总结《二》MFC中WinMain和CALLBACK
MFC中WinMain和回调函数CALLBACK
一，路线
1.一般普通窗口或控件建立调用的CWnd :: CreateEx函数
2.经过资源对话框创建的即不调用的CWnd :: CreateEx函数
二，在WIN32SDK下编程我们总是从入口函数WINMAIN和给予窗口类指定窗口回调函数（CALLBACK），如下：
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int WINAPI _tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nShowCmd )
{
WNDCLASSEX wc = { 0 };
wc.cbSize = sizeof(WNDCLASSEX);
wc.hbrBackground = (HBRUSH)GetStockObject(LTGRAY_BRUSH);
wc.hCursor = LoadCursor(nullptr, IDC_ARROW);
wc.hIcon = LoadIcon(nullptr, IDI_APPLICATION);
wc.hInstance = hInstance;
wc.lpfnWndProc = WndProc;//CALLBACK那么MFC隐藏了这些细节，我们具体来解剖下。
三，WINMAIN
在MFC中由appmodul.cpp中声明
extern int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
_In_ LPTSTR lpCmdLine, int nCmdShow);
extern "C" int WINAPI
_tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
_In_ LPTSTR lpCmdLine, int nCmdShow)
#pragma warning(suppress: 4985)
{
// call shared/exported WinMain
return AfxWinMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
}winmain.cpp定义
int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
_In_ LPTSTR lpCmdLine, int nCmdShow)
{
ASSERT(hPrevInstance == NULL);
int nReturnCode = -1;
CWinThread* pThread = AfxGetThread();
CWinApp* pApp = AfxGetApp();
// AFX internal initialization
if (!AfxWinInit(hInstance, hPrevInstance, lpCmdLine, nCmdShow))
goto InitFailure;
// App global initializations (rare)
if (pApp != NULL && !pApp->InitApplication())
goto InitFailure;
// Perform specific initializations
if (!pThread->InitInstance())
{
if (pThread->m_pMainWnd != NULL)
{
TRACE(traceAppMsg, 0, "Warning: Destroying non-NULL m_pMainWnd\n");
pThread->m_pMainWnd->DestroyWindow();
}
nReturnCode = pThread->ExitInstance();
goto InitFailure;
}
nReturnCode = pThread->Run();
InitFailure:
AfxWinTerm();
return nReturnCode;
}三，CALLBACK
分析上述1，先看源码，一切源码说话
BOOL CWnd::CreateEx(DWORD dwExStyle, LPCTSTR lpszClassName,
LPCTSTR lpszWindowName, DWORD dwStyle,
int x, int y, int nWidth, int nHeight,
HWND hWndParent, HMENU nIDorHMenu, LPVOID lpParam)
{
ASSERT(lpszClassName == NULL || AfxIsValidString(lpszClassName) ||
AfxIsValidAtom(lpszClassName));
ENSURE_ARG(lpszWindowName == NULL || AfxIsValidString(lpszWindowName));
// allow modification of several common create parameters
CREATESTRUCT cs;
cs.dwExStyle = dwExStyle;
cs.lpszClass = lpszClassName;
cs.lpszName = lpszWindowName;
cs.style = dwStyle;
cs.x = x;
cs.y = y;
cs.cx = nWidth;
cs.cy = nHeight;
cs.hwndParent = hWndParent;
cs.hMenu = nIDorHMenu;
cs.hInstance = AfxGetInstanceHandle();
cs.lpCreateParams = lpParam;
if (!PreCreateWindow(cs))
{
PostNcDestroy();
return FALSE;
}
AfxHookWindowCreate(this);
HWND hWnd = CreateWindowEx(cs.dwExStyle, cs.lpszClass,
cs.lpszName, cs.style, cs.x, cs.y, cs.cx, cs.cy,
cs.hwndParent, cs.hMenu, cs.hInstance, cs.lpCreateParams);
if (!AfxUnhookWindowCreate())
PostNcDestroy(); // cleanup if CreateWindowEx fails too soon
if (hWnd == NULL)
return FALSE;
ASSERT(hWnd == m_hWnd); // should have been set in send msg hook
return TRUE;
}在正式创建窗口前加入一个的PreCreateWindow的虚函数，这样派生类就有机会重新定义它，当我们想改变窗口类里的属性时可以从派生类覆写此虚函数，也可以我们自己注册窗口类，自己注册后直接返回TRUE即可。
BOOL CWnd::PreCreateWindow(CREATESTRUCT& cs)
{
if (cs.lpszClass == NULL)
{
// make sure the default window class is registered
VERIFY(AfxDeferRegisterClass(AFX_WND_REG));
// no WNDCLASS provided - use child window default
ASSERT(cs.style & WS_CHILD);
cs.lpszClass = _afxWnd;
}
if ((cs.hMenu == NULL) && (cs.style & WS_CHILD))
{
cs.hMenu = (HMENU)(UINT_PTR)this;
}
return TRUE;
}在CreateWindowEx创建窗口之前调用了AfxHookWindowCreate函数，函数源码：
void AFXAPI AfxHookWindowCreate(CWnd* pWnd)
{
_AFX_THREAD_STATE* pThreadState = _afxThreadState.GetData();
if (pThreadState->m_pWndInit == pWnd)
return;
if (pThreadState->m_hHookOldCbtFilter == NULL)
{
pThreadState->m_hHookOldCbtFilter = ::SetWindowsHookEx(WH_CBT,
_AfxCbtFilterHook, NULL, ::GetCurrentThreadId());
if (pThreadState->m_hHookOldCbtFilter == NULL)
AfxThrowMemoryException();
}
ASSERT(pThreadState->m_hHookOldCbtFilter != NULL);
ASSERT(pWnd != NULL);
ASSERT(pWnd->m_hWnd == NULL); // only do once
ASSERT(pThreadState->m_pWndInit == NULL); // hook not already in progress
pThreadState->m_pWndInit = pWnd;
}LRESULT CALLBACK
_AfxCbtFilterHook(int code, WPARAM wParam, LPARAM lParam)
{
_AFX_THREAD_STATE* pThreadState = _afxThreadState.GetData();
if (code != HCBT_CREATEWND)
{
// wait for HCBT_CREATEWND just pass others on...
