//////////////////////////////////////////
// //
// SIMPLEST WINDOWS PROGRAM //
// //
// You found this at bobobobo's weblog, //
// http://bobobobo.wordpress.com //
// //
// Creation date: Jan 31/08 //
// Last modified: Feb 9/08 //
// //
//////////////////////////////////////////
#include <windows.h>
// Function prototypes.
LRESULT CALLBACK WndProc( HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam );
int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR szCmdLine, int iCmdShow );
////////////////////////////
// Introduction:
// Basic Windows Program!
//
// This package demonstrates how to build a very basic Windows application
// on a Win O/S system from Windows 3.1 to Windows XP using C++ code.
//
// * Prerequisites to understanding this program:
// - Already understand how to create Console applications in C++.
// - Full understanding of C FUNCTIONS, FUNCTION PARAMETERS/ARGUMENTS.
//
// If you don't know what those are, go learn what
// they are before going on reading this!
//
///////////////////
// OVERVIEW:
// Windows applications in C++ are easy!
// To understand them, you must first see the big
// picture. Then you can get your hands dirty
// and get right into the code.
///////////////////
// Big picture.
//
// Windows apps are much different than console apps.
// A console app, (which you probably are used to)
// has just a single "main" function called main().
// Every Windows app has __2__ functions that are very
// important to it.
// These 2 functions are WinMain and WndProc. WinMain
// and WndProc really form the Windows' app's heart and soul.
//
// A. WinMain: Application STARTING POINT. REPLACES
// main() function that you might be used to
// from regular C/C++ programs.
//
// B. WndProc: A function that PROCESSES MESSAGES from
// the Windows O/S as they come in.
//
///////////////////
// BUT what's a MESSAGE???
//
// The idea of "messages" takes some getting used
// to, but it is really a simple concept.
//
// The Windows Operating system is like a GOVERNMENT.
//
// All of the little windows that live inside
// (the Firefox window, the MSWord window,
// and YOUR PROGRAM's window!) are people owned
// by the Windows GOVERNMENT.
//
// So, whenever the user attempts to interact
// with ANY program window inside that Windows Government,
// either by clicking on your window, or by pressing a key
// while your program has the "input focus" (when
// your window is "selected"),
// the Windows O/S INTERCEPTS that communication FIRST.
//
// THEN, a fraction of a second later, (almost
// instantly), the Windows O/S SENDS A a "MESSAGE"
// to YOUR Window program that "HEY! THE USER
// CLICKED ON YOU AT LOCATION (22, 405), USING
// THE RIGHT MOUSE BUTTON." or "HEY! THE
// USER PRESSED THE 'A' KEY, AND HE WAS ALSO HOLDING
// DOWN SHIFT WHILE HE PRESSED IT."
// THAT is what a MESSAGE is. Its a notification
// from the Windows O/S that the user has
// done something to your program's window.
// ONCE your program receives this
// "MESSAGE", your program can THEN execute some code
// in response to that particular MESSAGE.
// The WndProc function will contain ALL of
// your "MESSAGE HANDLING CODE" -- that is,
// the code pieces that you want executed
// when certain window events happen.
// This is called EVENT DRIVEN PROGRAMMING.
// And in most standard Windows applications, this is
// how things happen.
// Most of a basic, standard Windows application's
// time is spent WAITING for events.
// And that is what a message is!
//////////////////////////////
// OF INSTANCES AND HANDLES.
//
// There are 2 concepts you must understand intuitively first
// before diving into Windows programming.
// Those concepts are the concept of an INSTANCE,
// and the concept of a HANDLE.
///////////////
// INSTANCES:
// The first concept is the concept of an INSTANCE of a program.
// What's an INSTANCE?
// An INSTANCE of an application is just one running OCCURRENCE of it.
// If you open up 3 different NOTEPAD.exe windows, then you have
// created __3__ different, separate INSTANCE of the NOTEPAD program
// inside your Windows Kernel.
// If you're familiar with OOP, an easy explanation is this:
// PROGRAM CODE >> like a C++ class definition.
// ACTUALLY RUNNING PROGRAM CODE >> like an "instance" of the class, this is an INSTANCE of the program.
///////////////
// HANDLES:
// HANDLES pop up EVERYWHERE in Windows programming (and all other
// types of programming as well!) So I'm hoping to explain the idea
// behind a HANDLE intuitively, so that you have something to "hold onto"
// whenever you see use of HANDLES in program code.
