text: // dear imgui: standalone example application for DirectX 12
  // If you are new to dear imgui, see examples/README.txt and documentation at the top of imgui.cpp.
  // FIXME: 64-bit only for now! (Because sizeof(ImTextureId) == sizeof(void*))
  
  #include "imgui.h"
  #include "imgui_impl_win32.h"
  #include "imgui_impl_dx12.h"
  #include <d3d12.h>
  #include <dxgi1_4.h>
  #include <tchar.h>
  
  #define DX12_ENABLE_DEBUG_LAYER     0
  
  struct FrameContext
  {
      ID3D12CommandAllocator* CommandAllocator;
      UINT64                  FenceValue;
  };
  
  // Data
  static int const                    NUM_FRAMES_IN_FLIGHT = 3;
  static FrameContext                 g_frameContext[NUM_FRAMES_IN_FLIGHT] = {};
  static UINT                         g_frameIndex = 0;
  
  static int const                    NUM_BACK_BUFFERS = 3;
  static ID3D12Device*                g_pd3dDevice = NULL;
  static ID3D12DescriptorHeap*        g_pd3dRtvDescHeap = NULL;
  static ID3D12DescriptorHeap*        g_pd3dSrvDescHeap = NULL;
  static ID3D12CommandQueue*          g_pd3dCommandQueue = NULL;
  static ID3D12GraphicsCommandList*   g_pd3dCommandList = NULL;
  static ID3D12Fence*                 g_fence = NULL;
  static HANDLE                       g_fenceEvent = NULL;
  static UINT64                       g_fenceLastSignaledValue = 0;
  static IDXGISwapChain3*             g_pSwapChain = NULL;
  static HANDLE                       g_hSwapChainWaitableObject = NULL;
  static ID3D12Resource*              g_mainRenderTargetResource[NUM_BACK_BUFFERS] = {};
  static D3D12_CPU_DESCRIPTOR_HANDLE  g_mainRenderTargetDescriptor[NUM_BACK_BUFFERS] = {};
  
  // Forward declarations of helper functions
  bool CreateDeviceD3D(HWND hWnd);
  void CleanupDeviceD3D();
  void CreateRenderTarget();
  void CleanupRenderTarget();
  void WaitForLastSubmittedFrame();
  FrameContext*   WaitForNextFrameResources();
  void ResizeSwapChain(HWND hWnd, int width, int height);
  LRESULT WINAPI WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
  
  // Main code
  int main(int, char**)
  {
      // Create application window
      WNDCLASSEX wc = { sizeof(WNDCLASSEX), CS_CLASSDC, WndProc, 0L, 0L, GetModuleHandle(NULL), NULL, NULL, NULL, NULL, _T("ImGui Example"), NULL };
      ::RegisterClassEx(&wc);
      HWND hwnd = ::CreateWindow(wc.lpszClassName, _T("Dear ImGui DirectX12 Example"), WS_OVERLAPPEDWINDOW, 100, 100, 1280, 800, NULL, NULL, wc.hInstance, NULL);
  
      // Initialize Direct3D
      if (!CreateDeviceD3D(hwnd))
      {
          CleanupDeviceD3D();
          ::UnregisterClass(wc.lpszClassName, wc.hInstance);
          return 1;
      }
  
      // Show the window
      ::ShowWindow(hwnd, SW_SHOWDEFAULT);
      ::UpdateWindow(hwnd);
  
      // Setup Dear ImGui context
      IMGUI_CHECKVERSION();
      ImGui::CreateContext();
      ImGuiIO& io = ImGui::GetIO(); (void)io;
      //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls
      //io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;   // Enable Gamepad Controls
  
      // Setup Dear ImGui style
      ImGui::StyleColorsDark();
      //ImGui::StyleColorsClassic();
  
      // Setup Platform/Renderer bindings
      ImGui_ImplWin32_Init(hwnd);
      ImGui_ImplDX12_Init(g_pd3dDevice, NUM_FRAMES_IN_FLIGHT,
          DXGI_FORMAT_R8G8B8A8_UNORM,
          g_pd3dSrvDescHeap->GetCPUDescriptorHandleForHeapStart(),
          g_pd3dSrvDescHeap->GetGPUDescriptorHandleForHeapStart());
  
