cimgui update

src-csharp/ExampleComponent.cs

@@ -14,6 +14,14 @@ public class ExampleComponent : Component
         Console.WriteLine($"C# deltaTime {deltaTime} object id {Owner.Id}");
         ImGui.Begin("C# WINDOW");
         ImGui.Text("Hello from ExampleComponent!");
+        if (ImGui.Button("create GameObject"))
+        {
+            GameObject.Create();
+        }
+        if (ImGui.Button("GC Collect"))
+        {
+            GC.Collect();
+        }
         ImGui.End();
     }
 }

src-csharp/GameObject.cs

@@ -39,8 +39,9 @@ public class GameObject
 
     static public GameObject Create()
     {
-        NativeMethods.createGameObject(out ulong id, out uint index);
+        NativeFunctions.createGameObject(out ulong id, out uint index);
         var o = new GameObject(id, index);
+        Console.WriteLine($"C# created object with id {id}, index {index}");
         return o;
     }
 
@@ -49,23 +50,29 @@ public class GameObject
         if(_isDestroyed)
             return;
 
-        _isDestroyed = NativeMethods.destroyGameObject(_index);
+        _isDestroyed = NativeFunctions.freeGameObject(_index);
         if(!_isDestroyed)
             throw new Exception($"Can't destroy GameObject({_id})");
     }
 
+    ~GameObject()
+    {
+        // destroys object native part when managed part is garbage-collected
+        Destroy();
+    }
+
     /// <param name="t">type derived from Component</param>
     /// <returns>true if new component instance was created, false if component of the same tipe is already added to GameObject</returns>
     /// <exception cref="Exception"></exception>
     public bool TryCreateComponent(Type t)
     {
-        if(!t.IsSubclassOf(typeof(Component)))
+        if (!t.IsSubclassOf(typeof(Component)))
             throw new Exception($"type {t.FullName} is not a derived class of {typeof(Component).FullName}");
 
-        if(Components.ContainsKey(t))
+        if (Components.ContainsKey(t))
             return false;
-        
-        Component component = (Component?)Activator.CreateInstance(t, this) 
+
+        Component component = (Component?)Activator.CreateInstance(t, this)
             ?? throw new Exception($"can't create instance of class {t.FullName}");
         Components.Add(t, component);
         return true;
@@ -78,7 +85,9 @@ public class GameObject
     
     private void InvokeUpdate(double deltaTime)
     {
-        foreach(var p in Components)
+        Console.WriteLine("C# InvokeUpdate");
+        Console.WriteLine($"id {_id}, index {_index}, destroyed {_isDestroyed}");
+        foreach (var p in Components)
         {
             p.Value.Update(deltaTime);
         }

src-csharp/NativeFunctions.cs

@@ -0,0 +1,12 @@
+using System.Runtime.CompilerServices;
+
+namespace Ougge;
+
+internal static class NativeFunctions
+{
+    [MethodImpl(MethodImplOptions.InternalCall)]
+    internal extern static void createGameObject(out ulong id, out uint index);
+
+    [MethodImpl(MethodImplOptions.InternalCall)]
+    internal extern static bool freeGameObject(uint index);   
+}

src-csharp/NativeMethods.cs

@@ -1,13 +0,0 @@
-using System;
-using System.Runtime.InteropServices;
-
-namespace Ougge;
-
-internal static class NativeMethods
-{
-    [DllImport("__Internal")]
-    internal extern static bool destroyGameObject(uint index);
-    
-    [DllImport("__Internal")]
-    internal extern static void createGameObject(out ulong id, out uint index);
-}

src/Engine.cpp

@@ -1,26 +1,22 @@
 #include "Engine.hpp"
-#include "gui/gui.hpp"
+#include "common/UsefulException.hpp"
+#include "common/ougge_format.hpp"
+#include "common/time.hpp"
+#include <SDL2/SDL.h>
+#include <iostream>
 
 namespace ougge {
 
-Engine::Engine()
-    : gameObjectPool(GAMEOBJECTPOOL_SIZE), textures(&resourceManager)
+IEngineModule::IEngineModule(Engine& engine)
+    : engine(engine)
+{}
+
+void IEngineModule::beginFrame() {}
+void IEngineModule::endFrame() {}
+
+
+void Engine::startLoop()
 {
-}
-
-void Engine::init(){
-    engineManagedAssembly = mono.loadAssembly("Ougge.dll");
-    gameObjectClass = engineManagedAssembly->getClass("Ougge", "GameObject");
-    gameObjectCtor = Mono::Method<void(u64, u32)>(gameObjectClass, ".ctor");
-    gameObjectInvokeUpdate = Mono::Method<void(f64)>(gameObjectClass, "InvokeUpdate");
-    gameObjectTryCreateComponent = Mono::Method<Mono::Bool(Mono::String)>(gameObjectClass, "TryCreateComponent_internal");
-}
-
-void Engine::openMainWindow(const std::string& window_title){
-    mainWindow.open(window_title, resourceManager);
-}
-
-void Engine::startLoop(){
     if(loop_running)
         throw UsefulException("loop is running already");
     
