imgui/imgui_windows_main.cpp

#include "imgui.h"
#include "imgui_impl_dx11.h"
#include "imgui_impl_win32.h"
#include <d3d11.h>
#include <tchar.h>
#include <thread>

#include "imgui_main.h"

// Data
static ID3D11Device*            g_pd3dDevice = nullptr;
static ID3D11DeviceContext*     g_pd3dDeviceContext = nullptr;
static IDXGISwapChain*          g_pSwapChain = nullptr;
static bool                     g_SwapChainOccluded = false;
static UINT                     g_ResizeWidth = 0, g_ResizeHeight = 0;
static ID3D11RenderTargetView*  g_mainRenderTargetView = nullptr;
static HWND                     hwnd = nullptr;
static WNDCLASSEXW              wc;

// Forward declarations of helper functions
bool CreateDeviceD3D(HWND hWnd);
void CleanupDeviceD3D();
void CreateRenderTarget();
void CleanupRenderTarget();
LRESULT WINAPI WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

// Main code
int init_imgui() {
    // Create application window
    ImGui_ImplWin32_EnableDpiAwareness();
    wc = { sizeof(wc), CS_CLASSDC, WndProc, 0L, 0L, GetModuleHandle(nullptr), nullptr, nullptr, nullptr, nullptr, L"Arona", nullptr };
    ::RegisterClassExW(&wc);
    std::string window_title = get_window_title();
    wchar_t window_title_wchar[256];
    MultiByteToWideChar(CP_ACP, 0, window_title.c_str(), -1, window_title_wchar, 256);
    hwnd = ::CreateWindowW(wc.lpszClassName, window_title_wchar, WS_OVERLAPPEDWINDOW, 100, 100, 1280, 800, nullptr, nullptr, wc.hInstance, nullptr);

    // Initialize Direct3D
    if (!CreateDeviceD3D(hwnd))
    {
        CleanupDeviceD3D();
        ::UnregisterClassW(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;

    configure_imgui(io);

    // Setup Platform/Renderer backends
    ImGui_ImplWin32_Init(hwnd);
    ImGui_ImplDX11_Init(g_pd3dDevice, g_pd3dDeviceContext);
    return 0;
}

bool imgui_new_frame() {
    // Poll and handle messages (inputs, window resize, etc.)
    // See the WndProc() function below for our to dispatch events to the Win32 backend.
    MSG msg;
    bool done = false;
    while (::PeekMessage(&msg, nullptr, 0U, 0U, PM_REMOVE))
    {
        ::TranslateMessage(&msg);
        ::DispatchMessage(&msg);
        if (msg.message == WM_QUIT)
            done = true;
    }
    if (done)
        return false;

    // Handle window being minimized or screen locked
    if (g_SwapChainOccluded && g_pSwapChain->Present(1, DXGI_PRESENT_TEST) == DXGI_STATUS_OCCLUDED)
    {
        ::Sleep(10);
        return true;
    }
    g_SwapChainOccluded = false;

    // Handle window resize (we don't resize directly in the WM_SIZE handler)
    if (g_ResizeWidth != 0 && g_ResizeHeight != 0)
    {
        CleanupRenderTarget();
        g_pSwapChain->ResizeBuffers(0, g_ResizeWidth, g_ResizeHeight, DXGI_FORMAT_UNKNOWN, 0);
        g_ResizeWidth = g_ResizeHeight = 0;
        CreateRenderTarget();
    }

    // Start the Dear ImGui frame
    ImGui_ImplDX11_NewFrame();
    ImGui_ImplWin32_NewFrame();
    ImGui::NewFrame();
    return true;
}

void render_imgui() {
    // Rendering
    ImGui::Render();
    ImGuiIO& io = ImGui::GetIO();
    ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
    const float clear_color_with_alpha[4] = { clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w };
    g_pd3dDeviceContext->OMSetRenderTargets(1, &g_mainRenderTargetView, nullptr);
    g_pd3dDeviceContext->ClearRenderTargetView(g_mainRenderTargetView, clear_color_with_alpha);
    ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());

    // Update and Render additional Platform Windows
    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
    {
        ImGui::UpdatePlatformWindows();
        ImGui::RenderPlatformWindowsDefault();
    }

    // Present
    HRESULT hr = g_pSwapChain->Present(1, 0);   // Present with vsync
    //HRESULT hr = g_pSwapChain->Present(0, 0); // Present without vsync
    g_SwapChainOccluded = (hr == DXGI_STATUS_OCCLUDED);
}

void shutdown_imgui() {
    // Cleanup
    ImGui_ImplDX11_Shutdown();
    ImGui_ImplWin32_Shutdown();
    ImGui::DestroyContext();