// Think about a POT of boiling water. Inside that pot is
// some corn on the cob being cooked.
// Now, say you want to ACCESS the pot, so you can dump its
// contents out into the sink and drain the corn.
// How do you do that? Do you GRAB THE POT DIRECTLY??? NO!!
// That would be stupid. Instead, you grab the HANDLE TO THE POT.
// Using the HANDLE to the pot, you manipulate the pot, slowly
// dumping out the water and leaving the corn behind. Then you
// eat the corn and it is delicious.
// Now, in programming, the idea of a HANDLE is much the same.
// A HANDLE to a WINDOW is __NOT__ the window itself in an application
// variable. Instead, it is a POINTER TO, A REFERENCE TO the
// window itself.
// A HANDLE TO AN INSTANCE in an application variable is NOT
// the application INSTANCE itself. Rather, it is a POINTER TO
// that application instance. The application instance exists
// somewhere in the Windows O/S's program memory. You use the
// programmatic HANDLE that you have as YOUR MEANS TO MANIPULATE
// AND DEAL WITH that application instance.
// The benefits of HANDLES are many! You'll see as we go on.
// Onto WinMain()!
////////////////////////////
// In a C++ Windows app, the starting point is WinMain().
int WINAPI WinMain( HINSTANCE hInstance, // HANDLE TO AN INSTANCE. This is the "handle" to YOUR PROGRAM ITSELF. More in the GLOSSARY at the bottom.
HINSTANCE hPrevInstance,// USELESS on modern windows (totally ignore hPrevInstance)
LPSTR szCmdLine, // Command line arguments. Explained near BOTTOM of this file.
int iCmdShow ) // Start window maximized, minimized, etc.
{
// As we said before, WinMain is the application starting point.
// A: WinMain does 2 main things:
// 1. STARTUP STUFF: CREATE THE WINDOW ITSELF, AND LOAD IT UP
// SO IT APPEARS ON THE SCREEN.
//
// 2. KEEP CHECKING WITH WINDOWS O/S TO SEE IF THE USER
// HAS INTERACTED WITH THE APPLICATION ("MESSAGE LOOP")
// If the user has clicked on anything, or pressed any keys while
// our window is ACTIVE (our window has the "input focus")
// then we are to DISPATCH a MESSAGE to WndProc (make
// a function call to WndProc) that tells
// WndProc EXACTLY what the user did to our window (clicked?
// key pressed?), when it happened, etc. WndProc then
// has the opportunity to EXECUTE SOME CODE in response
// to that particular user interaction.
#pragma region part 1 - STARTUP STUFF
// A. Create WNDCLASS structure and initialize it
// The WNDCLASS structure tells Windows WHAT KIND OF
// WINDOW we dream of creating.
// A note: Use the TEXT() macro whenever you have a
// string value that gets passed to a Windows
// function. Its good and makes life easier.
WNDCLASS wc;
wc.cbClsExtra = 0; // ignore for now
wc.cbWndExtra = 0; // ignore for now
wc.hbrBackground = (HBRUSH)GetStockObject( WHITE_BRUSH ); // I want the window to have a white background
wc.hCursor = LoadCursor( NULL, IDC_ARROW ); // I want it to have an arrow for a cursor
wc.hIcon = LoadIcon( NULL, IDI_APPLICATION ); // I want it to have that envelope like icon
wc.hInstance = hInstance; // INSTANCE HANDLE -- see the GLOSSARY PART of this file for an explanation of what HINSTANCE is
wc.lpfnWndProc = WndProc; // Give name of WndProc function here.
wc.lpszClassName = TEXT("Philip"); // I have named it Philip.
// You could name it anything
// you want, but you have to
// remember the name for when
// you call CreateWindow().
wc.lpszMenuName = 0; // no menu - ignore
wc.style = CS_HREDRAW | CS_VREDRAW; // Redraw the window
// on BOTH horizontal resizes (CS_HREDRAW) and
// vertical resizes (CS_VREDRAW). There are
// many more window class styles!
// B. Register the WNDCLASS with Windows, THEN
// create the window.
RegisterClass( &wc ); // This kind of "plants" the information
// about the Window we "dream"
// of creating somewhere inside the Windows O/S...