      // Load Fonts
      // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
      // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
      // - If the file cannot be loaded, the function will return NULL. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
      // - The fonts will be rasterized at a given size (w/ oversampling) and stored into a texture when calling ImFontAtlas::Build()/GetTexDataAsXXXX(), which ImGui_ImplXXXX_NewFrame below will call.
      // - Read 'misc/fonts/README.txt' for more instructions and details.
      // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
      //io.Fonts->AddFontDefault();
      //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf", 16.0f);
      //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 15.0f);
      //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf", 16.0f);
      //io.Fonts->AddFontFromFileTTF("../../misc/fonts/ProggyTiny.ttf", 10.0f);
      //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf", 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese());
      //IM_ASSERT(font != NULL);
  
      // Our state
      bool show_demo_window = true;
      bool show_another_window = false;
      ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
  
      // Main loop
      MSG msg;
      ZeroMemory(&msg, sizeof(msg));
      while (msg.message != WM_QUIT)
      {
          // Poll and handle messages (inputs, window resize, etc.)
          // You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
          // - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application.
          // - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application.
          // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
          if (::PeekMessage(&msg, NULL, 0U, 0U, PM_REMOVE))
          {
              ::TranslateMessage(&msg);
              ::DispatchMessage(&msg);
              continue;
          }
  
          // Start the Dear ImGui frame
          ImGui_ImplDX12_NewFrame();
          ImGui_ImplWin32_NewFrame();
          ImGui::NewFrame();
  
          // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
          if (show_demo_window)
              ImGui::ShowDemoWindow(&show_demo_window);
  
          // 2. Show a simple window that we create ourselves. We use a Begin/End pair to created a named window.
          {
              static float f = 0.0f;
              static int counter = 0;
  
              ImGui::Begin("Hello, world!");                          // Create a window called "Hello, world!" and append into it.
  
              ImGui::Text("This is some useful text.");               // Display some text (you can use a format strings too)
              ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
              ImGui::Checkbox("Another Window", &show_another_window);
  
              ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
              ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color
  
              if (ImGui::Button("Button"))                            // Buttons return true when clicked (most widgets return true when edited/activated)
                  counter++;
              ImGui::SameLine();
              ImGui::Text("counter = %d", counter);
  
              ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
              ImGui::End();
          }
  
          // 3. Show another simple window.
          if (show_another_window)
          {
              ImGui::Begin("Another Window", &show_another_window);   // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
              ImGui::Text("Hello from another window!");
              if (ImGui::Button("Close Me"))
                  show_another_window = false;
              ImGui::End();
          }
  
          // Rendering
          FrameContext* frameCtxt = WaitForNextFrameResources();
          UINT backBufferIdx = g_pSwapChain->GetCurrentBackBufferIndex();
          frameCtxt->CommandAllocator->Reset();
  
          D3D12_RESOURCE_BARRIER barrier = {};
          barrier.Type                   = D3D12_RESOURCE_BARRIER_TYPE_TRANSITION;
          barrier.Flags                  = D3D12_RESOURCE_BARRIER_FLAG_NONE;
          barrier.Transition.pResource   = g_mainRenderTargetResource[backBufferIdx];
          barrier.Transition.Subresource = D3D12_RESOURCE_BARRIER_ALL_SUBRESOURCES;
          barrier.Transition.StateBefore = D3D12_RESOURCE_STATE_PRESENT;
          barrier.Transition.StateAfter  = D3D12_RESOURCE_STATE_RENDER_TARGET;
  
          g_pd3dCommandList->Reset(frameCtxt->CommandAllocator, NULL);
          g_pd3dCommandList->ResourceBarrier(1, &barrier);
          g_pd3dCommandList->ClearRenderTargetView(g_mainRenderTargetDescriptor[backBufferIdx], (float*)&clear_color, 0, NULL);
          g_pd3dCommandList->OMSetRenderTargets(1, &g_mainRenderTargetDescriptor[backBufferIdx], FALSE, NULL);
          g_pd3dCommandList->SetDescriptorHeaps(1, &g_pd3dSrvDescHeap);
          ImGui::Render();
          ImGui_ImplDX12_RenderDrawData(ImGui::GetDrawData(), g_pd3dCommandList);
          barrier.Transition.StateBefore = D3D12_RESOURCE_STATE_RENDER_TARGET;
          barrier.Transition.StateAfter  = D3D12_RESOURCE_STATE_PRESENT;
          g_pd3dCommandList->ResourceBarrier(1, &barrier);
          g_pd3dCommandList->Close();
  
          g_pd3dCommandQueue->ExecuteCommandLists(1, (ID3D12CommandList* const*)&g_pd3dCommandList);
  
          g_pSwapChain->Present(1, 0); // Present with vsync
          //g_pSwapChain->Present(0, 0); // Present without vsync
  