return CallNextHookEx(pThreadState->m_hHookOldCbtFilter, code,
wParam, lParam);
}
LPCREATESTRUCT lpcs = ((LPCBT_CREATEWND)lParam)->lpcs;
CWnd* pWndInit = pThreadState->m_pWndInit;
BOOL bContextIsDLL = afxContextIsDLL;
if (pWndInit != NULL || (!(lpcs->style & WS_CHILD) && !bContextIsDLL))
{
// Note: special check to avoid subclassing the IME window
if (_afxDBCS)
{
// check for cheap CS_IME style first...
if (GetClassLong((HWND)wParam, GCL_STYLE) & CS_IME)
goto lCallNextHook;
// get class name of the window that is being created
LPCTSTR pszClassName;
TCHAR szClassName[_countof("ime")+1];
if (DWORD_PTR(lpcs->lpszClass) > 0xffff)
{
pszClassName = lpcs->lpszClass;
}
else
{
szClassName[0] = '\0';
#pragma warning(push)
#pragma warning(disable: 4302) // 'type cast' : truncation from 'LPCSTR' to 'ATOM'
GlobalGetAtomName((ATOM)lpcs->lpszClass, szClassName, _countof(szClassName));
#pragma warning(pop)
pszClassName = szClassName;
}
// a little more expensive to test this way, but necessary...
if (::AfxInvariantStrICmp(pszClassName, _T("ime")) == 0)
goto lCallNextHook;
}
ASSERT(wParam != NULL); // should be non-NULL HWND
HWND hWnd = (HWND)wParam;
WNDPROC oldWndProc;
if (pWndInit != NULL)
{
AFX_MANAGE_STATE(pWndInit->m_pModuleState);
// connect the HWND to pWndInit...
pWndInit->Attach(hWnd);
// allow other subclassing to occur first
pWndInit->PreSubclassWindow();
WNDPROC *pOldWndProc = pWndInit->GetSuperWndProcAddr();
ASSERT(pOldWndProc != NULL);
// subclass the window with standard AfxWndProc
WNDPROC afxWndProc = AfxGetAfxWndProc();
oldWndProc = (WNDPROC)SetWindowLongPtr(hWnd, GWLP_WNDPROC,
(DWORD_PTR)afxWndProc);
ASSERT(oldWndProc != NULL);
if (oldWndProc != afxWndProc)
*pOldWndProc = oldWndProc;
pThreadState->m_pWndInit = NULL;
}
else
{
static ATOM s_atomMenu = 0;
bool bSubclass = true;
if (s_atomMenu == 0)
{
WNDCLASSEX wc;
memset(&wc, 0, sizeof(WNDCLASSEX));
wc.cbSize = sizeof(WNDCLASSEX);
s_atomMenu = (ATOM)GetClassInfoEx(NULL, _T("#32768"), &wc);
}
// Do not subclass menus.
if (s_atomMenu != 0)
{
ATOM atomWnd = (ATOM)::GetClassLongPtr(hWnd, GCW_ATOM);
if (atomWnd == s_atomMenu)
bSubclass = false;
}
else
{
TCHAR szClassName[256];
if (::GetClassName(hWnd, szClassName, 256))
{
szClassName[255] = NULL;
if (_tcscmp(szClassName, _T("#32768")) == 0)
bSubclass = false;
}
}
if (bSubclass)
{
// subclass the window with the proc which does gray backgrounds
oldWndProc = (WNDPROC)GetWindowLongPtr(hWnd, GWLP_WNDPROC);
if (oldWndProc != NULL && GetProp(hWnd, _afxOldWndProc) == NULL)
{
SetProp(hWnd, _afxOldWndProc, oldWndProc);
if ((WNDPROC)GetProp(hWnd, _afxOldWndProc) == oldWndProc)
{
GlobalAddAtom(_afxOldWndProc);
SetWindowLongPtr(hWnd, GWLP_WNDPROC, (DWORD_PTR)_AfxActivationWndProc);
ASSERT(oldWndProc != NULL);
}
}
}
}
}
lCallNextHook:
LRESULT lResult = CallNextHookEx(pThreadState->m_hHookOldCbtFilter, code,
wParam, lParam);
return lResult;
}该函数把code不是HCBT_CREATEWND过滤，保留了HCBT_CREATEWND。
该code为一个窗口即将被创建时在向窗口发送WM_CREATE或者WM_NCCREATE消息，所以在这个时候进行了子类化操作，就是把所有的窗口回调函数设为AfxWndProc
LRESULT CALLBACK
AfxWndProc(HWND hWnd, UINT nMsg, WPARAM wParam, LPARAM lParam)
{
// special message which identifies the window as using AfxWndProc
if (nMsg == WM_QUERYAFXWNDPROC)
return 1;
// all other messages route through message map
CWnd* pWnd = CWnd::FromHandlePermanent(hWnd);
ASSERT(pWnd != NULL);
ASSERT(pWnd==NULL || pWnd->m_hWnd == hWnd);
if (pWnd == NULL || pWnd->m_hWnd != hWnd)
return ::DefWindowProc(hWnd, nMsg, wParam, lParam);
return AfxCallWndProc(pWnd, hWnd, nMsg, wParam, lParam);
}