// NOW, at this next stage, WE ACTUALLY CREATE
// the window. The previous lines of code
// until this point have only been PREPARATION.
// When we call the CreateWindow() function, we will
// make a reference to this WNDCLASS structure (BY ITS
// NAME -- "Philip"), and the Windows government
// will grant us our wish and a REAL LIVE WINDOW,
// with the properties that we specified in the
// WNDCLASS structure!
// NOTICE that the value that is returned from
// CreateWindow is a variable of type HWND.
// HWND is a "handle to a window" - its a programmatic
// reference variable to the Window.
// The HWND is OUR MEANS BY WHICH to manipulate
// our Window.
// Read the schpeal near the top of this file if
// not sure about HANDLES.
// Most of the time, you would want to save
// this HWND into a global variable,
// so you wouldn't lose it later.
HWND hwnd = CreateWindow(
TEXT("Philip"), // THIS IS THE LINK
// to the WNDCLASS structure that
// we created earlier.
TEXT("window's title!"),// appears in title of window
WS_OVERLAPPEDWINDOW, // STYLE of window. WS_OVERLAPPEDWINDOW just means
// the window we create should have a few common features
// like a minimize box, a maximize box, and it should
// be resizeable by dragging the "thick frame" around
// the window. There are other styles
// and they all start with WS_. Check it out in the
// autocomplete by typing WS_ THEN PRESSING CTRL+SPACE
// to make the autocomplete window come up.
10, 10, // x, y start coordinates of window
200, 200, // width, height of window
NULL, NULL, // nothing and nothing (ignore to start out)
hInstance, NULL ); // hInstance -- (see glossary), nothing
// Next, SHOW and PAINT the window!
// You won't see the window if you DO NOT
// call ShowWindow();
ShowWindow(hwnd, iCmdShow );
UpdateWindow(hwnd);
#pragma endregion
#pragma region part 2 - ENTER A LOOP TO CONTINUALLY KEEP CHECKING WITH WIN O/S FOR USER INTERACTION
// first, we create the MSG structure.
MSG msg;
// But WTF IS A MESSAGE???
// A MESSAGE is something that the Windows O/S
// SENDS your application program when
// SOMETHING HAPPENS TO YOUR WINDOW.
// Messages can be anything from "the user
// has moved your window", to "the user
// has clicked at pixel location (20, 20)" or,
// "you need to paint yourself", or,
// "you have been maximized".
// YOUR CHANCE to handle those "messages"
// that get passed to your window comes
// IN WNDPROC.
while( GetMessage( &msg, NULL, 0, 0 ) )
{
// GetMessage is a function that will not
// return until the Windows O/S HAS A message
// for our program.
// Since the GetMessage() function call is
// INSIDE the bracket for the while Loop,
// this means that our program is essentially
// "put on hold" or halted until the GetMessage function
// returns.
// If and when the user interacts with our
// application's window, then the GetMessage()
// function WILL return and the variable
// msg will be filled with interesting details
// about exactly what the user did to the window.
TranslateMessage( &msg ); // translates
// the message so WndProc can process it
// more easily.
// Next we 'dispatch' the message, or
// send it off to WndProc for processing.
// Notice that there is NO EXPLICIT function
// call to WndProc, but somehow in the bowels
// of the Windows O/S, calling DispatchMessage
// WILL result in a call to your WndProc function,
// WITH the appropriate msg struct passed in
// as well.
DispatchMessage( &msg ); // this line RESULTS IN
// a call to WndProc(), passing the message and
// the HWND.
}
#pragma endregion
return msg.wParam; // return from WinMain
}
LRESULT CALLBACK WndProc( HWND hwnd, // "handle" to the window that this message is for
UINT message, // TYPE of message (e.g. WM_PAINT is a message asking to paint the window)
WPARAM wparam, // information about the actual message
LPARAM lparam ) // MORE info about the message
{
// If WinMain was the heart of the Windows application, then
// WndProc is the soul.
// WndProc does just 1 thing:
// - Execute some bit of code in response
// to user interactions with our windows
// application.
// The tricky bit about WndProc is that NOWHERE IN THIS APP'S
// CODE DO YOU EVER SEE ANY EXPLICIT FUNCTION CALLS
// TO WndProc!!! Does that mean WndProc never
// gets used???
