imgui/examples/example_win32_opengl3/main.cpp

// dear imgui: standalone example application for OpenGL3 with Winapi
// If you are new to dear imgui, see examples/README.txt and documentation at the top of imgui.cpp.

#include "imgui.h"
#include "imgui_impl_opengl3.h"
#include "imgui_impl_win32.h"
#include <windows.h>
#include <GL/GL.h>
#include <tchar.h>

// Data stored per platform window
struct RendererData
{
    HDC hDC;
};

// Data
HGLRC g_hRC;
RendererData g_MainWindow;
static int g_Width;
static int g_Height;

// Forward declarations of helper functions
static bool CreateDeviceOpenGL3(HWND hWnd, RendererData* data);
static void CleanupDeviceOpenGL3(HWND hWnd, RendererData* data);
LRESULT WINAPI WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

// Main code
int main(int, char**)
{
    // Create application window
    //ImGui_ImplWin32_EnableDpiAwareness();
    WNDCLASSEX wc = { sizeof(WNDCLASSEX), CS_OWNDC, WndProc, 0L, 0L, GetModuleHandle(NULL), NULL, NULL, NULL, NULL, _T("ImGui Example"), NULL };
    ::RegisterClassEx(&wc);
    HWND hwnd = ::CreateWindow(wc.lpszClassName, _T("Dear ImGui Winapi+OpenGL3 Example"), WS_OVERLAPPEDWINDOW, 100, 100, 1280, 800, NULL, NULL, wc.hInstance, NULL);

    // Initialize OpenGL3
    if (!CreateDeviceOpenGL3(hwnd, &g_MainWindow))
    {
        CleanupDeviceOpenGL3(hwnd, &g_MainWindow);
        ::DestroyWindow(hwnd);
        ::UnregisterClass(wc.lpszClassName, wc.hInstance);
        return 1;
    }

    wglMakeCurrent(g_MainWindow.hDC, g_hRC);

    // 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_InitForOpenGL(hwnd);
    ImGui_ImplOpenGL3_Init();

    // 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 'docs/FONTS.md' 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_ImplOpenGL3_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
        ImGui::Render();
        glViewport(0, 0, g_Width, g_Height);
        glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
        glClear(GL_COLOR_BUFFER_BIT);

        // If you are using this code with non-legacy OpenGL header/contexts (which you should not, prefer using imgui_impl_opengl3.cpp!!),
        // you may need to backup/reset/restore current shader using the commented lines below.
        //GLint last_program;
        //glGetIntegerv(GL_CURRENT_PROGRAM, &last_program);
        //glUseProgram(0);
        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
        //glUseProgram(last_program);

        SwapBuffers(g_MainWindow.hDC);
    }

    ImGui_ImplOpenGL3_Shutdown();
    ImGui_ImplWin32_Shutdown();
    ImGui::DestroyContext();

    CleanupDeviceOpenGL3(hwnd, &g_MainWindow);
    wglDeleteContext(g_hRC);
    ::DestroyWindow(hwnd);
    ::UnregisterClass(wc.lpszClassName, wc.hInstance);

    return 0;
}

static bool ActivateOpenGL3(HWND hWnd)
{
    HDC hDc = GetDC(hWnd);

    PIXELFORMATDESCRIPTOR pfd = { 0 };

    pfd.nSize = sizeof(pfd);
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.cColorBits = 32;

    int pf = ChoosePixelFormat(hDc, &pfd);
    if (pf == 0)
    {
        return false;
    }

    if (SetPixelFormat(hDc, pf, &pfd) == FALSE)
    {
        return false;
    }

    ReleaseDC(hWnd, hDc);
    return true;
}

// Helper functions

static bool CreateDeviceOpenGL3(HWND hWnd, RendererData* data)
{
    if (!ActivateOpenGL3(hWnd))
        return false;

    data->hDC = GetDC(hWnd);

    if (!g_hRC)
    {
        g_hRC = wglCreateContext(data->hDC);
    }

    return true;
}

static void CleanupDeviceOpenGL3(HWND hWnd, RendererData* data)
{
    wglMakeCurrent(NULL, NULL);
    ReleaseDC(hWnd, data->hDC);
}

// 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
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)
        {
            g_Width = LOWORD(lParam);
            g_Height = 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 ::DefWindowProc(hWnd, msg, wParam, lParam);
}