Win32

event driven
1. when events happen, they stored into message form
2. message stored into system queue
3. OS was checking for system queue
4. OS send message to aplication’s thread message queue
5. application was checking for thread message queue (GetMessage)
6. application calls event-matching callback function (TranslateMessage, DispatchMessage)
creating window
1. declare WNDCLASS object
2. declare proper LRESULT CALLBACK (*callback_function) (HWND, UINT, WPARAM, LPARAM)
3. change fields(properties) inside WNDCLASS object
  - you need to set ipfnWndProc into callback_function as window processor
  - you need to set lpszClassName into LPCSTR type string as window class name
4. declare WNDCLASS object with RegisterClass()
5. Create window with CreateWindow()
  - you need to call ShowWindow() if window is invisible
window programming
- SDK (Software Development Kit) : low level programming with winAPI
- MFC (Microsoft Foundation Class) : useful library constructed by SDK
- RAD (Rapid Application Development) : faster and easier than MFC
handle
- index, object, instance, name, pointer, address
- 32bit integer
- start with h~
- HWND, HPEN, HBRUSH, HDC
prefix
- h~ : handle
- n~ : (?)
- l~ : unicode (long)
data type
- BOOL
- BYTE : 8 bit unsigned
- DWORD : 32 bit unsigned
- LONG : 32 bit signed (same with long)
- LONGLONG : 64 bit unsigned
- FLOAT : float
- LPARAM : same with LONG but used for message parameter (32 bit)
- LPSTR : editable string. char * type pointer. end with NULL
- LPCSTR : uneditable string. const char * type pointer . end with NULL (const LPSTR)
- LPTSTR : editable unicode string. TCHAR * type pointer. end with NULL
- LPCTSTR : uneditable unicode string. const TCHAR * type pointer. end with NULL (const LPTSTR)
- TCHAR : unicode (window character)
- UNIT : 32 bit unsigned
- WORD : 16 bit unsigned
- WPARAM : same with UINT but used for message parameter (16 bit)
- COLORREF : composition of R, G, B (32 bit integer)
- POSITION : pointer for list attribute
- HWND : handle. 32 bit, same with HPEN, HHBRUSH, HDC
OutputDebugString()
```
void OutputDebugString( LPCTSTR );
```
print debug messages while debugging window program

