/**************************
 * Includes que tenemos que añadir
 **************************/
#include <windows.h>
#include <gl/gl.h>

/**************************
 * Declaraciones de funciones que dejamos como están
 **************************/
LRESULT CALLBACK WndProc (HWND hWnd, UINT message,
WPARAM wParam, LPARAM lParam);
void EnableOpenGL (HWND hWnd, HDC *hDC, HGLRC *hRC);
void DisableOpenGL (HWND hWnd, HDC hDC, HGLRC hRC);

void main () {
    WNDCLASS wc;
    HWND hWnd;
    HDC hDC;
    HGLRC hRC;        
    MSG msg;
    BOOL bQuit = FALSE;
    float theta = 0.0f;

    wc.style = CS_OWNDC;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor (NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH) GetStockObject (BLACK_BRUSH);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = "Ventana";
    RegisterClass (&wc);

    hWnd = CreateWindow (
      "Ventana", "Título de la ventana", 
      WS_CAPTION | WS_POPUPWINDOW | WS_VISIBLE,
      0, 0, 256, 256,
      NULL, NULL, 0, NULL);

    EnableOpenGL (hWnd, &hDC, &hRC);
    while (!bQuit)
    {
         if (PeekMessage (&msg, NULL, 0, 0, PM_REMOVE))
        {
             if (msg.message == WM_QUIT)
            {
                bQuit = TRUE;
            }
            else
            {
                TranslateMessage (&msg);
                DispatchMessage (&msg);
            }
        }
        else
        {
            glClearColor (0.0f, 0.0f, 0.0f, 0.0f);//RGBalfa
            glClear (GL_COLOR_BUFFER_BIT);

            glPushMatrix ();
            glRotatef (theta, 0.0f, 0.0f, 1.0f);//angulo,xcentro,ycentro,zcentro
            //Existe Translate
            glBegin (GL_TRIANGLES);
            /*
            GL_LINES Treats each pair of vertices as an independent line segment.
                        
GL_LINE_STRIP  Draws a connected group of line segments from the first vertex
                            to the last.
                         
GL_LINE_LOOP Draws a connected group of line segments from the first vertex
                            to the last, then back to the first.
                         
GL_TRIANGLES Treats each triplet of vertices as an independent triangle.
 
GL_QUADS  Treats each group of four vertices as an independent quadrilateral.

GL_POLYGON  Draws a single, convex polygon.
*/
            glColor3f (1.0f, 0.0f, 0.0f);   glVertex2f (0.0f, 1.0f); //Origen en el centro, 1 a cada borde
            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);
            Sleep (1);
        }
    }

    DisableOpenGL (hWnd, hDC, hRC);
    DestroyWindow (hWnd);
}

LRESULT CALLBACK WndProc (HWND hWnd, UINT message,
                          WPARAM wParam, LPARAM lParam)
{

    switch (message)
    {
    case WM_CREATE:
        return 0;
    case WM_CLOSE:
        PostQuitMessage (0);
        return 0;
    case WM_DESTROY:
        return 0;

    case WM_KEYDOWN:
        switch (wParam)
        {
        case VK_ESCAPE:
            PostQuitMessage(0);
            return 0;
        }
        return 0;
    default:
        return DefWindowProc (hWnd, message, wParam, lParam);
    }
}

void EnableOpenGL (HWND hWnd, HDC *hDC, HGLRC *hRC)
{
    PIXELFORMATDESCRIPTOR pfd;
    int iFormat;

    *hDC = GetDC (hWnd);

    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);

    *hRC = wglCreateContext( *hDC );
    wglMakeCurrent( *hDC, *hRC );
}


void DisableOpenGL (HWND hWnd, HDC hDC, HGLRC hRC)
{
    wglMakeCurrent (NULL, NULL);
    wglDeleteContext (hRC);
    ReleaseDC (hWnd, hDC);
}