          UINT64 fenceValue = g_fenceLastSignaledValue + 1;
          g_pd3dCommandQueue->Signal(g_fence, fenceValue);
          g_fenceLastSignaledValue = fenceValue;
          frameCtxt->FenceValue = fenceValue;
      }
  
      WaitForLastSubmittedFrame();
      ImGui_ImplDX12_Shutdown();
      ImGui_ImplWin32_Shutdown();
      ImGui::DestroyContext();
  
      CleanupDeviceD3D();
      ::DestroyWindow(hwnd);
      ::UnregisterClass(wc.lpszClassName, wc.hInstance);
  
      return 0;
  }
  
  // Helper functions
  
  bool CreateDeviceD3D(HWND hWnd)
  {
      // Setup swap chain
      DXGI_SWAP_CHAIN_DESC1 sd;
      {
          ZeroMemory(&sd, sizeof(sd));
          sd.BufferCount = NUM_BACK_BUFFERS;
          sd.Width = 0;
          sd.Height = 0;
          sd.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
          sd.Flags = DXGI_SWAP_CHAIN_FLAG_FRAME_LATENCY_WAITABLE_OBJECT;
          sd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
          sd.SampleDesc.Count = 1;
          sd.SampleDesc.Quality = 0;
          sd.SwapEffect = DXGI_SWAP_EFFECT_FLIP_DISCARD;
          sd.AlphaMode = DXGI_ALPHA_MODE_UNSPECIFIED;
          sd.Scaling = DXGI_SCALING_STRETCH;
          sd.Stereo = FALSE;
      }
  
      if (DX12_ENABLE_DEBUG_LAYER)
      {
          ID3D12Debug* dx12Debug = NULL;
          if (SUCCEEDED(D3D12GetDebugInterface(IID_PPV_ARGS(&dx12Debug))))
          {
              dx12Debug->EnableDebugLayer();
              dx12Debug->Release();
          }
      }
  
      D3D_FEATURE_LEVEL featureLevel = D3D_FEATURE_LEVEL_11_0;
      if (D3D12CreateDevice(NULL, featureLevel, IID_PPV_ARGS(&g_pd3dDevice)) != S_OK)
          return false;
  
      {
          D3D12_DESCRIPTOR_HEAP_DESC desc = {};
          desc.Type = D3D12_DESCRIPTOR_HEAP_TYPE_RTV;
          desc.NumDescriptors = NUM_BACK_BUFFERS;
          desc.Flags = D3D12_DESCRIPTOR_HEAP_FLAG_NONE;
          desc.NodeMask = 1;
          if (g_pd3dDevice->CreateDescriptorHeap(&desc, IID_PPV_ARGS(&g_pd3dRtvDescHeap)) != S_OK)
              return false;
  
          SIZE_T rtvDescriptorSize = g_pd3dDevice->GetDescriptorHandleIncrementSize(D3D12_DESCRIPTOR_HEAP_TYPE_RTV);
          D3D12_CPU_DESCRIPTOR_HANDLE rtvHandle = g_pd3dRtvDescHeap->GetCPUDescriptorHandleForHeapStart();
          for (UINT i = 0; i < NUM_BACK_BUFFERS; i++)
          {
              g_mainRenderTargetDescriptor[i] = rtvHandle;
              rtvHandle.ptr += rtvDescriptorSize;
          }
      }
  
      {
          D3D12_DESCRIPTOR_HEAP_DESC desc = {};
          desc.Type = D3D12_DESCRIPTOR_HEAP_TYPE_CBV_SRV_UAV;
          desc.NumDescriptors = 1;
          desc.Flags = D3D12_DESCRIPTOR_HEAP_FLAG_SHADER_VISIBLE;
          if (g_pd3dDevice->CreateDescriptorHeap(&desc, IID_PPV_ARGS(&g_pd3dSrvDescHeap)) != S_OK)
              return false;
      }
  
