#include <windows.h>

#include <gl/gl.h>



LRESULT CALLBACK WindowProc(HWND, UINT, WPARAM, LPARAM);

void EnableOpenGL(HWND hwnd, HDC*, HGLRC*);

void DisableOpenGL(HWND, HDC, HGLRC);



int WINAPI WinMain(HINSTANCE hInstance,

                   HINSTANCE hPrevInstance,

                   LPSTR lpCmdLine,

                   int nCmdShow)

{

    WNDCLASSEX wcex;

    HWND hwnd;

    HDC hDC;

    HGLRC hRC;

    MSG msg;

    BOOL bQuit = FALSE;

    float theta = 0.0f;



    /* register window class */

    wcex.cbSize = sizeof(WNDCLASSEX);

    wcex.style = CS_OWNDC;

    wcex.lpfnWndProc = WindowProc;

    wcex.cbClsExtra = 0;

    wcex.cbWndExtra = 0;

    wcex.hInstance = hInstance;

    wcex.hIcon = LoadIcon(NULL, IDI_APPLICATION);

    wcex.hCursor = LoadCursor(NULL, IDC_ARROW);

    wcex.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);

    wcex.lpszMenuName = NULL;

    wcex.lpszClassName = "GLSample";

    wcex.hIconSm = LoadIcon(NULL, IDI_APPLICATION);;





    if (!RegisterClassEx(&wcex))

        return 0;



    /* create main window */

    hwnd = CreateWindowEx(0,

                          "GLSample",

                          "OpenGL Sample",

                          WS_OVERLAPPEDWINDOW,

                          CW_USEDEFAULT,

                          CW_USEDEFAULT,

                          256,

                          256,

                          NULL,

                          NULL,

                          hInstance,

                          NULL);



    ShowWindow(hwnd, nCmdShow);



    /* enable OpenGL for the window */

    EnableOpenGL(hwnd, &hDC, &hRC);



    /* program main loop */

    while (!bQuit)

    {

        /* check for messages */

        if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))

        {

            /* handle or dispatch messages */

            if (msg.message == WM_QUIT)

            {

                bQuit = TRUE;

            }

            else

            {

                TranslateMessage(&msg);

                DispatchMessage(&msg);

            }

        }

        else

        {

            /* OpenGL animation code goes here */



            glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

            glClear(GL_COLOR_BUFFER_BIT);



            glPushMatrix();

            glRotatef(theta, 0.0f, 0.0f, 1.0f);



            glBegin(GL_TRIANGLES);



                glColor3f(1.0f, 0.0f, 0.0f);   glVertex2f(0.0f,   1.0f);

                glColor3f(0.0f, 1.0f, 0.0f);   glVertex2f(0.87f,  -0.5f);

                glColor3f(0.0f, 0.0f, 1.0f);   glVertex2f(-0.87f, -0.5f);



            glEnd();



            glPopMatrix();



            SwapBuffers(hDC);



            theta += 1.0f;

            Sleep (1);

        }

    }



    /* shutdown OpenGL */

    DisableOpenGL(hwnd, hDC, hRC);



    /* destroy the window explicitly */

    DestroyWindow(hwnd);



    return msg.wParam;

}



LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)

{

    switch (uMsg)

    {

        case WM_CLOSE:

            PostQuitMessage(0);

        break;



        case WM_DESTROY:

            return 0;



        case WM_KEYDOWN:

        {

            switch (wParam)

            {

                case VK_ESCAPE:

                    PostQuitMessage(0);

                break;

            }

        }

        break;



        default:

            return DefWindowProc(hwnd, uMsg, wParam, lParam);

    }



    return 0;

}



void EnableOpenGL(HWND hwnd, HDC* hDC, HGLRC* hRC)

{

    PIXELFORMATDESCRIPTOR pfd;



    int iFormat;



    /* get the device context (DC) */

    *hDC = GetDC(hwnd);



    /* set the pixel format for the DC */

    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 = 16;

    pfd.iLayerType = PFD_MAIN_PLANE;



    iFormat = ChoosePixelFormat(*hDC, &pfd);



    SetPixelFormat(*hDC, iFormat, &pfd);



    /* create and enable the render context (RC) */

    *hRC = wglCreateContext(*hDC);



    wglMakeCurrent(*hDC, *hRC);

}



void DisableOpenGL (HWND hwnd, HDC hDC, HGLRC hRC)

{

    wglMakeCurrent(NULL, NULL);

    wglDeleteContext(hRC);

    ReleaseDC(hwnd, hDC);

}