// NO!!! Take a look again, around where
// we create the WNDCLASS.
// Notice, how the WNDCLASS has lpfnWndProc = WndProc??
// THAT is the reference to this function.
// The WINDOWS O/S PERFORMS the function call to
// WndProc when we call DispatchMessage().
switch( message )
{
case WM_CREATE:
// upon creation, let the speaker beep at 50Hz, for 10ms.
Beep( 50, 10 );
return 0;
break;
case WM_PAINT:
{
// we would place our Windows painting code here.
HDC hdc;
PAINTSTRUCT ps;
hdc = BeginPaint( hwnd, &ps );
// draw a circle and a 2 squares
Ellipse( hdc, 20, 20, 160, 160 );
Rectangle( hdc, 50, 50, 90, 90 );
Rectangle( hdc, 100, 50, 140, 90 );
EndPaint( hwnd, &ps );
}
return 0;
break;
case WM_DESTROY:
PostQuitMessage( 0 ) ;
return 0;
break;
}
// Now, try going into Visual Studio and
// press WM_ then press CTRL + SPACE.
// Or go to
// http://msdn2.microsoft.com/en-us/library/ms632595.aspx
// See that huge listing? Those are ALL THE EVENTS
// that Windows could possibly throw at our application.
// WOW! That's a lot of events. WE don't want to
// have to write code for every single one of them!
// But our WndProc gets called whenever ANY event
// happens to our application. What do we do with
// the events we don't want to handle?
// Simple. We will pass the events we DON'T want
// to handle to DefWindowProc(). DefWindowProc()
// knows what to do with the events we don't want
// to handle so that our application remains stable
// and good.
return DefWindowProc( hwnd, message, wparam, lparam );
}
/// GLOSSARY ///
// HINSTANCE: "Handle" to an instance. Every running INSTANCE
// of an application has a handle to it that is YOUR MEANS
// by which to manipulate, talk about, or refer to that specific
// application instance as it exists inside the Windows O/S.
// What's an instance again? If you have 2 copies of the same programming running
// at the same time, then you are running 2 INSTANCES
// of the same program (2 copies of Microsoft Word, for example).
// Each INSTANCE of a program has its own INSTANCE HANDLE and
// hence its PID (ProcessID - unique integer identifier
// for each program that is currently running in the Windows O/S)
// and its own entry in the Window task manager.
// TRY THIS: Press CTRL+ALT+DEL to bring up the Windows
// Task Manager.
// Now switch to the PROCESSES tab.
// Click the "IMAGE NAME" column, so that everything gets organized by name of the process.
// Now, open NOTEPAD, 3 times. You should have 3 Notepad windows open.
// NOW, LOOK AT the Windows Task Manager. Try to locate __3__ entries
// that say NOTEPAD.EXE. Open a fourth notepad. Open a fifth notepad.
// every instance of notepad you open gets its own entry in that table.
// Now HINSTANCE is exactly what it sounds like . . its a "handle"
// (a means by which to access or control) the INSTANCE of your
// program.
//
// The actual INSTANCE of your application lives inside the Windows O/S.
// But you have a HANDLE TO IT, and your HANDLE to it is your means
// by which to manipulate it, refer to it, change it, or delete it.
// HWND: HANDLE TO A WINDOW. This is exactly the same in CONCEPT as
// the INSTANCE HANDLE, but now, this is a handle TO THE WINDOW ITSELF.
// The HANDLE TO THE WINDOW is your means by which to change
// manipulate, or refer to the window that belongs to your program.
// A single INSTANCE of an application can have MULTIPLE window
// handles associated with it. THAT IS WHY when you CREATE A WINDOW,
// using the CreateWindow() function, you MUST PASS the hInstance
// parameter. That is so that Windows knows which application
// INSTANCE is attached to which WINDOW.
//
// HDC: HANDLE TO A DEVICE CONTEXT. Hmm. I'm not going to explain this
// in detail here, because we're not really using the HDC much
// in this example. Perhaps at a later time.
///////////////////////////
// THERE, ALL DONE - CLOSING NOTES.
// Everyone knows starting Windows Programming can be a bit hard.
// There are a few things I'd like to highlight here.
//
// Now you might be wondering, "ok, if WinMain is the application
// starting point, WHERE / WHEN / HOW does WinMain accept
// PARAMETERS?"