@@ -28,87 +24,79 @@ void Engine::startLoop(){
     loop_running=true;
     // main loop
     while(loop_running){
-        mainWindow.pollEvents(&loop_running);
-        if(!loop_running)
-            break;
-        
         nsec_t update_time_ns = getMonotonicTimeNsec();
         if(update_time_ns < prev_update_time_ns)
             throw UsefulException("monotonic clock returned unexpected value");
         f64 delta_time_s = (f64)(update_time_ns - prev_update_time_ns) / 1e9;
         prev_update_time_ns = update_time_ns;
-        
-        tryDrawFrame(delta_time_s);
+        deltaTime = delta_time_s;
+
+        tryDrawFrame();
         
         nsec_t after_update_time_ns = getMonotonicTimeNsec();
-        nsec_t frame_delay_ns = (nsec_t)1e9 / mainWindow.fps_max - (after_update_time_ns - update_time_ns);
+        nsec_t frame_delay_ns = (nsec_t)1e9 / fps_max - (after_update_time_ns - update_time_ns);
         if(frame_delay_ns > 0){
             SDL_Delay(frame_delay_ns / 1e6);
         }
     }
-
-    mainWindow.close();
 }
 
 void Engine::stopLoop(){
     loop_running = false;
 }
 
-void Engine::tryDrawFrame(f64 deltaTime){
-    static std::string error_message;
-    static bool draw_error_window = false;
-    try {
-        mainWindow.beginFrame();
-        
-        if(draw_error_window)
-            gui::drawErrorWindow(error_message, &draw_error_window);
-        else {
-            updateGameObjects(deltaTime);
-            if(!updateCallback.isNull())
-                updateCallback(deltaTime);
+void Engine::handleModuleError(IEngineModule& module, const char* type, const char* method, const char* error){
+    std::string error_message = ougge_format(
+        "Catched %s at %s.%s(): %s",
+        type, module.getName().c_str(), method, error);
+    std::cerr<<error_message<<std::endl;
+    error_messages.push_back(error_message);
+}
+
+void Engine::tryDrawFrame(){
+    auto it = modules.begin();
+    while(it != modules.end())
+    {
+        IEngineModule& module = **it;
+        it++;
+        try {
+            module.beginFrame();
+        }
+        catch(const std::exception& e){
+            handleModuleError(module, "exception", "beginFrame", e.what());
+        }
+        catch(const char* cstr){
+            handleModuleError(module, "error message (const char*)", "beginFrame", cstr);
+        }
+        catch(const std::string& str){
+            handleModuleError(module, "error message (std::string)", "beginFrame", str.c_str());
+        }
+        catch(...){
+            handleModuleError(module, "unknown", "beginFrame", "unknown");
         }
-        mainWindow.endFrame();
     }
-    catch(const std::exception& e){
-        error_message = "Catched exception: " + std::string(e.what());
-        draw_error_window = true;
-        std::cerr<<error_message<<std::endl;
-    }
-    catch(const char* cstr){
-        error_message = "Catched error message (const char*): " + std::string(cstr);
-        draw_error_window = true;
-        std::cerr<<error_message<<std::endl;
-    }
-    catch(const std::string& str){
-        error_message = "Catched error message (std::string): " + str;
-        draw_error_window = true;
-        std::cerr<<error_message<<std::endl;
-    }
-    catch(...){
-        error_message = "Catched unknown error";
-        draw_error_window = true;
-        std::cerr<<error_message<<std::endl;
+
+    it = modules.end();
+    while(it != modules.begin())
+    {
+        it--;
+        IEngineModule& module = **it;
+        try {
+            module.endFrame();
+        }
+        catch(const std::exception& e){
+            handleModuleError(module, "exception", "endFrame", e.what());
+        }
+        catch(const char* cstr){
+            handleModuleError(module, "error message (const char*)", "endFrame", cstr);
+        }
+        catch(const std::string& str){
+            handleModuleError(module, "error message (std::string)", "endFrame", str.c_str());
+        }
+        catch(...){
+            handleModuleError(module, "unknown", "endFrame", "unknown");
+        }
     }
 }
 
