【WM】工作窗口类原理和实现

通过Remote Spy我们常能见到类名为Worker的窗口（如下图所示），那么工作窗口类是什么呢？

其实工作窗口与常规窗口十分相似，只不过我们无需调用RegisterClass()函数注册窗口类，并把我们传入的p参数作为窗口的额外数据保存了起来。想来微软青睐这类不可见的窗口也就是为了简化步骤，提高效率而已。

 

我们先来看看如何创建工作窗口的。在头文件miscsvcs.h内有CreateWorkerWindow()函数的原型声明：

 

//  *************************************************************************
//  CreateWorkerWindow
//
//  Purpose:
//      Helper function to create a worker window
//
//  Parameters:
//      pwszClass   Class name (NULL preferred, unless you need a unique class)
//      pfnWndProc  Window proc for worker window
//      hwndParent  Parent
//      dwExStyle   WS_EX_* styles
//      dwFlags     WS_* styles
//      pwszTitle   Window title
//      hmenu       Menu or child ID
//      p           Comes through in lParam of CREATESTRUCT during WM_CREATE processing
//
//  Returns:
//      HWND of worker window
//
//  Side Effects:
//      none
//  *************************************************************************
HWND CreateWorkerWindow(TCHAR *pwszClass, WNDPROC pfnWndProc, HWND hwndParent,
                        DWORD dwExStyle, DWORD dwFlags, TCHAR *pwszTitle,
                        HMENU hmenu, void * p);

 

下面给出CreateWorkerWindow()函数的实现：

typedef struct tagTEMPPROCPARAMS { LPARAM lParam; WNDPROC pfnWndProc; } TEMPPROCPARAMS, *LPTEMPPROCPARAMS; LRESULT TempWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) { if (uMsg != WM_CREATE) { return DefWindowProc(hwnd, uMsg, wParam, lParam); } else { SetWindowLong(hwnd, 0, ((LPTEMPPROCPARAMS)lParam)->lParam); if (((LPTEMPPROCPARAMS)lParam)->pfnWndProc) { SetWindowLong(hwnd, GWL_WNDPROC, (LONG)((LPTEMPPROCPARAMS)lParam)->pfnWndProc); return ((LPTEMPPROCPARAMS)lParam)->pfnWndProc(hwnd, uMsg, wParam, ((LPTEMPPROCPARAMS)lParam)->lParam); } return NO_ERROR; } } HWND CreateWorkerWindow(TCHAR *pwszClass, WNDPROC pfnWndProc, HWND hwndParent, DWORD dwExStyle, DWORD dwFlags, TCHAR *pwszTitle, HMENU hmenu, void * p) { WNDCLASS wc = {0}; wc.style = CS_DBLCLKS; wc.lpfnWndProc = TempWndProc; wc.cbWndExtra = sizeof(LPARAM); wc.hCursor = LoadCursor(NULL, IDC_ARROW); wc.hbrBackground = (HBRUSH)(COLOR_BTNFACE + 1); wc.lpszClassName = (pwszClass) ? pwszClass : TEXT("Worker"); RegisterClass(&wc); TEMPPROCPARAMS tempProcParams = {(LPARAM)p, pfnWndProc}; return CreateWindowEx(dwExStyle, wc.lpszClassName, pwszTitle, dwFlags, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, hwndParent, hmenu, NULL, &tempProcParams); }