GLAD with wgl

CMakeLists.txt

cmake_minimum_required(VERSION 3.8)

# .
# ├── CMakeLists.txt
# ├── GladWGL.cpp
# └── glad
#     ├── include
#     │   ├── KHR
#     │   │   └── khrplatform.h
#     │   └── glad
#     │       └── glad.h
#     └── src
#         └── glad.c

# 5 directories, 5 files

include_directories(glad/include)

# Add source to this project's executable.
add_executable (GladWGL WIN32 "GladWGL.cpp" "glad/src/glad.c")

if (CMAKE_VERSION VERSION_GREATER 3.12)
  set_property(TARGET GladWGL PROPERTY CXX_STANDARD 20)
endif()

GladWGL.cpp

// GladWGL.cpp : Defines the entry point for the application.
// https://www.khronos.org/opengl/wiki/Creating_an_OpenGL_Context_%28WGL%29

#include <windows.h>
// #include <GL/GL.h>
#include <glad/glad.h>

#pragma comment (lib, "opengl32.lib")

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
HINSTANCE hinst;
HWND hwndMain;

// https://www.khronos.org/opengl/wiki/Load_OpenGL_Functions
void *GetAnyGLFuncAddress(const char *name)
{
    void *p = (void *)wglGetProcAddress(name);
    if (p == 0 ||
       (p == (void*)0x1) || (p == (void*)0x2) || (p == (void*)0x3) ||
       (p == (void*)-1) )
    {
        HMODULE module = LoadLibraryA("opengl32.dll");
        p = (void *)GetProcAddress(module, name);
    }

    return p;
}

int WinMain(__in HINSTANCE hInstance, __in_opt HINSTANCE hPrevInstance, __in_opt LPSTR lpCmdLine, __in int nShowCmd)
{
    hinst = hInstance;
    
    MSG msg = { 0 };
    WNDCLASS wc = { 0 };
    wc.lpfnWndProc = WndProc;
    wc.hInstance = hInstance;
    wc.hbrBackground = (HBRUSH)(COLOR_BACKGROUND);
    wc.lpszClassName = "oglversionchecksample";
    wc.style = CS_OWNDC;
    if (!RegisterClass(&wc))
        return 1;
    hwndMain = CreateWindow(wc.lpszClassName, "openglversioncheck", WS_OVERLAPPEDWINDOW | WS_VISIBLE, 0, 0, 640, 480, 0, 0, hInstance, 0);
    if (!hwndMain)
        return FALSE;

    ShowWindow(hwndMain, nShowCmd);
    UpdateWindow(hwndMain);

    while (GetMessage(&msg, NULL, 0, 0) > 0) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return 0;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_CREATE:
    {
        PIXELFORMATDESCRIPTOR pfd =
        {
            sizeof(PIXELFORMATDESCRIPTOR),
            1,
            PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,    //Flags
            PFD_TYPE_RGBA,        // The kind of framebuffer. RGBA or palette.
            32,                   // Colordepth of the framebuffer.
            0, 0, 0, 0, 0, 0,
            0,
            0,
            0,
            0, 0, 0, 0,
            24,                   // Number of bits for the depthbuffer
            8,                    // Number of bits for the stencilbuffer
            0,                    // Number of Aux buffers in the framebuffer.
            PFD_MAIN_PLANE,
            0,
            0, 0, 0
        };

        HDC ourWindowHandleToDeviceContext = GetDC(hWnd);

        int  letWindowsChooseThisPixelFormat;
        letWindowsChooseThisPixelFormat = ChoosePixelFormat(ourWindowHandleToDeviceContext, &pfd);
        SetPixelFormat(ourWindowHandleToDeviceContext, letWindowsChooseThisPixelFormat, &pfd);

        HGLRC ourOpenGLRenderingContext = wglCreateContext(ourWindowHandleToDeviceContext);
        wglMakeCurrent(ourWindowHandleToDeviceContext, ourOpenGLRenderingContext);

        if (!gladLoadGLLoader((GLADloadproc)GetAnyGLFuncAddress)) {
            MessageBoxA(0, "Failed to initialize GLAD", "Error", 0);
            PostQuitMessage(0);
        } else {
            MessageBoxA(0, (char *)glGetString(GL_VERSION), "OPENGL VERSION", 0);
        }

        //wglMakeCurrent(ourWindowHandleToDeviceContext, NULL); Unnecessary; wglDeleteContext will make the context not current
        wglDeleteContext(ourOpenGLRenderingContext);
    }
    break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;

}