[add]: implement an ImGUI layer

7 files changed, 84 insertions, 9 deletions

diff --git a/src/Core/Application.cpp b/src/Core/Application.cpp
index a886327..9aac646 100644
--- a/src/Core/Application.cpp
+++ b/src/Core/Application.cpp
@@ -2,8 +2,8 @@
 
 #include "Rendering/Renderer.h"
 
-#include "States/ConfigState.h"
 #include "States/SimulationState.h"
+#include "States/ConfigState.h"
 
 #include <GLFW/glfw3.h>
 
@@ -86,12 +86,6 @@ namespace Donut
                 event.Handled = true;
                 return true;
             }
-            else if (e.GetKeyCode() == GLFW_KEY_3)
-            {
-                m_StateManager->SwitchToState("Menu");
-                event.Handled = true;
-                return true;
-            }
             
             return true;
         });
@@ -105,12 +99,13 @@ namespace Donut
         
         RendererAPI::SetAPI(RendererAPI::API::OpenGL);
         Renderer::Init();
+        m_Window->InitImGui();
         
         Renderer::OnWindowResize(1280, 720);
         RenderCommand::SetFaceCulling(false);
 
         m_StateManager = CreateScope<StateManager>();
-        m_StateManager->RegisterState("Config", CreateScope<ConfigState>());
+        m_StateManager->RegisterState("Config",     CreateScope<ConfigState>());
         m_StateManager->RegisterState("Simulation", CreateScope<SimulationState>());
         m_StateManager->SwitchToState("Config");
     }
@@ -136,5 +131,9 @@ namespace Donut
     void Application::OnRender()
     {
         m_StateManager->Render();
+        
+        m_Window->BeginImGuiFrame();
+        m_StateManager->OnImUIRender();
+        m_Window->EndImGuiFrame();
     }
 };
diff --git a/src/Core/Application.h b/src/Core/Application.h
index 3d0ba25..39d28bb 100644
--- a/src/Core/Application.h
+++ b/src/Core/Application.h
@@ -19,6 +19,7 @@ namespace Donut
         void Close();
 
         Window& GetWindow()       { return *m_Window;   }
+        StateManager& GetStateManager() { return *m_StateManager; }
         static Application& Get() { return *s_Instance; }
     private:
         void OnInit();
diff --git a/src/Core/State.h b/src/Core/State.h
index 2d368d7..cd1b7ee 100644
--- a/src/Core/State.h
+++ b/src/Core/State.h
@@ -13,6 +13,7 @@ namespace Donut
         virtual void OnExit()                  = 0;
         virtual void OnUpdate(float deltaTime) = 0;
         virtual void OnRender()                = 0;
+        virtual void OnImUIRender()            = 0;
         virtual void OnEvent(Event& event)     = 0;
     };
 };
\ No newline at end of file
diff --git a/src/Core/StateManager.cpp b/src/Core/StateManager.cpp
index 266bafa..e2aba02 100644
--- a/src/Core/StateManager.cpp
+++ b/src/Core/StateManager.cpp
@@ -74,6 +74,12 @@ namespace Donut
             m_CurrentState->OnRender();
     }
 
+    void StateManager::OnImUIRender()
+    {
+        if (m_CurrentState)
+            m_CurrentState->OnImUIRender();
+    }
+
     void StateManager::OnEvent(Event& event)
     {
         if (m_CurrentState)
diff --git a/src/Core/StateManager.h b/src/Core/StateManager.h
index c0b2b13..4ffc86d 100644
--- a/src/Core/StateManager.h
+++ b/src/Core/StateManager.h
@@ -16,6 +16,7 @@ namespace Donut
         
         void Update(float deltaTime);
         void Render();
+        void OnImUIRender();
         void OnEvent(Event& event);
         
         void RegisterState(const std::string& stateName, Scope<State> state);
diff --git a/src/Core/Window.cpp b/src/Core/Window.cpp
index 73bd8db..d60ebc9 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_GLFWInitialized = false;
@@ -66,6 +70,9 @@ namespace Donut
     void Window::Shutdown()
     {
         DONUT_INFO("Shutting down window: ", m_Title);
+        
+        ShutdownImGui();
+        
         glfwDestroyWindow(m_Window);
         s_GLFWWindowCount--;
 
@@ -102,6 +109,61 @@ namespace Donut
                          GLFW_CURSOR_NORMAL : GLFW_CURSOR_HIDDEN);
     }
 
+    void Window::InitImGui()
+    {
+        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::ShutdownImGui()
+    {
+        ImGui_ImplOpenGL3_Shutdown();
+        ImGui_ImplGlfw_Shutdown();
+        ImGui::DestroyContext();
+        
+        DONUT_INFO("ImGUI shutdown");
+    }
+
+    void Window::BeginImGuiFrame()
+    {
+        ImGui_ImplOpenGL3_NewFrame();
+        ImGui_ImplGlfw_NewFrame();
+        ImGui::NewFrame();
+    }
+
+    void Window::EndImGuiFrame()
+    {
+        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::GLFWErrorCallback(int error, const char* description)
     {
         DONUT_ERROR("GLFW Error (", error, "): ", description);
diff --git a/src/Core/Window.h b/src/Core/Window.h
index c598bf2..26df099 100644
--- a/src/Core/Window.h
+++ b/src/Core/Window.h
@@ -35,10 +35,15 @@ namespace Donut
         void SetCursorVisible(bool visible);
         bool IsCursorLocked()  const { return m_CursorLocked;  }
         bool IsCursorVisible() const { return m_CursorVisible; }
+    
+        void InitImGui();
+        void BeginImGuiFrame();
+        void EndImGuiFrame();
     private:
         void Init();
         void Shutdown();
-
+        void ShutdownImGui();
+        
         static void GLFWErrorCallback(int error, const char* description);
         static void GLFWWindowCloseCallback(GLFWwindow* window);
         static void GLFWWindowSizeCallback(GLFWwindow* window, int width, int height);