-
-void Engine::updateGameObjects(f64 deltaTime){
-    for(auto pair : gameObjectPool){
-        gameObjectInvokeUpdate(pair.second.getObjectHandle().getObject(), deltaTime);
-    }
-}
-
-game::GameObject& Engine::createGameObject(){
-    auto pair = gameObjectPool.emplace(game::GameObject(mono.createObject(gameObjectClass)));
-    game::GameObject& obj = pair.second;
-    gameObjectCtor(obj.getObjectHandle().getObject(), ++obj_id, pair.first);
-    return obj;
-}
-
-bool Engine::tryCreateComponent(game::GameObject& obj, const std::string& componentClassName){
-    Mono::String componentClassNameManaged = mono.createString(componentClassName);
-    Mono::Bool created = gameObjectTryCreateComponent(obj.getObjectHandle().getObject(), componentClassNameManaged);
-    return created.wide_bool;
-}
-
 }

src/Engine.hpp

@@ -1,51 +1,106 @@
 #pragma once
 
-#include "common/function_shared_ptr.hpp"
-#include "mono/mono.hpp"
-#include "game/GameObjectPool.hpp"
-#include "gui/MainWindow.hpp"
-#include "resources/textures.hpp"
+#include <vector>
+#include "common/std.hpp"
+#include "common/UsefulException.hpp"
+#include "common/ougge_format.hpp"
+#include "common/type_name_demangled.hpp"
+#include <type_traits>
+#include <memory>
+#include <iostream>
 
 namespace ougge {
 
-#define GAMEOBJECTPOOL_SIZE 64*1024
+class Engine;
+
+class IEngineModule {
+public:
+    IEngineModule() = delete;
+    IEngineModule(const IEngineModule&) = delete;
+    IEngineModule& operator=(const IEngineModule&) = delete;
+    IEngineModule(IEngineModule&&) = delete;
+    IEngineModule& operator=(IEngineModule&&) = delete;
+
+    Engine& engine;
+    virtual const std::string& getName() = 0;
+
+    virtual void beginFrame();
+    virtual void endFrame();
+
+protected:
+    IEngineModule(Engine& engine);
+};
 
-using UpdateFunc_t = function_shared_ptr<void(f64)>;
 
 class Engine {
+    std::vector<std::unique_ptr<IEngineModule>> modules;
     bool loop_running = false;
 
-    game::GameObjectPool gameObjectPool;
-    u64 obj_id = 0;
-    MonoClass* gameObjectClass;
-    Mono::Method<void(u64, u32)> gameObjectCtor;
-    Mono::Method<void(f64)> gameObjectInvokeUpdate;
-    Mono::Method<Mono::Bool(Mono::String)> gameObjectTryCreateComponent;
-    
 public:
-    gui::MainWindow mainWindow;
-    UpdateFunc_t updateCallback;
+    u32 fps_max = 60;
+    f64 deltaTime;
+    std::vector<std::string> error_messages;
+    
+    Engine() = default;
+    Engine(const Engine&) = delete;
+    Engine& operator=(const Engine&) = delete;
+    Engine(Engine&&) = delete;
+    Engine& operator=(Engine&&) = delete;
 
-    Mono::RuntimeJIT mono;
-    std::shared_ptr<Mono::Assembly> engineManagedAssembly;
-
-    resources::ResourceManager resourceManager;
-    resources::CacheStorage<resources::Texture> textures;
-
-    Engine();
-    void init();
-    void openMainWindow(const std::string& window_title);
     // start game loop on the current thread
     void startLoop();
     void stopLoop();
 
-    game::GameObject& createGameObject();
-    bool tryCreateComponent(game::GameObject& obj, const std::string& componentClassName);
-    
+    //TODO: add std::enable_if
+    template<typename ModuleT, typename... ConstructorArgsT>
+    ModuleT& createModule(ConstructorArgsT&&... args){
+        static_assert(std::is_base_of<IEngineModule, ModuleT>::value);
+
+        auto& module_type_name = ougge_type_name<ModuleT>();
+        //TODO: replace with some logger call
+        std::cout<<"Initializing module '"<<module_type_name<<"'"<<std::endl;
+        
+        size_t module_index;
+        bool module_exists;
+        getOrCreateModuleIndex<ModuleT>(&module_index, &module_exists);
+
+        if(module_exists){
+            throw UsefulException(ougge_format("can't create second instance of module '%s'", 
+                module_type_name.c_str()));
+        }
+
+        //TODO: std::forward(args)...
+        modules.push_back(std::make_unique<ModuleT>(*this, args...));
+        return *static_cast<ModuleT*>(modules[module_index].get());
+    }
+
+    //TODO: add std::enable_if
+    template<typename ModuleT>
+    ModuleT& getModule(){
+        static_assert(std::is_base_of<IEngineModule, ModuleT>::value);
+        
+        size_t module_index;
+        bool module_exists;
+        getOrCreateModuleIndex<ModuleT>(&module_index, &module_exists);
+        if(!module_exists){
+            auto& module_type_name = ougge_type_name<ModuleT>();
+            throw UsefulException(ougge_format("engine has no module '%s'", 
+                module_type_name.c_str()));
+        }
+        return *static_cast<ModuleT*>(modules[module_index].get());
+    } 
 
 private:
-    void tryDrawFrame(f64 deltaTime);
-    void updateGameObjects(f64 deltaTime);
-};
+    void tryDrawFrame();
+    void handleModuleError(IEngineModule& module, const char *type, const char *method, const char *error);
 
