Re: Strange problem about register window class

Thanks very much!


Yes,you are right.


Where is the _stnprintf()?I can't find it in Win32 SDK.


I'm afraid you didn't see clearly.What I wrote is :
reinterpret_cast<HINSTANCE>(&hInstance),it's &hInstance,not
hInstance.So it requires cast.

In Win32 SDK,it says that wc.hInstance is the "Handle to the instance
that the window procedure of this class is within".

But I found even if assigning wc.hInstance with NULL,it's OK.So my
question is:
what use wc.hInstance has?

Below is an example,in which the wndclass.hInstance is assigned with
0.
#include <windows.h>

LRESULT CALLBACK WndProc( HWND, UINT, WPARAM, LPARAM ) ;

int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE,
            PSTR, int iCmdShow )
{
    static TCHAR szAppName[] = "Hello" ;
    HWND hwnd ;
    MSG msg ;
    WNDCLASS wndclass ;

    wndclass.style = CS_HREDRAW | CS_VREDRAW ;
    wndclass.lpfnWndProc = WndProc ;
    wndclass.cbClsExtra = 0 ;
    wndclass.cbWndExtra = 0 ;
    wndclass.hInstance = 0 ;
    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,
             TEXT( "The Hello Program" ),
             WS_OVERLAPPEDWINDOW,
             CW_USEDEFAULT,
             CW_USEDEFAULT,
             CW_USEDEFAULT,
             CW_USEDEFAULT,
             NULL,
             NULL,
             hInstance,
             NULL ) ;

    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_PAINT :
        hdc = BeginPaint( hwnd, &ps ) ;
        GetClientRect( hwnd, &rect ) ;
        DrawText( hdc, "Hello", -1, &rect,
              DT_SINGLELINE | DT_CENTER | DT_VCENTER ) ;
        EndPaint( hwnd, &ps ) ;
        return 0 ;

    case WM_DESTROY :
        PostQuitMessage( 0 ) ;
        return 0 ;
    }
    return DefWindowProc( hwnd, message, wParam, lParam) ;
}