->renderTargetPool.isAlive(handle);
+}
+
+bool ResourceRegistryRef::isAlive(SceneHandle handle) const {
+  return registry->scenePool.isAlive(handle);
+}
+
+}  // namespace sophia

engine/src/ui/ui.cpp

@@ -1,4 +1,3 @@
-#include <sophia/resource_registry.hpp>
 #include <sophia/ui/ui.hpp>
 #include <sophia/util/assert.hpp>