    CleanupDeviceD3D();
    ::DestroyWindow(hwnd);
    ::UnregisterClassW(wc.lpszClassName, wc.hInstance);
}

float get_dpi_scale() {
    return ImGui_ImplWin32_GetDpiScaleForHwnd(hwnd);
}

void run_imgui() {
    init_imgui();
    while (true) {
        if (!imgui_new_frame()) {
            break;
        }
        ImGuiIO& io = ImGui::GetIO();
        tick_imgui(io.DeltaTime);
        draw_imgui(io.DeltaTime);
        render_imgui();
        std::this_thread::yield();
    }
    shutdown_imgui();
}

// Helper functions
bool CreateDeviceD3D(HWND hWnd) {
    // Setup swap chain
    DXGI_SWAP_CHAIN_DESC sd;
    ZeroMemory(&sd, sizeof(sd));
    sd.BufferCount = 2;
    sd.BufferDesc.Width = 0;
    sd.BufferDesc.Height = 0;
    sd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    sd.BufferDesc.RefreshRate.Numerator = 60;
    sd.BufferDesc.RefreshRate.Denominator = 1;
    sd.Flags = DXGI_SWAP_CHAIN_FLAG_ALLOW_MODE_SWITCH;
    sd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
    sd.OutputWindow = hWnd;
    sd.SampleDesc.Count = 1;
    sd.SampleDesc.Quality = 0;
    sd.Windowed = TRUE;
    sd.SwapEffect = DXGI_SWAP_EFFECT_DISCARD;

    UINT createDeviceFlags = 0;
    //createDeviceFlags |= D3D11_CREATE_DEVICE_DEBUG;
    D3D_FEATURE_LEVEL featureLevel;
    const D3D_FEATURE_LEVEL featureLevelArray[2] = { D3D_FEATURE_LEVEL_11_0, D3D_FEATURE_LEVEL_10_0, };
    HRESULT res = D3D11CreateDeviceAndSwapChain(nullptr, D3D_DRIVER_TYPE_HARDWARE, nullptr, createDeviceFlags, featureLevelArray, 2, D3D11_SDK_VERSION, &sd, &g_pSwapChain, &g_pd3dDevice, &featureLevel, &g_pd3dDeviceContext);
    if (res == DXGI_ERROR_UNSUPPORTED) // Try high-performance WARP software driver if hardware is not available.
        res = D3D11CreateDeviceAndSwapChain(nullptr, D3D_DRIVER_TYPE_WARP, nullptr, createDeviceFlags, featureLevelArray, 2, D3D11_SDK_VERSION, &sd, &g_pSwapChain, &g_pd3dDevice, &featureLevel, &g_pd3dDeviceContext);
    if (res != S_OK)
        return false;

    CreateRenderTarget();
    return true;
}

void CleanupDeviceD3D() {
    CleanupRenderTarget();
    if (g_pSwapChain) { g_pSwapChain->Release(); g_pSwapChain = nullptr; }
    if (g_pd3dDeviceContext) { g_pd3dDeviceContext->Release(); g_pd3dDeviceContext = nullptr; }
    if (g_pd3dDevice) { g_pd3dDevice->Release(); g_pd3dDevice = nullptr; }
}

void CreateRenderTarget() {
    ID3D11Texture2D* pBackBuffer;
    g_pSwapChain->GetBuffer(0, IID_PPV_ARGS(&pBackBuffer));
    g_pd3dDevice->CreateRenderTargetView(pBackBuffer, nullptr, &g_mainRenderTargetView);
    pBackBuffer->Release();
}

void CleanupRenderTarget() {
    if (g_mainRenderTargetView) { g_mainRenderTargetView->Release(); g_mainRenderTargetView = nullptr; }
}

// Forward declare message handler from imgui_impl_win32.cpp
extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

// Win32 message handler
// 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, or clear/overwrite your copy of the mouse data.
// - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application, or clear/overwrite your copy of the keyboard data.
// Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
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 (wParam == SIZE_MINIMIZED)
                return 0;
            g_ResizeWidth = (UINT)LOWORD(lParam); // Queue resize
            g_ResizeHeight = (UINT)HIWORD(lParam);
            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 ::DefWindowProcW(hWnd, msg, wParam, lParam);
}