      {
          D3D12_COMMAND_QUEUE_DESC desc = {};
          desc.Type = D3D12_COMMAND_LIST_TYPE_DIRECT;
          desc.Flags = D3D12_COMMAND_QUEUE_FLAG_NONE;
          desc.NodeMask = 1;
          if (g_pd3dDevice->CreateCommandQueue(&desc, IID_PPV_ARGS(&g_pd3dCommandQueue)) != S_OK)
              return false;
      }
  
      for (UINT i = 0; i < NUM_FRAMES_IN_FLIGHT; i++)
          if (g_pd3dDevice->CreateCommandAllocator(D3D12_COMMAND_LIST_TYPE_DIRECT, IID_PPV_ARGS(&g_frameContext[i].CommandAllocator)) != S_OK)
              return false;
  
      if (g_pd3dDevice->CreateCommandList(0, D3D12_COMMAND_LIST_TYPE_DIRECT, g_frameContext[0].CommandAllocator, NULL, IID_PPV_ARGS(&g_pd3dCommandList)) != S_OK ||
          g_pd3dCommandList->Close() != S_OK)
          return false;
  
      if (g_pd3dDevice->CreateFence(0, D3D12_FENCE_FLAG_NONE, IID_PPV_ARGS(&g_fence)) != S_OK)
          return false;
  
      g_fenceEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
      if (g_fenceEvent == NULL)
          return false;
  
      {
          IDXGIFactory4* dxgiFactory = NULL;
          IDXGISwapChain1* swapChain1 = NULL;
          if (CreateDXGIFactory1(IID_PPV_ARGS(&dxgiFactory)) != S_OK ||
              dxgiFactory->CreateSwapChainForHwnd(g_pd3dCommandQueue, hWnd, &sd, NULL, NULL, &swapChain1) != S_OK ||
              swapChain1->QueryInterface(IID_PPV_ARGS(&g_pSwapChain)) != S_OK)
              return false;
          swapChain1->Release();
          dxgiFactory->Release();
          g_pSwapChain->SetMaximumFrameLatency(NUM_BACK_BUFFERS);
          g_hSwapChainWaitableObject = g_pSwapChain->GetFrameLatencyWaitableObject();
      }
  
      CreateRenderTarget();
      return true;
  }
  
  void CleanupDeviceD3D()
  {
      CleanupRenderTarget();
      if (g_pSwapChain) { g_pSwapChain->Release(); g_pSwapChain = NULL; }
      if (g_hSwapChainWaitableObject != NULL) { CloseHandle(g_hSwapChainWaitableObject); }
      for (UINT i = 0; i < NUM_FRAMES_IN_FLIGHT; i++)
          if (g_frameContext[i].CommandAllocator) { g_frameContext[i].CommandAllocator->Release(); g_frameContext[i].CommandAllocator = NULL; }
      if (g_pd3dCommandQueue) { g_pd3dCommandQueue->Release(); g_pd3dCommandQueue = NULL; }
      if (g_pd3dCommandList) { g_pd3dCommandList->Release(); g_pd3dCommandList = NULL; }
      if (g_pd3dRtvDescHeap) { g_pd3dRtvDescHeap->Release(); g_pd3dRtvDescHeap = NULL; }
      if (g_pd3dSrvDescHeap) { g_pd3dSrvDescHeap->Release(); g_pd3dSrvDescHeap = NULL; }
      if (g_fence) { g_fence->Release(); g_fence = NULL; }
      if (g_fenceEvent) { CloseHandle(g_fenceEvent); g_fenceEvent = NULL; }
      if (g_pd3dDevice) { g_pd3dDevice->Release(); g_pd3dDevice = NULL; }
  }
  
  void CreateRenderTarget()
  {
      ID3D12Resource* pBackBuffer;
      for (UINT i = 0; i < NUM_BACK_BUFFERS; i++)
      {
          g_pSwapChain->GetBuffer(i, IID_PPV_ARGS(&pBackBuffer));
          g_pd3dDevice->CreateRenderTargetView(pBackBuffer, NULL, g_mainRenderTargetDescriptor[i]);
          g_mainRenderTargetResource[i] = pBackBuffer;
      }
  }
  
