簡介
函式功能：該函式調用預設的視窗過程來為應用程式沒有處理的任何視窗訊息提供預設的處理。該函式確保每一個訊息得到處理。調用DefWindowProc函式時使用視窗過程接收的相同參數。函式原型：LRESULT DefWindowProc（HWND hWnd，UINT Msg，WPARAM wParam，LPARAM IParam）；
功能
DefWindowProc這個函式是默認的視窗處理函式，我們可以把不關心的訊息都丟給它來處理。這個函式在處理關閉視窗訊息WM_CLOSE時，是調用DestroyWindow函式關閉視窗並且發WM_DESTROY訊息給應用程式；而它對WM_DESTROY這個訊息是不處理的（考慮為什麼？）；我們在應用程式中對這個訊息的處理是發出WM_QUIT訊息。因此WM_CLOSE、WM_DESTROY、WM_QUIT這三個訊息是先後產生的。
參數
hWnd：指向接收訊息的視窗過程的句柄。Msg：指定訊息類型。
wParam：指定其餘的、訊息特定的信息。該參數的內容與Msg參數值有關。
IParam：指定其餘的、訊息特定的信息。該參數的內容與Msg參數值有關。
返回值：返回值就是訊息處理結果，它與傳送的訊息有關。
備註：對於Windows CE；如果Msg為WM_SETTEXT那么返回0。
當DefWindowProc處理WM_DESTROY訊息時，它不自動調用PostQuitMessage。
速查：Windows NT 3.1以上版本；Windows：95以上版本：Windows CE以上版本；頭檔案；winuser.h；庫檔案：user32.lib；Unicode：在Windows NT環境中以Unicode和ANSI版本實現。
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DefWindowProc Function
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The DefWindowProc function calls the default window procedure to provide default processing for any window messages that an application does not process. This function ensures that every message is processed. DefWindowProc is called with the same parameters received by the window procedure.
Syntax
LRESULT DefWindowProc( HWND hWnd,
UINT Msg,
WPARAM wParam,
LPARAM lParam
);
Parameters
hWnd
[in] Handle to the window procedure that received the message.
Msg
[in] Specifies the message.
wParam
[in] Specifies additional message information. The content of this parameter depends on the value of the Msg parameter.
lParam
[in] Specifies additional message information. The content of this parameter depends on the value of the Msg parameter.
Return Value
The return value is the result of the message processing and depends on the message.
Remarks
Windows 95/98/Me: DefWindowProcW is supported by the Microsoft Layer for Unicode (MSLU). To use this, you must add certain files to your application, as outlined in Microsoft Layer for Unicode on Windows 95/98/Me Systems .
Example
For an example, see Designing a Window Procedure.
Function Information
Minimum DLL Version user32.dll
Header Declared in Winuser.h, include Windows.h
Import library User32.lib
Minimum operating systems Windows 95, Windows NT 3.1
Unicode Implemented as ANSI and Unicode versions
範例
/*------------------------------------------------------------HELLOWIN.C -- Displays "Hello, Windows 98!" in client area
(c) Charles Petzold, 1998
------------------------------------------------------------*/
#include
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;//聲明
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow) // 命令行參數，視窗顯示方式
{
static TCHAR szAppName[] = TEXT ("HelloWin") ;
HWND hwnd ;
MSG msg ;
WNDCLASS wndclass ;
wndclass.style = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc = WndProc ;
wndclass.cbClsEx tra = 0 ;
wndclass.cbWndExtra = 0 ;
wndclass.hInstance = hInstance ;
wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;
wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.lpszMenuName = NULL ;
wndclass.lpszClassName = szAppName ;
if (!RegisterClass (&wndclass))
{
MessageBox (NULL, TEXT ("This program requires Windows NT!"),
szAppName, MB_ICONERROR) ;
return 0 ;
}
hwnd = CreateWindow (szAppName, // window class name
TEXT ("The Hello Program"), // window caption
WS_OVERLAPPEDWINDOW, // window style
CW_USEDEFAULT, // initial x position
CW_USEDEFAULT, // initial y position
CW_USEDEFAULT, // initial x size
CW_USEDEFAULT, // initial y size
NULL, // parent window handle
NULL, // window menu handle
hInstance, // program instance handle
NULL) ; // creation parameters
ShowWindow (hwnd, iCmdShow) ;
UpdateWindow (hwnd) ;
while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg) ;//
DispatchMessage (&msg) ;
}
return msg.wParam ;
}
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
HDC hdc ;
PAINTSTRUCT ps ;
RECT rect ;
switch (message)
{
case WM_CREATE:
PlaySound (TEXT ("hellowin.wav"), NULL, SND_FILENAME | SND_ASYNC) ;
return 0 ;
case WM_PAINT:
hdc = BeginPaint (hwnd, &ps) ;
GetClientRect (hwnd, ▭) ;
DrawText (hdc, TEXT ("Hello, Windows 98!"), -1, ▭,
DT_SINGLELINE | DT_CENTER | DT_VCENTER) ;
EndPaint (hwnd, &ps) ;
return 0 ;
case WM_DESTROY:
PostQuitMessage (0) ;
return 0 ;
}
return DefWindowProc (hwnd, message, wParam, lParam) ;
}
