Refactor Application singleton to use protected constructor and logic_error check

.gitattributes

@@ -0,0 +1,11 @@
+# Normalize line endings
+* text=auto
+*.cpp text eol=lf
+*.hpp text eol=lf
+*.h text eol=lf
+*.cmake text eol=lf
+*.py text eol=lf
+*.yaml text eol=lf
+*.yml text eol=lf
+*.json text eol=lf
+*.md text eol=lf

CHANGELOG.md

@@ -5,6 +5,16 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+- Support for line ending normalization
+
+### Changed
+
+- Application singleton now uses protected constructor and logic_error check
+
 ## [0.6.0] - 2026-02-15
 
 - Change headers parent folder to Kappa
@@ -143,6 +153,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - CMake build system
 - Example application demonstrating framework usage
 
+[Unreleased]: https://github.com/Konstantysz/kappa-core/compare/v0.6.0...HEAD
 [0.6.0]: https://github.com/Konstantysz/kappa-core/compare/v0.5.3...v0.6.0
 [0.5.3]: https://github.com/Konstantysz/kappa-core/compare/v0.5.2...v0.5.3
 [0.5.2]: https://github.com/Konstantysz/kappa-core/compare/v0.5.1...v0.5.2

include/Kappa/Application.h

@@ -26,12 +26,6 @@ namespace Kappa
     class Application
     {
     public:
-        /**
-         * @brief Constructs an application.
-         * @param specification Application configuration
-         */
-        explicit Application(const ApplicationSpecification &specification = ApplicationSpecification());
-
         /**
          * @brief Virtual destructor for proper cleanup of derived classes.
          */
@@ -48,6 +42,12 @@ namespace Kappa
         void Stop();
 
     protected:
+        /**
+         * @brief Constructs an application.
+         * @param specification Application configuration
+         */
+        explicit Application(const ApplicationSpecification &specification = ApplicationSpecification());
+
         /**
          * @brief Adds a layer to the layer stack (default constructible version).
          * @tparam TLayer Layer type (must derive from Layer)

src/Application.cpp

@@ -1,6 +1,7 @@
 #include "Kappa/Application.h"
 
 #include <cassert>
+#include <stdexcept>
 
 #include <GLFW/glfw3.h>
 #include <glm/gtc/constants.hpp>
@@ -18,6 +19,11 @@ namespace Kappa
 
     Application::Application(const ApplicationSpecification &spec) : specification(spec)
     {
+        if (instance)
+        {
+            throw std::logic_error("Application already exists!");
+        }
+
         instance = this;
 
         glfwSetErrorCallback(GLFWErrorCallback);