+    //TODO: add std::enable_if
+    template<typename ModuleT>
+    void getOrCreateModuleIndex(size_t* out_index, bool* out_module_exists){
+        static size_t module_index = modules.size();
+        *out_index = module_index;
+        // if module_index == modules.size(), then the module hasn't been pushed to the vector yet
+        *out_module_exists = module_index != modules.size();
+    }
+};
 }

src/common/UsefulException.hpp

@@ -15,7 +15,7 @@ class UsefulException_ : public std::exception {
 public:
     UsefulException_(const std::string& msg, const std::string& _file, const std::string& _func, int line_n);
 
-    virtual char const* what() const noexcept;
+    char const* what() const noexcept override;
 };
 
 #define useful_assert(EXPR, ERRMSG) if(!(EXPR)) throw UsefulException(ERRMSG);

src/common/function_shared_ptr.hpp

@@ -30,13 +30,12 @@ public:
 
     bool isNull() const { return func_ptr == nullptr; }
 
-    //TODO: make inline
-
     // ReturnT is not void
     template<typename RT = ReturnT>
     std::enable_if_t<!std::is_void<RT>::value, RT>  operator()(ArgTypes... args){
         if(func_ptr == nullptr)
             throw UsefulException("function_shared_ptr is null");
+        //TODO: think about std::forward(args)...
         return func_ptr->operator()(args...);
     }
     

src/common/std.hpp

@@ -17,7 +17,6 @@ typedef double f64;
 /// anonymous pointer without specified freeMembers() func
 typedef void* Pointer;
 
-#define nameof(V) #V
 
 #ifdef _MSC_VER
     #pragma comment(lib, "mincore_downlevel.lib") // Support OS older than SDK

src/common/type_name_demangled.hpp

@@ -0,0 +1,44 @@
+// https://stackoverflow.com/a/53865723
+
+#pragma once
+#ifndef _MSC_VER
+    #include <cxxabi.h>
+#endif
+#include <memory>
+#include <string>
+#include <cstdlib>
+
+template <class T>
+std::string _ougge_type_name_demangled()
+{
+    typedef typename std::remove_reference<T>::type TR;
+    const char* type_name_mangled = typeid(TR).name();
+    std::unique_ptr<char, void(*)(void*)> own
+        (
+#ifndef _MSC_VER
+            abi::__cxa_demangle(type_name_mangled, nullptr, nullptr, nullptr),
+#else
+            nullptr,
+#endif
+            std::free
+        );
+    std::string r = own ? own.get() : type_name_mangled;
+    
+    if (std::is_const<TR>::value)
+        r += " const";
+    if (std::is_volatile<TR>::value)
+        r += " volatile";
+    if (std::is_lvalue_reference<T>::value)
+        r += "&";
+    else if (std::is_rvalue_reference<T>::value)
+        r += "&&";
+    
+    return r;
+}
+
+/// @return human-readable type name
+template <class T>
+const std::string& ougge_type_name(){
+    static std::string name = _ougge_type_name_demangled<T>();
+    return name;
+}

src/game/GameObjectPool.cpp

@@ -94,17 +94,20 @@ std::pair<u32, GameObject&> GameObjectPool::emplace(GameObject&& new_obj)
     return std::pair<u32, GameObject&>(i, r);
 }
 
-void GameObjectPool::erase(u32 index)
+bool GameObjectPool::erase(u32 index)
 {
     if(index >= size)
         throw UsefulException(ougge_format("index %i is out of size %i", index, size));
-    if(!isIndexUsed(index))
-        throw UsefulException(ougge_format("there is no object at index %i", index));
+    if(!isIndexUsed(index)){
+        // throw UsefulException(ougge_format("there is no object at index %i", index));
+        return false;
+    }
     
     buffer[index] = GameObject();
     used_indices[index/64] &= ~(u64(1)<<(index%64)); // mark index bit as unused
     if(index < first_unused_index)
         first_unused_index = index;
+    return true;
 }
 