tbu
- WinMain()
```
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpszCmdParam, int nCmdShow);
```
  main() of Window programming (entry point)
  - hInstance : current instance of application
  - hPrevInstance : deplicated. (used on 32-bit Windows)
  - lpCmdLine : pointer for cmd parameters
  - nCmdShow : choose how window will be seen on screen (NULL for default)
  make window class.
  register window class.
  create window.
  show window.
  do get-message loop.
  return (end) program if loop is ended.
- WNDCLASS
```
typedef struct tagWNDCLASS
{
    UINT		style;
    WNDPROC		ipfnWndProc;
    int		cbClsExtra;
    int		cbWndExtra;
    HINSTANCE	hInstance;
    HICON		hIcon;
    HCURSOR		hCursor;
    HBRUSH		hbrBackground;
    LPCSTR		lpszMenuName;
    LPCSTR		lpszClassName;
} WNDCLASS;
```
  make window class with meta-class
  - lpfnWndProc : ESSENTIAL. window processor (callback funtion to bind)
  - lpszClassName : ESSENTIAL. window class
  - cbClsExtra, cdWndExtra : extra class memory, extra window memory (?)
  - hInstance : current application instance handle (use already-made instance handle)
  - hIcon, hCursor : handle for Icon and Cursor (use LoadCursor(), LoadIcon())
  - hbrBackground : brush for background (use GetStockObject())
  - lpszMenuName : (?)
  - style : what can user change with window (?)
- RegisterClass()
```
void RegisterClass (WNDCLASS* WndClass);
```
  register window class with this function
- CreateWindow()
```
HWND CreateWindow ( lpszClassName, lpszWindowName, dwStyle, x, y, nWidth, nHeight, hWndParent, hMenu. hInst, lpvParam );
```
  create window with registered window class
  returns handle
  - lpszClassName : window class
  - lpszWindowName : window’s name that will be shown on title bar
  - dwStyle : the way how windows will be shown (?)
  - x, y, nWidth, nHeight : location and size of window
  - hWndParent : parent window’s handle (?)
  - hMenu : control’s handle
  - hInst : current application instance’s handle
  - hpvParam : extra parameter (?)
```
#define WS_OVERLAPPEDWINDOW \
	(WS_OVERLAPPED 	|\
		 WS_CAPTION 	|\
		 WS_SYSMENU	|\
		 WS_THICKFRAME	|\
		 WS_MINIMIZEBOX	|\
		 WS_MAXIMIZEBOX)
```
  WS_VISIBLE make you can skip ShowWindow() in some cases.
- ShowWindow()
```
void ShowWindow (hWnd, nCmdShow);
```
  show created window instance on screen
  - hWnd
  - nCmdShow
    - SW_HIDE : hide window (not minimize)
    - SW_MINIMIZE : minimize window and not activate (inactive state) it
    - SW_RESTORE : show window on screen (remember window posision and size when do min/max)
    - SW_SHOW : show window on screen (?)
    - SW_SHOWNORMAL : show window on screen (?)
- GetMessage()
```
BOOL GetMessage ( LPMSG lpMsg, HWND hWnd, UINT wMsgFilterMin, UINT wMsgFilterMax );
    //TranslateMessage( &Message );
    //DispatchMessage( &Message );
```
  get message from queue
  returns bool
  returns false when message is WM_QUIT to finish event loop
  - lpMsg : MSG structure’s pointer
  - hWnd : message destination window’s handle. (search every message if hWnd is NULL)
  - wMsgFilterMin, wMsgFilterMax : message range to search. (search every message if they are 0)
- event example
  - WM_QUIT : occur when user end program
  - WM_LBUTTONDOWN : occur when mouse left button clicked
  - WM_CHAR : occur when keyboard character inputed
  - WM_PAINT : occur when screen need to be drawn again
  - WM_DESTROY : occur when window deleted inside memory (normally occur WM_QUIT at the end to stop loop)
  - WM_CREATE : occur when window is created (normally create child windows when this occur)
- message struct
```
typedef struct tagMSG
{
    HWND	hwnd;	//window handle
    UINT	message;	//message
    WPARAM	wParam;	//window id
    LPARAM	lParam;	
    DWORD	time;	//time when event occur
    POINT	pt;	//mouse position
} MSG;
```
- TranslateMessage()
```
BOOL TranslateMessage ( CONST MSG* lpMsg );
```
  translate event message into WM_CHAR type
  returns bool
  - lpMsg
- DispatchMessage
```
LONG DispatchMessage ( CONST MSG* lpMsg );
```
  dispatch message to operating system to call window processor
  - lpMsg
- PeekMessage()
```
BOOL PeekMessage( LPMSG lpMsg, HWND hWnd, UINT wMsgFilterMin, UINT wMsgFilterMax, UINT wRemoveMsg );
```
  return TRUE if found message
  return FALSE if couldn’t find message
  - almost same with GetMessage, but different in read message disposal
  - wRemoveMsg :
    - PM_REMOVE : remove message in queue
    - PM_NOREMOVE : let message stay in queue
- SendMessage()
```
LResult SendMessage( HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam );
```
  send message directly to message processor (not passing message queue)
- PostMessage()
```
LResult PostMessage( HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam );
```
  post message on message queue

WndProc()

LRESULT CALLBACK WndProc (HWND hWnd, UINT iMessage, WPARAM wParam, LPARAM lParam)
{
    LPCTSTR text = L"window text example";

    switch ( iMessage )
    {
        case WM_PAINT:
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint( hWnd, &ps );	//hdc == handle device context

            TextOut( hdc, 10, 10, text, lstrlen(text) );
            EndPaint( hWnd, &ps );
            return 0;

        // ... event cases ....

        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
    }
    return DefWindowProc( hWnd, iMessage, wParam, lParam );	// windows-default event processing
  }

every window own window processor one by one
WIndows will call with message to proper processor when event occurs
main mission of Window processor is dealing with event, message
and that makes callback function (window processor) do every job of window, even making child window

hWnd : window handle (return value of CreateWindow())
iMessage : event message
wParam : used for WM_COMMAND
lParam : used for WM_COMMAND