Engine+Example: Improve entrypoint via manual singleton

example/src/game.cpp

@@ -4,17 +4,26 @@
  * SPDX-License-Identifier: MIT
  */
 
-#include "inferno.h"
-#include "inferno/entrypoint.h"
+#include "game.h"
 
-class Game : public Inferno::Application
+Game::Game()
+	: Application()
 {
-public:
-	Game() : Application({}) {}
-	~Game() {}
-};
-
-Inferno::Application& Inferno::createApplication()
-{
-	return Game::the();
+}
+
+Game::~Game()
+{
+}
+
+void Game::update()
+{
+}
+
+void Game::render()
+{
+}
+
+Inferno::Application* Inferno::createApplication(int argc, char* argv[])
+{
+	return new Game;
 }

example/src/game.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2022 Riyyi
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include "inferno.h"
+#include "inferno/entrypoint.h"
+
+class Game final : public Inferno::Application {
+public:
+	Game();
+	~Game();
+
+	void update() override;
+	void render() override;
+};
+
+Inferno::Application* Inferno::createApplication(int argc, char* argv[]);

src/inferno/application.cpp

@@ -31,8 +31,14 @@
 
 namespace Inferno {
 
-Application::Application(s)
+Application* Application::s_instance = nullptr;
+
+Application::Application()
 {
+	// Set singleton instance
+	VERIFY(!s_instance, "reinstantiation of Application");
+	s_instance = this;
+
 	// Initialize
 
 	Settings::initialize();
@@ -78,6 +84,8 @@ Application::~Application()
 	// Input::destroy();
 
 	Settings::destroy();
+
+	s_instance = nullptr;
 }
 
 int Application::run()
@@ -143,12 +151,16 @@ int Application::run()
 
 		// Update
 
+		update();
+
 		Input::update();
 		m_window->update();
 		m_scene->update(deltaTime);
 
 		// Render
 
+		render();
+
 		RenderCommand::clearColor({ 0.2f, 0.3f, 0.3f, 1.0f });
 		RenderCommand::clear();
 

src/inferno/application.h

@@ -21,11 +21,13 @@ class Window;
 class WindowCloseEvent;
 class WindowResizeEvent;
 
-class Application : public ruc::Singleton<Application> {
+class Application {
 public:
-	explicit Application(s);
 	virtual ~Application();
 
+	virtual void update() = 0;
+	virtual void render() = 0;
+
 	int run();
 
 	void onEvent(Event& e);
@@ -38,6 +40,11 @@ public:
 
 	inline Window& getWindow() const { return *m_window; }
 
+	static Application& the() { return *s_instance; }
+
+protected:
+	Application();
+
 private:
 	int m_status { 0 };
 	float m_lastFrameTime { 0.0f };
@@ -48,10 +55,12 @@ private:
 	//
 	std::shared_ptr<Font> m_font;
 	//
+
+	static Application* s_instance;
 };
 
 // To be defined in the game
-extern Application& createApplication();
+extern Application* createApplication(int argc, char* argv[]);
 
 } // namespace Inferno
 

src/inferno/entrypoint.h

@@ -16,15 +16,11 @@
 
 int main(int argc, char* argv[]) // NOLINT(misc-definitions-in-headers)
 {
-	// Suppress unused warning
-	(void)argc;
-	(void)argv;
+	auto* app = Inferno::createApplication(argc, argv);
 
-	auto& app = Inferno::createApplication();
+	int status = app->run();
 
-	int status = app.run();
-
-	app.destroy();
+	delete app;
 
 	return status;
 }