Chapter III, Windows and messages

Each window of the application has a window procedure function associated with it, and Windows passes the message to the window by invoking the window procedure. The window procedure handles the message accordingly, and then returns control to Windows.

The window class identifies the window procedure used to process messages passed to a window, allowing multiple windows to share the same window class.

Message Queuing holds messages for all windows that an application might create, and the message loop retrieves messages from the message queue and sends them to the appropriate window procedure.

#include <Windows.h>#include<mmsystem.h>#pragmaComment (lib, "WINMM. LIB ")LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM); HWND hwnd;intWINAPI WinMain (hinstance hinstance, hinstance hprevinstance, PSTR szCmdLine,inticmdshow) {    StaticTCHAR szappname[] = TEXT ("Hellowin");    MSG msg;    Wndclass Wndclass; Wndclass.style= Cs_hredraw |Cs_vredraw; Wndclass.lpfnwndproc=WndProc; Wndclass.cbclsextra=0; Wndclass.cbwndextra=0; Wndclass.hinstance=hinstance; Wndclass.hicon= LoadIcon (null,idi_application);//load icon for use by the programWndclass.hcursor = LoadCursor (NULL, Idc_arrow);//load the mouse cursor for use by the programWndclass.hbrbackground = (hbrush) getstockobject (White_brush);//gets a drawing object that is used in this example to redraw the background of a window. Wndclass.lpszclassname =Szappname; Wndclass.lpszmenuname=NULL; if(! RegisterClass (&wndclass))//Registering a window class for the application's window{MessageBox (NULL, TEXT ("This program requires Windows nt!"), Szappname, Mb_iconerror);//Show message Box        return 0; } hwnd=CreateWindow (Szappname, TEXT ("The Hello program"), Ws_overlappedwindow, Cw_usedefault, Cw_usedefa                        ULT, Cw_usedefault, Cw_usedefault, NULL,                                        NULL, HINSTANCE, NULL); //Create a window based on a window classShowWindow (hwnd, icmdshow); //displaying windows in the screenUpdateWindow (HWND);//instructs the window to redraw itself     while(GetMessage (&msg,null,0,0))//getting messages from Message Queuing{TranslateMessage (&AMP;MSG);//Translate some keyboard messagesDispatchMessage (&AMP;MSG);//send a message to a window procedure    }    returnMsg.wparam;}    LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM WPARAM, LPARAM LPARAM) {HDC hdc;    Paintstruct PS;    Rect rect; Switch(message) { CaseWm_create:playsound (TEXT ("Hellowin.wav"), Null,snd_filename | Snd_async);//play a sound file        return 0;  CaseWM_PAINT:HDC= BeginPaint (HWND,&AMP;PS);//mark the start of the window drawingGetClientRect (Hwnd,&rect);//get the size of the window client areaDrawText (HDC, TEXT ("Hello, Windows 98!"), -1, &rect, Dt_singleline | Dt_center | Dt_vcenter);//display a text stringEndPaint (HWND,&AMP;PS);//End Window Drawing        return 0;  CaseWm_destroy:postquitmessage (0);//inserting an "exit" message into a message queue        return 0; }    returnDefWindowProc (Hwnd,message,wparam,lparam);//perform the default message handling}

Prefix	Constant
Cs	Class style options
CW	Create Window Options
Dt	Text drawing Options
IDI	ID number of the icon
Idc	The ID number of the cursor
MB	message box options
Snd	Sound options
Wm	Window messages
Ws	Window style

uint:unsigned int; wparam:unsigned ing; lparam:long.

WINAPI and callback are defined as __stdcall, and the sequence of function calls between windows and applications is established.

Four types of structures:

Structure	Meaning
MSG	Message structure
Wndclass	Window class Structure
Paintstruct	Drawing structures
RECT	Rectangular structure

A handle is essentially a numeric value that refers to an object, and the application uses a handle in other Windows functions to refer to the corresponding object.

Identifier	Meaning
HInstance	Instance handle-The program itself
HWND	Window handle
HDC	Device Environment handle

Hungarian notation: The variable name begins with a lowercase letter indicating the data type of the variable.

Prefix	Data type
C	char or WCHAR or TCHAR
By	BYTE (unsigned character)
N	Short (shorter integer type)
I	int (integral type)
X, y	int, which represents the x-coordinate and y-coordinate
Cx,cy	int, which represents the length of x or Y, and C indicates count (count)
B or F	BOOL (int); F denotes flag
W	WORD (unsigned short integer)
L	Long (integer)
Dw	DWORD (unsigned long integer)
Fn	Function
S	String
Sz	A zero-terminated string
H	Handle
P	Pointer

Chapter III, Windows and messages