 GameObjectPool::iterator::iterator(GameObjectPool* pool, u32 index)

src/game/GameObjectPool.hpp

@@ -45,7 +45,7 @@ public:
     ~GameObjectPool();
     GameObject& get(u32 index);
     std::pair<u32, GameObject&> emplace(GameObject&& new_obj);
-    void erase(u32 index);
+    bool erase(u32 index);
 
     #pragma region iterator class
     class iterator {

src/gui/ErrorWindow.cpp

@@ -1,11 +0,0 @@
-#include "gui.hpp"
-
-namespace ougge::gui {
-
-void drawErrorWindow(const std::string& msg, bool* draw_error_window){
-    ImGui::Begin("ERROR", draw_error_window);
-        ImGui::Text("%s", msg.c_str());
-    ImGui::End();
-}
-
-}

src/gui/gui.hpp

@@ -1,11 +0,0 @@
-#pragma once
-
-#include <SDL.h>
-#include <imgui.h>
-#include "gui_exceptions.hpp"
-
-namespace ougge::gui {
-
-void drawErrorWindow(const std::string& msg, bool* draw_error_window);
-
-}

src/main.cpp

@@ -1,49 +1,67 @@
 #define SDL_MAIN_HANDLED
 #include <iostream>
 #include <iomanip>
-#include "common/UsefulException.hpp"
-#include "common/ougge_format.hpp"
 #include "Engine.hpp"
-#include "gui/gui.hpp"
+#include "modules/MainWindowSDL2.hpp"
+#include "modules/MonoGameObjectSystem.hpp"
+#include "resources/textures.hpp"
 
 using namespace ougge;
 
-void drawTutel(Engine& engine){
-    resources::Texture* tutel = engine.textures.tryGetOrCreate("tutel.png", engine.mainWindow.sdl_renderer);
-    if(tutel == nullptr){
-        throw new UsefulException("couldn't find resource 'tutel.png'");
+class TutelModule : public IEngineModule {
+    resources::CacheStorage<resources::Texture> textures;
+public:
+    TutelModule(Engine& engine, resources::ResourceManager& resourceManager) :
+        IEngineModule(engine),
+        textures(&resourceManager)
+    {
+        //TODO: add something like `assert(requireModule(MainWindow))`
     }
-    resources::SDL_RenderCopyExF_Params params;
-    params.target_section = SDL_FRectConstruct(100, 100, 400, 400);
-    static i32 si = 1;
-    params.rotation_angle = M_PI_4 * (si++ / engine.mainWindow.fps_max);
-    tutel->render(params);
+
+    const std::string& getName() override {
+        return ougge_type_name<TutelModule>();
+    }
+
+    void beginFrame() override {
+        auto& mainWindow = engine.getModule<modules::MainWindowSDL2>();
+        resources::Texture* tutel = textures.tryGetOrCreate("tutel.png", mainWindow.sdl_renderer);
+        if(tutel == nullptr){
+            throw new UsefulException("couldn't find resource 'tutel.png'");
+        }
+        resources::SDL_RenderCopyExF_Params params;
+        params.target_section = SDL_FRectConstruct(100, 100, 400, 400);
+        static i32 si = 1;
+        params.rotation_angle = M_PI_4 * (si++ / engine.fps_max);
+        tutel->render(params);
+    }
+
+};
+
+void createExampleObject(Engine& engine){
+    std::cout<<"creating ExampleObject"<<std::endl;
+    auto& monoSystem = engine.getModule<modules::MonoGameObjectSystem>();
+    game::GameObject& exampleObj = monoSystem.createAndConstructGameObject();
+    std::string componentClassName = "Ougge.ExampleComponent";
+    if(!monoSystem.tryCreateComponent(exampleObj, componentClassName))
+        throw UsefulException(ougge_format("couldn't create component '%s'", componentClassName.c_str()));
 }
 
 int main(int argc, const char** argv){
     try {
-        std::cout<<"initialized resource loader"<<std::endl;
-        
+        std::cout<<"Initializing Engine"<<std::endl;
         Engine engine;
-        std::cout<<"initialized mono jit runtime"<<std::endl;
-        engine.init();
-        std::cout<<"initialized game engine"<<std::endl;
+
+        std::cout<<"Initializing ResourceManager"<<std::endl;
+        resources::ResourceManager resourceManager;
+
+        engine.createModule<modules::MainWindowSDL2>("ougge", resourceManager);
+        engine.createModule<modules::MonoGameObjectSystem>(64*1024);
+        createExampleObject(engine);
+        engine.createModule<TutelModule>(resourceManager);
         
