c - 为什么 RegisterClassEx 失败

Question

我正在用下面的代码创建一个窗口

int WINAPI WinMain(HINSTANCE hThisInstance, HINSTANCE hPrevInstance, LPSTR lpszArgument, int nCmdShow){
    MSG messages;
    WNDCLASSEX wc;
    DWORD dwrd;

    InitCommonControls();

    //The Window structure
    wc.hInstance = hThisInstance;
    wc.lpszClassName = szClassName;
    wc.lpfnWndProc = WindowProcedure;
    wc.style = CS_DBLCLKS;
    wc.cbSize = sizeof(WNDCLASSEX);

    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION); //if I comment it RegisterClassEx(&wc) fails with error: ERROR_INVALID_PARAMETER
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.lpszMenuName = 0;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;

    wc.hbrBackground = CreateSolidBrush(RGB(230, 225, 208)); //(HBRUSH)(COLOR_3DFACE + 1);

    //Register the window class, and if it fails quit the program
    if(!RegisterClassEx(&wc)){
        dwrd = GetLastError();

        printf("Error in Function = WinMain() at line = %d, with error code = %X \n", __LINE__ - 3, (unsigned int)dwrd);

        exit(EXIT_FAILURE);
    }

    //more code
}

当我注释掉该行时

wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

RegisterClassEx(&wc) 失败并出现错误:ERROR_INVALID_PARAMETER

谢谢

Answer 1

当您注释掉该行时，wc.hIconSm 字段不会被初始化并且可能包含垃圾值。 RegisterClassEx() 恰好注意到这一点并提示。