feat: implement an ImGui layer

7 files changed, 84 insertions, 9 deletions

diff --git a/src/core/application.cpp b/src/core/application.cpp
index f2284cd..0698ce3 100644
--- a/src/core/application.cpp
+++ b/src/core/application.cpp
@@ -2,8 +2,8 @@
 
 #include "rendering/renderer.h"
 
-#include "states/config_state.h"
 #include "states/simulation_state.h"
+#include "states/config_state.h"
 
 #include <GLFW/glfw3.h>
 
@@ -86,12 +86,6 @@ namespace Donut
                 event.handled = true;
                 return true;
             }
-            else if (e.get_key_code() == GLFW_KEY_3)
-            {
-                m_state_manager->switch_to_state("Menu");
-                event.handled = true;
-                return true;
-            }
             
             return true;
         });
@@ -105,12 +99,13 @@ namespace Donut
         
         RendererAPI::set_api(RendererAPI::API::OpenGL);
         Renderer::init();
+        m_window->init_im_gui();
         
         Renderer::on_window_resize(1280, 720);
         RenderCommand::set_face_culling(false);
 
         m_state_manager = create_scope<StateManager>();
-        m_state_manager->register_state("Config", create_scope<ConfigState>());
+        m_state_manager->register_state("Config",     create_scope<ConfigState>());
         m_state_manager->register_state("Simulation", create_scope<SimulationState>());
         m_state_manager->switch_to_state("Config");
     }
@@ -136,5 +131,9 @@ namespace Donut
     void Application::on_render()
     {
         m_state_manager->render();
+        
+        m_window->begin_im_gui_frame();
+        m_state_manager->on_im_ui_render();
+        m_window->end_im_gui_frame();
     }
 };
diff --git a/src/core/application.h b/src/core/application.h
index 048503b..d0abac3 100644
--- a/src/core/application.h
+++ b/src/core/application.h
@@ -19,6 +19,7 @@ namespace Donut
         void close();
 
         Window& get_window()       { return *m_window;   }
+        StateManager& get_state_manager() { return *m_state_manager; }
         static Application& get() { return *s_instance; }
     private:
         void on_init();
diff --git a/src/core/state.h b/src/core/state.h
index f5d808a..f4fe9b3 100644
--- a/src/core/state.h
+++ b/src/core/state.h
@@ -13,6 +13,7 @@ namespace Donut
         virtual void on_exit()                  = 0;
         virtual void on_update(float delta_time) = 0;
         virtual void on_render()                = 0;
+        virtual void on_im_ui_render()            = 0;
         virtual void on_event(Event& event)     = 0;
     };
 };
diff --git a/src/core/state_manager.cpp b/src/core/state_manager.cpp
index 728df15..5086ddd 100644
--- a/src/core/state_manager.cpp
+++ b/src/core/state_manager.cpp
@@ -74,6 +74,12 @@ namespace Donut
             m_current_state->on_render();
     }
 
+    void StateManager::on_im_ui_render()
+    {
+        if (m_current_state)
+            m_current_state->on_im_ui_render();
+    }
+
     void StateManager::on_event(Event& event)
     {
         if (m_current_state)
diff --git a/src/core/state_manager.h b/src/core/state_manager.h
index 469c48f..584df11 100644
--- a/src/core/state_manager.h
+++ b/src/core/state_manager.h
@@ -16,6 +16,7 @@ namespace Donut
         
         void update(float delta_time);
         void render();
+        void on_im_ui_render();
         void on_event(Event& event);
         
         void register_state(const std::string& state_name, Scope<State> state);
diff --git a/src/core/window.cpp b/src/core/window.cpp
index f598357..df19b86 100644
--- a/src/core/window.cpp
+++ b/src/core/window.cpp
@@ -2,6 +2,10 @@
 
 #include <cstdint>
 
+#include <imgui.h>
+#include <imgui_impl_glfw.h>
+#include <imgui_impl_opengl3.h>
+
 namespace Donut
 {
     static bool     s_glfw_initialized = false;
@@ -66,6 +70,9 @@ namespace Donut
     void Window::shutdown()
     {
         DONUT_INFO("Shutting down window: ", m_title);
+        
+        shutdown_im_gui();
+        
         glfwDestroyWindow(m_window);
         s_glfw_window_count--;
 
@@ -102,6 +109,61 @@ namespace Donut
                          GLFW_CURSOR_NORMAL : GLFW_CURSOR_HIDDEN);
     }
 
+    void Window::init_im_gui()
+    {
+        IMGUI_CHECKVERSION();
+        ImGui::CreateContext();
+        ImGuiIO& io = ImGui::GetIO();
+        io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;
+        io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;
+        io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;
+
+        ImGui::StyleColorsDark();
+
+        ImGuiStyle& style = ImGui::GetStyle();
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            style.WindowRounding = 0.0f;
+            style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+        }
+
+        ImGui_ImplGlfw_InitForOpenGL(m_window, true);
+        ImGui_ImplOpenGL3_Init("#version 130");
+        
+        DONUT_INFO("ImGUI initialized successfully");
+    }
+
+    void Window::shutdown_im_gui()
+    {
+        ImGui_ImplOpenGL3_Shutdown();
+        ImGui_ImplGlfw_Shutdown();
+        ImGui::DestroyContext();
+        
+        DONUT_INFO("ImGUI shutdown");
+    }
+
+    void Window::begin_im_gui_frame()
+    {
+        ImGui_ImplOpenGL3_NewFrame();
+        ImGui_ImplGlfw_NewFrame();
+        ImGui::NewFrame();
+    }
+
+    void Window::end_im_gui_frame()
+    {
+        ImGui::Render();
+        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
+
+        ImGuiIO& io = ImGui::GetIO();
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            GLFWwindow* backup_current_context = glfwGetCurrentContext();
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+            glfwMakeContextCurrent(backup_current_context);
+        }
+    }
+
     void Window::glfw_error_callback(int error, const char* description)
     {
         DONUT_ERROR("GLFW Error (", error, "): ", description);
diff --git a/src/core/window.h b/src/core/window.h
index 256f708..96678f8 100644
--- a/src/core/window.h
+++ b/src/core/window.h
@@ -35,10 +35,15 @@ namespace Donut
         void set_cursor_visible(bool visible);
         bool is_cursor_locked()  const { return m_cursor_locked;  }
         bool is_cursor_visible() const { return m_cursor_visible; }
+    
+        void init_im_gui();
+        void begin_im_gui_frame();
+        void end_im_gui_frame();
     private:
         void init();
         void shutdown();
-
+        void shutdown_im_gui();
+        
         static void glfw_error_callback(int error, const char* description);
         static void glfw_window_close_callback(GLFWwindow* window);
         static void glfw_window_size_callback(GLFWwindow* window, int width, int height);