//
// To understand this, you must start to see your "Windows program"
// as really just a FUNCTION that Windows will call, when it is
// time to start up your application.
//
// So where do the values of hInstance, hPrevInstance, szCmdLine
// and iCmdShow come from?
// These parameters are PASSED BY the Windows O/S AT APPLICATION START TIME.
// So all of hInstance, hPrevInstance (which is always passed as NULL)
// szCmdLine and iCmdShow are passed by the Windows O/S
// to your application.
////////////////////
// Understanding what szCmdLine is and does:
//
// Do me a favor.
// Open the Windows command prompt (go to START->Run,
// then type "cmd" in the box that appears there.)
//
// You should see a black console window, like the one that your basic console C++
// apps run in. In the black window, type in:
// explorer
// then press enter.
// What should happen is your windows file explorer should pop up.
// Now go back to the command prompt and type in
// explorer "C:\Program Files"
// Notice now that the Windows disk explorer now opens in the folder "C:\Program Files"
// In the above example, "C:\Program Files" is a command line argument that modifies
// the behaviour of the disk explorer upon its launch.
// So the explorer.exe program is a Windows program.
// And szCmdLine WOULD BE WHERE YOU TAKE that extra string
// that is passed to the program at the time the program is
// launched.
// You won't necessarily use this at all in your programming!
// But, it is good to know.
// REFERENCES:
// If you want to know more about Windows Programming
// in this CLASSIC C++ way, then you should pick
// up a copy of Charles Petzold's "Programming Windows,
// 5th Edition"
// http://www.charlespetzold.com/pw5/
// On Amazon: http://www.amazon.com/exec/obidos/ISBN=157231995X
// "The Petzold" is THE reference that all the game
// books out there (some of which are pretty good!)
// draw on when they write their Win32 chapter (its
// obvious from the way they've written them!)
// What's annoying is, a lot of the people who write
// those books though, never acknowledge Petzold or
// mention where they derived their Win32 understanding
// from.
// So, the Petzold is where I got my initial understanding
// anyway, and its really good. Check it out
// from your library if you haven't the $.
// More refs:
// MSDN: "About messages and message queues"
// http://msdn2.microsoft.com/en-us/library/ms644927(VS.85).aspx
////////////////
// MORE Closing notes:
// This is sometimes called "EVENT DRIVEN
// PROGRAMMING" -- the idea is that your
// program is entirely driven by EVENTS.
// If there are no events, then your
// Windows program DOES NOTHING.
// Note that this is NOT the case with GAMES!
// GAMES CAN'T WAIT! Games must be fast.
// For games, you would use DirectInput,
// and things like that, and you WOULD NOT
// be WAITING for messages. Instead,
// you want to be DIRECTLY listening
// at the keyboard and mouse for user
// interaction with those DEVICES.
///////////////////
// You MIGHT HAVE been wondering about
// the apparent RETURN TYPE of WinMain and
// WndProc.
// Looking at those function prototypes, we have:
/*
int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR szCmdLine, int iCmdShow );
LRESULT CALLBACK WndProc( HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam );
*/
// For example, a question you might have might be:
// WHY is the return type of WinMain "int WINAPI"?
// That is so weird.
// The short answer, is ITS NOT!!
// The return type of WinMain is just INT.
// "WINAPI" IS NOT PART OF THE RETURN TYPE
// OF THE WinMain FUNCTION!
// The second word after the return type
// (WINAPI) is called the CALLING CONVENTION of
// the function.
// In case you're still interested, check out
// these links:
// http://support.microsoft.com/kb/100832
// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/html/_core_calling_conventions_topics.asp
// http://www.devnewz.com/devnewz-3-20050125UsingWin32CallingConventions.html
// A MSDN basic window example:
// http://msdn2.microsoft.com/en-us/library/aa383668(VS.85).aspx
// MSDN root page for a lot of windows stuff
// http://msdn2.microsoft.com/en-us/library/ms632586(VS.85).aspx
/*
____ __ __ __ __ ___
/ _ \ / / / / / / \ \/ /
/ _/ / / / / / / / \ /
/ _/ \ / / / /__ / /__ / /
/_____//__/ /______//______/ /__/
*/
Check out the Visual Studio project files [updated Feb 9 / 08] hosted by esnips! (Thanks esnips!)
