quyse/flaw

#define STRICT
#define WIN32_LEAN_AND_MEAN
#define UNICODE
#define _UNICODE
#define _WIN32_WINNT 0x0501
#include <windows.h>
#include <windowsx.h>

typedef HGLRC (WINAPI *PFNWGLCREATECONTEXTATTRIBSARBPROC)(HDC hDC, HGLRC hShareContext, const int* attribList);

#define WGL_CONTEXT_MAJOR_VERSION_ARB 0x2091
#define WGL_CONTEXT_MINOR_VERSION_ARB 0x2092
#define WGL_CONTEXT_FLAGS_ARB 0x2094
#define WGL_CONTEXT_PROFILE_MASK_ARB 0x9126
#define WGL_CONTEXT_DEBUG_BIT_ARB 0x0001
#define WGL_CONTEXT_CORE_PROFILE_BIT_ARB 0x00000001

HDC initWin32OpenGLContext(HWND hWnd, int debug, HGLRC* phglrcMain, HGLRC* phglrcBackground)
{
    // get window's persistent HDC
    HDC hdc = GetDC(hWnd);
    if(!hdc) return NULL;

    // choose & set pixel format
    PIXELFORMATDESCRIPTOR pfd;
    ZeroMemory(&pfd, sizeof(pfd));
    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 = 24;
    pfd.cDepthBits = 0;
    pfd.iLayerType = PFD_MAIN_PLANE;
    int pixelFormat = ChoosePixelFormat(hdc, &pfd);
    if(!pixelFormat) return NULL;
    if(!SetPixelFormat(hdc, pixelFormat, &pfd)) return NULL;

    // create temporary context and make it current
    HGLRC hglrcTemp = wglCreateContext(hdc);
    if(!wglMakeCurrent(hdc, hglrcTemp)) return NULL;

    // create real context
    int attribs[] =
    {
        WGL_CONTEXT_MAJOR_VERSION_ARB, 0,
        WGL_CONTEXT_MINOR_VERSION_ARB, 0,
        WGL_CONTEXT_FLAGS_ARB, debug ? WGL_CONTEXT_DEBUG_BIT_ARB : 0,
        WGL_CONTEXT_PROFILE_MASK_ARB, WGL_CONTEXT_CORE_PROFILE_BIT_ARB,
        0, 0
    };
    // versions to try
    static const int versions[][2] =
    {
        { 4, 3 },
        { 4, 2 },
        { 4, 1 },
        { 4, 0 },
        { 3, 3 },
    };
    PFNWGLCREATECONTEXTATTRIBSARBPROC wglCreateContextAttribsARB = (PFNWGLCREATECONTEXTATTRIBSARBPROC)wglGetProcAddress("wglCreateContextAttribsARB");
    if(!wglCreateContextAttribsARB)
    {
        wglMakeCurrent(hdc, NULL);
        wglDeleteContext(hglrcTemp);
        return NULL;
    }
    // loop for versions
    HGLRC hglrcMain = NULL, hglrcBackground = NULL;
    for(int i = 0; i < sizeof(versions) / sizeof(versions[0]); ++i)
    {
        attribs[1] = versions[i][0];
        attribs[3] = versions[i][1];
        hglrcMain = wglCreateContextAttribsARB(hdc, 0, attribs);
        hglrcBackground = wglCreateContextAttribsARB(hdc, 0, attribs);
        if(hglrcMain && hglrcBackground) break;
        if(hglrcMain) wglDeleteContext(hglrcMain);
        if(hglrcBackground) wglDeleteContext(hglrcBackground);
    }

    // delete temporary context
    wglMakeCurrent(hdc, NULL);
    wglDeleteContext(hglrcTemp);

    // if no version is supported, bummer
    if(!hglrcMain || !hglrcBackground) return NULL;

    // make contexts share resources
    if(!wglShareLists(hglrcMain, hglrcBackground))
    {
        wglDeleteContext(hglrcMain);
        wglDeleteContext(hglrcBackground);
        return NULL;
    }

    *phglrcMain = hglrcMain;
    *phglrcBackground = hglrcBackground;
    return hdc;
}

int setCurrentWin32OpenGLContext(HDC hdc, HGLRC hglrc)
{
    return wglMakeCurrent(hdc, hglrc);
}

void deinitWin32OpenGLContext(HWND hWnd, HGLRC hglrc)
{
    wglMakeCurrent(GetDC(hWnd), hglrc);
    wglDeleteContext(hglrc);
}

void swapWin32OpenGLWindow(HDC hdc)
{
    SwapBuffers(hdc);
}