Introduction to Windows Programming and OpenGL:

#include  int APIENTRY WinMain(HINSTANCE hInstance,                      HINSTANCE hPrevInstance,                      LPSTR     lpCmdLine,                      int       nCmdShow) {     MessageBox(NULL, "\tHello World!", "My first windows app", NULL);  return 0; }

Every Windows programming needs a main entry point. That being said, you may be wondering what this entry point is. The main entry point for any Windows program is called WinMain. The function prototype for WinMain is a little confusing at first, but as we continue to work with it you'll notice it becomes much easier to understand. Well. we've told you what it is; now were going to show you! Here's the prototype for WinMain:

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd);

hInstance - is a handle to your applications instance, where an instance  can be considered to be a single run of your application. The instance  is used by windows as a reference to your application for event handling, message processing, and various other duties. hPrevInstance - is always NULL.  lpCmdLine - is a pointer string that is used to hold any command-line arguments that may have been specified when the application began.   For example, if the user opened the Run application and typed myapp.exe myparameter 1, then lpCmdLine would be myparameter 1. nShowCMD - is the parameter that determines how your application's window will be displayed once it begins executing. 

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam); 

hwnd - Only important if you have several windows of the same class open at one time. This is used to determine which window hwnd pointed to before  deciding on an action. message - The actual message identifier that WndProc will be handling. wParam and lParam - Extensions of the message parameter. Used to give  more information and point to specifics that message cannot on its own. 

First Windows Application:

/* Trim fat from windows*/ #define WIN32_LEAN_AND_MEAN  #pragma comment(linker, "/subsystem:windows") /* Pre-processor directives*/ #include "stdafx.h" #include  /* Windows Procedure Event Handler*/ LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {  PAINTSTRUCT paintStruct;  /* Device Context*/  HDC hDC;   /* Text for display*/  char string[] = "Hello, World!";   /* Switch message, condition that is met will execute*/  switch(message)  {   /* Window is being created*/   case WM_CREATE:     return 0;    break;   /* Window is closing*/   case WM_CLOSE:     PostQuitMessage(0);    return 0;    break;   /* Window needs update*/   case WM_PAINT:     hDC = BeginPaint(hwnd,&paintStruct);    /* Set txt color to blue*/    SetTextColor(hDC, COLORREF(0x00FF0000));    /* Display text in middle of window*/    TextOut(hDC,150,150,string,sizeof(string)-1);    EndPaint(hwnd, &paintStruct);    return 0;    break;   default:    break;  }  return (DefWindowProc(hwnd,message,wParam,lParam)); } /* Main function*/ int APIENTRY WinMain(HINSTANCE hInstance,                      HINSTANCE hPrevInstance,                      LPSTR     lpCmdLine,                      int       nCmdShow) {  WNDCLASSEX  windowClass;  //window class  HWND  hwnd;    //window handle  MSG   msg;    //message  bool  done;    //flag saying when app is complete  /* Fill out the window class structure*/  windowClass.cbSize = sizeof(WNDCLASSEX);  windowClass.style = CS_HREDRAW | CS_VREDRAW;  windowClass.lpfnWndProc = WndProc;  windowClass.cbClsExtra = 0;  windowClass.cbWndExtra = 0;  windowClass.hInstance = hInstance;  windowClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);  windowClass.hCursor = LoadCursor(NULL, IDC_ARROW);  windowClass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);  windowClass.lpszMenuName = NULL;  windowClass.lpszClassName = "MyClass";  windowClass.hIconSm = LoadIcon(NULL, IDI_WINLOGO);  /* Register window class*/  if (!RegisterClassEx(&windowClass))  {   return 0;  }  /* Class registerd, so now create window*/  hwnd = CreateWindowEx(NULL,  //extended style   "MyClass",   //class name   "A Real Win App",  //app name   WS_OVERLAPPEDWINDOW |  //window style   WS_VISIBLE |   WS_SYSMENU,   100,100,   //x/y coords   400,400,   //width,height   NULL,    //handle to parent   NULL,    //handle to menu   hInstance,   //application instance   NULL);    //no extra parameter's  /* Check if window creation failed*/  if (!hwnd)   return 0;  done = false; //initialize loop condition variable  /* main message loop*/  while(!done)  {   PeekMessage(&msg,NULL,NULL,NULL,PM_REMOVE);   if (msg.message == WM_QUIT) //check for a quit message   {    done = true; //if found, quit app   }   else   {    /* Translate and dispatch to event queue*/    TranslateMessage(&msg);     DispatchMessage(&msg);   }  }  return msg.wParam; } 

HDC hDC;    //device context Char string[] = "Hello World!"; //display text 

case WM_PAINT:     hDC = BeginPaint(hwnd,&paintStruct);    /* Set txt color to blue*/    SetTextColor(hDC, COLORREF(0x00FF0000));    /* Display text in middle of window*/    TextOut(hDC,150,150,string,sizeof(string)-1);    EndPaint(hwnd, &paintStruct);    return 0;    break; 

1. Window-class setup 2. Window-class registration 3. Window Creation 4. Message loop with event handler 

WGL and the Wiggle Functions in C++:

• wglCreateContext();
• wglDeleteContext();
• wglMakeCurrent();

 HGLRC wglCreateContext(HDC hDC); 

 BOOL  wglDeleteContext(HGLRC hRC); 

 BOOL  wglMakeCurrent(HDC hDC, HGLRC hRC); 

LRESULT CALLBACK WndProc (HWND hwnd, UNIT message, WPARAM wParam, LPARAM lParam) {  static HGLRC hRC; //rendering context  static HDC hDC; //device context  switch (message)  {  case WM_CREATE:  hDC = GetDC(hwnd); //get the device context for window  hRC = wglCreateContext(hDC); //create rendering context  wglMakeCurrent(hDC,hRC); //make rendering context current  break;  case WM_DESTROY:  wglMakeCurrent(hDC,NULL); //deselect rendering context  wglDeleteContext(hRC);  //delete rendering context  PostQuitMessage(0);  //send wm_quit  break;  } }