-        game::GameObject& exampleObj = engine.createGameObject();
-        std::string componentClassName = "Ougge.ExampleComponent";
-        if(!engine.tryCreateComponent(exampleObj, componentClassName))
-            throw UsefulException(ougge_format("couldn't create component '%s'", componentClassName.c_str()));
-        
-        std::cout<<"created ExampleObject"<<std::endl;
-        
-        engine.updateCallback = [&engine](f64 deltaTime) -> void {
-            drawTutel(engine);
-        };
-        
-        engine.openMainWindow("ougge");
-        std::cout<<"created sdl window"<<std::endl;
+        std::cout<<"main loop start"<<std::endl;
         engine.startLoop();
-        std::cout<<"sdl window has been cosed"<<std::endl;
+        std::cout<<"main loop stop"<<std::endl;
     }
     catch(const std::exception& e){
         std::cerr<<"Catched exception: "<<e.what()<<std::endl;

src/modules/MainWindowSDL2.cpp

@@ -1,14 +1,20 @@
 #include <backends/imgui_impl_sdl2.h>
 #include <backends/imgui_impl_sdlrenderer2.h>
 #include <iostream>
-#include "MainWindow.hpp"
-#include "gui_exceptions.hpp"
+#include "MainWindowSDL2.hpp"
+#include "../gui/gui_exceptions.hpp"
 #include "../common/ougge_format.hpp"
 #include "../common/math.hpp"
 
-namespace ougge::gui {
+using namespace ougge::gui;
 
-f32 MainWindow::getDPI(){
+namespace ougge::modules {
+
+const std::string& MainWindowSDL2::getName() {
+    return ougge_type_name<MainWindowSDL2>();
+}
+
+f32 MainWindowSDL2::getDPI(){
     i32 w=0, h=0;
     SDL_GetRendererOutputSize(sdl_renderer, &w, &h);
     i32 sim_w=0, sim_h=0;
@@ -19,7 +25,11 @@ f32 MainWindow::getDPI(){
     return dpi;
 }
 
-void MainWindow::open(const std::string& window_title, resources::ResourceManager& resourceManager){
+MainWindowSDL2::MainWindowSDL2(Engine& engine,
+        const std::string& window_title,
+        resources::ResourceManager& resourceManager)
+    : IEngineModule(engine)
+{
     SDL_TRY(SDL_Init(SDL_INIT_EVERYTHING));
     SDL_version v;
     SDL_GetVersion(&v);
@@ -78,7 +88,7 @@ void MainWindow::open(const std::string& window_title, resources::ResourceManage
     io.FontDefault = resources::ImFont_LoadFromResource(font_res, default_font_size, dpi);
 }
 
-void MainWindow::close(){
+MainWindowSDL2::~MainWindowSDL2(){
     ImGui_ImplSDLRenderer2_Shutdown();
     ImGui_ImplSDL2_Shutdown();
     ImGui::DestroyContext();
@@ -87,20 +97,22 @@ void MainWindow::close(){
     SDL_Quit();
 }
 
-void MainWindow::pollEvents(bool* loopRunning){
+void MainWindowSDL2::pollEvents(){
     SDL_Event event;
     while (SDL_PollEvent(&event)) {
         ImGui_ImplSDL2_ProcessEvent(&event);
         switch(event.type){
             case SDL_QUIT: {
-                *loopRunning = false;
+                //TODO: log SDL_QUIT event
+                engine.stopLoop();
                 break;
             }
             case SDL_WINDOWEVENT: {
                 if(event.window.event == SDL_WINDOWEVENT_CLOSE 
                     && event.window.windowID == SDL_GetWindowID(sdl_window))
                 {
-                    *loopRunning = false;
+                    //TODO: log SDL_WINDOWEVENT event
+                    engine.stopLoop();
                 }
                 break;
             }
@@ -108,8 +120,10 @@ void MainWindow::pollEvents(bool* loopRunning){
     }
 }
 
+void MainWindowSDL2::beginFrame(){
+    // process events happend since previous frame
+    pollEvents();
 
-void MainWindow::beginFrame(){
     // Start the Dear ImGui frame
     ImGui_ImplSDLRenderer2_NewFrame();
     ImGui_ImplSDL2_NewFrame();
@@ -126,16 +140,17 @@ void MainWindow::beginFrame(){
 
     draw_bg_window();
     draw_debug_window();
+    drawErrorWindow();
 }
 
-void MainWindow::endFrame(){
+void MainWindowSDL2::endFrame(){
     ImGui::Render();
     ImGui_ImplSDLRenderer2_RenderDrawData(ImGui::GetDrawData(), sdl_renderer);
     // Swap buffers
     SDL_RenderPresent(sdl_renderer);
 }
 
-void MainWindow::draw_bg_window(){
+void MainWindowSDL2::draw_bg_window(){
     const ImGuiDockNodeFlags dockspace_flags =
             ImGuiDockNodeFlags_PassthruCentralNode;
     const ImGuiWindowFlags window_flags =
@@ -199,11 +214,11 @@ void MainWindow::draw_bg_window(){
     ImGui::End();
 }
 
