// -----------------------------------------------------------------
// Een voorbeeld va een minimaal Win32 en OpenGL programma.
// Maakt gebruik van een MS Windows venster. 
// Het werkt alleen in 16 bit kleuren mode of hoger.
// (c) Hein Pragt 2010 vrij te gebruiken.
// -----------------------------------------------------------------

#include <windows.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <stdio.h>

// OpenGL code

void display()
{
  glClear(GL_COLOR_BUFFER_BIT);
  glBegin(GL_TRIANGLES);
    glColor3f(1.0f, 0.0f, 0.0f);
    glVertex2f(0.0,  0.8);
    glColor3f(0.0f, 1.0f, 0.0f);
    glVertex2f(-0.8, -0.8);
    glColor3f(0.0f, 0.0f, 1.0f);
    glVertex2f(0.8, -0.8);
  glEnd();
  glFlush();
}


// Minimale windows interface

#define WIN_CLASS_NAME "MyGraphClass"

// Forward declarations

LONG WINAPI WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
HWND CreateOpenGLWindow(HINSTANCE hInstance,char* title, int x, int y, 
                        int width, int height, BYTE type, DWORD flags);


// Minimal Win32 main function

int APIENTRY WinMain(HINSTANCE hCurrentInst,HINSTANCE hPreviousInst,LPSTR lpszCmd,int nCmdShow)
{
HDC   hDC;	/* device context */
HGLRC hRC;	/* opengl context */
HWND  hWnd;
MSG   msg;
BOOL  quit = FALSE;

  hWnd = CreateOpenGLWindow(hCurrentInst,"Mini OpenGl Demo", 0, 0, 400, 400, PFD_TYPE_RGBA, 0);
  if (hWnd == NULL)
    exit(1);
  hDC = GetDC(hWnd);
  hRC = wglCreateContext(hDC);
  wglMakeCurrent(hDC, hRC);
  ShowWindow(hWnd, nCmdShow);
  // Windows message loop 
  while (!quit) {
    if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
      if (msg.message == WM_QUIT) {
        quit = TRUE;
      } 
      else {
        TranslateMessage( &msg );
        DispatchMessage( &msg );
      }
    }  
  }
  wglMakeCurrent(NULL, NULL);
  ReleaseDC(hWnd,hDC);
  wglDeleteContext(hRC);
  DestroyWindow(hWnd);
  return msg.wParam;
}

HWND CreateOpenGLWindow(HINSTANCE hInstance,char* title, int x, int y, 
                        int width, int height, BYTE type, DWORD flags)
{
int         pf;
HDC         hDC;
HWND        hWnd;
WNDCLASS    wc;
PIXELFORMATDESCRIPTOR pfd;

  wc.style         = CS_OWNDC;
  wc.lpfnWndProc   = (WNDPROC)WindowProc;
  wc.cbClsExtra    = 0;
  wc.cbWndExtra    = 0;
  wc.hInstance     = hInstance;
  wc.hIcon         = LoadIcon(NULL, IDI_WINLOGO);
  wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
  wc.hbrBackground = NULL;
  wc.lpszMenuName  = NULL;
  wc.lpszClassName = WIN_CLASS_NAME; 

  if (!RegisterClass(&wc)) {
    MessageBox(NULL, "RegisterClass() failed!", "Error", MB_OK);
    return NULL;
  }
  hWnd = CreateWindow(WIN_CLASS_NAME, title, 
    WS_OVERLAPPEDWINDOW | WS_CLIPSIBLINGS | WS_CLIPCHILDREN, 
    x, y, width, height, NULL, NULL, hInstance, NULL);
  if (hWnd == NULL) {
    MessageBox(NULL, "CreateWindow() failed!","Error", MB_OK);
    return NULL;
  }
  hDC = GetDC(hWnd);
  memset(&pfd, 0, sizeof(pfd));
  pfd.nSize        = sizeof(pfd);
  pfd.nVersion     = 1;
  pfd.dwFlags      = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | flags;
  pfd.iPixelType   = type;
  pfd.cColorBits   = 32;
  pf = ChoosePixelFormat(hDC, &pfd);
  if (pf == 0) {
    MessageBox(NULL, "ChoosePixelFormat() failed!","Error", MB_OK); 
    return NULL;
  } 
  if (SetPixelFormat(hDC, pf, &pfd) == FALSE) {
    MessageBox(NULL, "SetPixelFormat() failed!","Error", MB_OK);
    return NULL;
  } 
  DescribePixelFormat(hDC, pf, sizeof(PIXELFORMATDESCRIPTOR), &pfd);
  ReleaseDC(hWnd,hDC);
  return hWnd;
}    

// Minimal windows proc handler

LONG WINAPI WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{ 
static PAINTSTRUCT ps;

  switch(uMsg) {
    case WM_PAINT:
      display();
      BeginPaint(hWnd, &ps);
      EndPaint(hWnd, &ps);
      return 0L;
    case WM_SIZE:
      glViewport(0, 0, LOWORD(lParam), HIWORD(lParam));
      PostMessage(hWnd, WM_PAINT, 0, 0);
      return 0L;
    case WM_CHAR:
      switch (wParam) {
      case 27:			/* ESC */
        PostQuitMessage(0);
        break;
      }
      return 0L;
    case WM_CLOSE:
      PostQuitMessage( 0 );
      return 0;
  }
  return DefWindowProc(hWnd, uMsg, wParam, lParam); 
}