  void CleanupRenderTarget()
  {
      WaitForLastSubmittedFrame();
  
      for (UINT i = 0; i < NUM_BACK_BUFFERS; i++)
          if (g_mainRenderTargetResource[i]) { g_mainRenderTargetResource[i]->Release(); g_mainRenderTargetResource[i] = NULL; }
  }
  
  void WaitForLastSubmittedFrame()
  {
      FrameContext* frameCtxt = &g_frameContext[g_frameIndex % NUM_FRAMES_IN_FLIGHT];
  
      UINT64 fenceValue = frameCtxt->FenceValue;
      if (fenceValue == 0)
          return; // No fence was signaled
  
      frameCtxt->FenceValue = 0;
      if (g_fence->GetCompletedValue() >= fenceValue)
          return;
  
      g_fence->SetEventOnCompletion(fenceValue, g_fenceEvent);
      WaitForSingleObject(g_fenceEvent, INFINITE);
  }
  
  FrameContext* WaitForNextFrameResources()
  {
      UINT nextFrameIndex = g_frameIndex + 1;
      g_frameIndex = nextFrameIndex;
  
      HANDLE waitableObjects[] = { g_hSwapChainWaitableObject, NULL };
      DWORD numWaitableObjects = 1;
  
      FrameContext* frameCtxt = &g_frameContext[nextFrameIndex % NUM_FRAMES_IN_FLIGHT];
      UINT64 fenceValue = frameCtxt->FenceValue;
      if (fenceValue != 0) // means no fence was signaled
      {
          frameCtxt->FenceValue = 0;
          g_fence->SetEventOnCompletion(fenceValue, g_fenceEvent);
          waitableObjects[1] = g_fenceEvent;
          numWaitableObjects = 2;
      }
  
      WaitForMultipleObjects(numWaitableObjects, waitableObjects, TRUE, INFINITE);
  
      return frameCtxt;
  }
  
  void ResizeSwapChain(HWND hWnd, int width, int height)
  {
      DXGI_SWAP_CHAIN_DESC1 sd;
      g_pSwapChain->GetDesc1(&sd);
      sd.Width = width;
      sd.Height = height;
  
      IDXGIFactory4* dxgiFactory = NULL;
      g_pSwapChain->GetParent(IID_PPV_ARGS(&dxgiFactory));
  
      g_pSwapChain->Release();
      CloseHandle(g_hSwapChainWaitableObject);
  
      IDXGISwapChain1* swapChain1 = NULL;
      dxgiFactory->CreateSwapChainForHwnd(g_pd3dCommandQueue, hWnd, &sd, NULL, NULL, &swapChain1);
      swapChain1->QueryInterface(IID_PPV_ARGS(&g_pSwapChain));
      swapChain1->Release();
      dxgiFactory->Release();
  
      g_pSwapChain->SetMaximumFrameLatency(NUM_BACK_BUFFERS);
  
      g_hSwapChainWaitableObject = g_pSwapChain->GetFrameLatencyWaitableObject();
      assert(g_hSwapChainWaitableObject != NULL);
  }
  
  // Win32 message handler
  extern LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
  LRESULT WINAPI WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
  {
      if (ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam))
          return true;
  
      switch (msg)
      {
      case WM_SIZE:
          if (g_pd3dDevice != NULL && wParam != SIZE_MINIMIZED)
          {
              ImGui_ImplDX12_InvalidateDeviceObjects();
              CleanupRenderTarget();
              ResizeSwapChain(hWnd, (UINT)LOWORD(lParam), (UINT)HIWORD(lParam));
              CreateRenderTarget();
              ImGui_ImplDX12_CreateDeviceObjects();
          }
          return 0;
      case WM_SYSCOMMAND:
          if ((wParam & 0xfff0) == SC_KEYMENU) // Disable ALT application menu
              return 0;
          break;
      case WM_DESTROY:
          ::PostQuitMessage(0);
          return 0;
      }
      return ::DefWindowProc(hWnd, msg, wParam, lParam);
  }
  