-void MainWindow::draw_debug_window(){
+void MainWindowSDL2::draw_debug_window(){
     ImGuiIO& io = ImGui::GetIO();
     if(ImGui::Begin("Debug Options", &show_debug_window)){
         ImGui::ColorEdit3("clear_color", (float*)&clear_color);
-        ImGui::InputInt("fps_max", &fps_max);
+        ImGui::InputInt("fps_max", (int*)&engine.fps_max);
         ImGui::Text("Application average %.3f ms/frame (%.2f FPS)", 1000.0f / io.Framerate, io.Framerate);
         ImGui::Checkbox("Demo Window", &show_demo_window);
         ImGui::Checkbox("Metrics/Debug Window", &show_metrics_window);
@@ -217,4 +232,16 @@ void MainWindow::draw_debug_window(){
         ImGui::ShowMetricsWindow(&show_metrics_window);
 }
 
+void MainWindowSDL2::drawErrorWindow(){
+    if(engine.error_messages.size() < 1)
+        return;
+    ImGui::Begin("ERRORS");
+        if(ImGui::Button("Clear"))
+            engine.error_messages.clear();
+        for(auto& msg : engine.error_messages){
+            ImGui::TextWrapped("%s", msg.c_str());
+        }
+    ImGui::End();
+}
+
 }

src/modules/MainWindowSDL2.hpp

@@ -2,23 +2,23 @@
 
 #include <SDL.h>
 #include <imgui.h>
+#include <vector>
 #include "../common/std.hpp"
-#include "../common/time.hpp"
 #include "../resources/resources.hpp"
 #include "../resources/fonts.hpp"
+#include "../Engine.hpp"
+
+namespace ougge::modules {
 
 /// converts hex color to float vector
 #define RGBAHexToF(R8,G8,B8,A8) ImVec4(((u8)35)/255.0f, ((u8)35)/255.0f, ((u8)50)/255.0f, ((u8)255)/255.0f)
 /// converts float vector to hex color
 #define RGBAFToHex(VEC4) {(u8)(VEC4.x*255), (u8)(VEC4.y*255), (u8)(VEC4.z*255), (u8)(VEC4.w*255)}
 
-namespace ougge::gui {
-
 #define default_font_path "fonts/DroidSans.ttf"
 
-class MainWindow {
+class MainWindowSDL2 : public IEngineModule {
 public:
-    i32 fps_max = 60;
     f32 default_font_size = 14.0f;
     ImVec4 clear_color = RGBAHexToF(35,35,50,255);
     SDL_Window* sdl_window = nullptr;
@@ -30,18 +30,20 @@ private:
     bool show_metrics_window = false;
 
 public:
-    void open(const std::string& window_title, resources::ResourceManager& resourceManager);
-    void close();
+    MainWindowSDL2(Engine& engine, const std::string& window_title,
+        resources::ResourceManager& resourceManager);
+    ~MainWindowSDL2();
 
-    /// process io events happened since previous frame
-    void pollEvents(bool* loopRunning);
-    void beginFrame();
-    void endFrame();
+    const std::string& getName() override;
+    void beginFrame() override;
+    void endFrame() override;
 
     f32 getDPI();
 private:
+    void pollEvents();
     void draw_debug_window();
     void draw_bg_window();
+    void drawErrorWindow();
 };
 
 }

src/modules/MonoGameObjectSystem.cpp

@@ -0,0 +1,76 @@
+#include "MonoGameObjectSystem.hpp"
+
+namespace ougge::modules {
+
+const std::string& MonoGameObjectSystem::getName() {
+    return ougge_type_name<MonoGameObjectSystem>();
+}
+
+MonoGameObjectSystem::MonoGameObjectSystem(Engine& engine, u32 max_game_objects) :
+    IEngineModule(engine), 
+    gameObjectPool(max_game_objects)
+{
+    engineManagedAssembly = mono.loadAssembly("Ougge.dll");
+    gameObjectClass = engineManagedAssembly->getClass("Ougge", "GameObject");
+    gameObjectCtor = Mono::Method<void(u64, u32)>(gameObjectClass, ".ctor");
+    gameObjectInvokeUpdate = Mono::Method<void(f64)>(gameObjectClass, "InvokeUpdate");
+    gameObjectTryCreateComponent = Mono::Method<Mono::Bool(Mono::String)>(gameObjectClass, "TryCreateComponent_internal");
+    registerNativeCallbacks();
+}
+
+// sets implementations for extern functions from src-csharp/NativeFunctions.cs
+void MonoGameObjectSystem::registerNativeCallbacks(){
+    static MonoGameObjectSystem* this_static = this;
+    if(this_static != this)
+        throw new UsefulException("creation of more than one instance of MonoGameObjectSystem is not allowed");
+
+    auto createGameObject_callback = static_cast<void(*)(u64*, u32*)> (
+        [](u64* id_out, u32* index_out) -> void {
+            std::cout<<"createGameObject_callback"<<std::endl;
+            this_static->createGameObjectInPool(id_out, index_out);
+        }
+    );
+    mono_add_internal_call("Ougge.NativeFunctions::createGameObject", (void*)createGameObject_callback);
+    
+    auto freeGameObject_callback = static_cast<bool(*)(u32)>(
+        [](u32 index) -> bool {
+            std::cout<<"freeGameObject_callback"<<std::endl;
+            return this_static->gameObjectPool.erase(index);
+        }
+    );
+    mono_add_internal_call("Ougge.NativeFunctions::freeGameObject", (void*)freeGameObject_callback);
+}
+
+void MonoGameObjectSystem::beginFrame(){
+    for(auto pair : gameObjectPool){
+
+        auto obj = pair.second.getObjectHandle().getObject();
+        std::cout<<"updating obj: "<<obj<<std::endl;
+        gameObjectInvokeUpdate(obj, engine.deltaTime);
+    }
+}
+
+// is used in NativeFunctions.cs
+game::GameObject& MonoGameObjectSystem::createGameObjectInPool(u64* id_out, u32* index_out){
+    auto pair = gameObjectPool.emplace(game::GameObject(mono.createObject(gameObjectClass)));
+    *id_out = ++obj_id;
+    *index_out = pair.first;
+    game::GameObject& obj = pair.second;
+    return obj;
+}
+
+game::GameObject& MonoGameObjectSystem::createAndConstructGameObject(){
+    u64 obj_id;
+    u32 obj_index;
+    game::GameObject& obj = createGameObjectInPool(&obj_id, &obj_index);
+    gameObjectCtor(obj.getObjectHandle().getObject(), obj_id, obj_index);
+    return obj;
+}
+
+bool MonoGameObjectSystem::tryCreateComponent(game::GameObject& obj, const std::string& componentClassName){
+    Mono::String componentClassNameManaged = mono.createString(componentClassName);
+    Mono::Bool created = gameObjectTryCreateComponent(obj.getObjectHandle().getObject(), componentClassNameManaged);
+    return created.wide_bool;
+}
+
+}

src/modules/MonoGameObjectSystem.hpp

@@ -0,0 +1,35 @@
+#pragma once
+
+#include "../Engine.hpp"
+#include "../common/function_shared_ptr.hpp"
+#include "../mono/mono.hpp"
+#include "../game/GameObjectPool.hpp"
+
+namespace ougge::modules {
+
+class MonoGameObjectSystem : public IEngineModule {
+    Mono::RuntimeJIT mono;
+    game::GameObjectPool gameObjectPool;
+    u64 obj_id = 0;
+    MonoClass* gameObjectClass;
+    Mono::Method<void(u64, u32)> gameObjectCtor;
+    Mono::Method<void(f64)> gameObjectInvokeUpdate;
+    Mono::Method<Mono::Bool(Mono::String)> gameObjectTryCreateComponent;
+
+public:
+    std::shared_ptr<Mono::Assembly> engineManagedAssembly;
+
+    MonoGameObjectSystem(Engine& engine, u32 max_game_objects);
+    
+    const std::string& getName() override;
+    void beginFrame() override;
+    
+    game::GameObject& createAndConstructGameObject();
+    bool tryCreateComponent(game::GameObject& obj, const std::string& componentClassName);
+
+private:
+    void registerNativeCallbacks();
+    game::GameObject& createGameObjectInPool(u64* id_out, u32* index_out);
+};
+
+}

src/resources/MemorySteam.cpp

@@ -4,10 +4,10 @@ class MemoryStreamBuf : public std::streambuf {
 public:
     MemoryStreamBuf(void* p, const std::size_t n);
 
-    virtual std::istream::pos_type seekoff(
+    std::istream::pos_type seekoff(
         std::istream::off_type off,
         std::ios_base::seekdir dir,
-        std::ios_base::openmode which);
+        std::ios_base::openmode which) override;
 };
 
 MemoryStreamBuf::MemoryStreamBuf(void* _p, const std::size_t n){

src/resources/resources.hpp

@@ -23,6 +23,7 @@ public:
 
 using ResourceMap = std::unordered_map<std::string, ResourceFactory>;
 
+//TODO: rewrite ResourceManager as a module
 class ResourceManager {
     std::list<std::shared_ptr<ResourceMap>> _resourceMaps;
     static std::shared_ptr<ResourceMap> _embeddedResourcesMap;