深入解析Windows窗口创建和消息分发

Windows GUI采用基于事件驱动的编程模型，事实上几乎所有的界面库都是这样做的。在纯粹的Window32 SDK编程时代，人们还可以搞懂整个Windows窗体创建和消息的流通过程，但是在现在各种框架的包装下很多在Window32 SDK下很明显易懂的东西显得不是那么简单了。本文力图去繁求简，教你看懂所有框架的基本构造，而事实上对于了解这一切的人来说，这些界面框架的设计都是如出一辙的，希望看完本文，再去看常见的MFC/WTL等框架时，不会再觉得有任何的不适。

C程序的处理办法

1.基本原理

先说古老的Win32 SDK的做法，他们很明显，这里还是先贴上代码，为了缩减篇幅很多地方我就省略了

[cpp] view plaincopy print?

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT ("TestClass");
HWND hwnd;
MSG msg;
WNDCLASSEX wndclassex = {0};
//1.设计窗口类
wndclassex.cbSize = sizeof(WNDCLASSEX);
wndclassex.style = CS_HREDRAW | CS_VREDRAW;
wndclassex.lpfnWndProc = WndProc ...
//2.注册窗口类
if (!RegisterClassEx (&wndclassex))
{
MessageBox (NULL, TEXT ("RegisterClassEx failed!"), szAppName, MB_ICONERROR);
return 0;
}
//3.创建窗口
hwnd = CreateWindowEx (WS_EX_OVERLAPPEDWINDOW,
szAppName,
...
//4.显示窗口
ShowWindow (hwnd, iCmdShow);
UpdateWindow (hwnd);
//5.开始消息循环，又称消息泵
while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg);
DispatchMessage (&msg);
}
return msg.wParam;
}
//回调函数中做消息分发
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
HDC hdc;
PAINTSTRUCT ps;
//分发
switch (message)
{
case WM_CREATE:
return (0);
case WM_PAINT:
...
return (0);
case WM_DESTROY:
PostQuitMessage (0);
return (0);
}
//默认处理函数
return DefWindowProc (hwnd, message, wParam, lParam);
}

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{static TCHAR szAppName[] = TEXT ("TestClass");HWND         hwnd;MSG          msg;WNDCLASSEX   wndclassex = {0};//1.设计窗口类wndclassex.cbSize        = sizeof(WNDCLASSEX);wndclassex.style         = CS_HREDRAW | CS_VREDRAW;wndclassex.lpfnWndProc   = WndProc ...//2.注册窗口类if (!RegisterClassEx (&wndclassex)){MessageBox (NULL, TEXT ("RegisterClassEx failed!"), szAppName, MB_ICONERROR);return 0;}//3.创建窗口hwnd = CreateWindowEx (WS_EX_OVERLAPPEDWINDOW, szAppName, ...//4.显示窗口ShowWindow (hwnd, iCmdShow);UpdateWindow (hwnd);//5.开始消息循环，又称消息泵while (GetMessage (&msg, NULL, 0, 0)){TranslateMessage (&msg);DispatchMessage (&msg);}return msg.wParam;
}//回调函数中做消息分发
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{HDC hdc;PAINTSTRUCT ps;//分发switch (message){case WM_CREATE:return (0);case WM_PAINT:...return (0);case WM_DESTROY:PostQuitMessage (0);return (0);}//默认处理函数return DefWindowProc (hwnd, message, wParam, lParam);
}

设计窗口类和注册窗口类可称为 InitApplication，即初始化Windows 应用所需要做的工作，这个窗口类 可以是公用的。

创建一个窗口和显示可称为InitInstance，即初始化一个Windows 应用实例所需要做的工作，对每个窗体来说这都是唯一的，可做定制化修改。

开启消息泵可称为Run，一单消息泵开启，意味着一个程序开始接受消息和分发消息，整个应用程序算是开始运行了。

在WndProc中做的是判断对应的消息，然后做对应的处理工作。

2.改进窗口创建

可以看到，最原始的Win32 SDK编程完全是面向过程编程创建，比较繁琐，为了简化编写，可在VS2008里面打开新建一个Win32 程序可以看到代码如下:

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// 1.设计和注册消息类
...
MyRegisterClass(hInstance);
// 2.执行应用程序初始化:
if (!InitInstance (hInstance, nCmdShow))
{
return FALSE;
}
hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_WIN321));
// 3.主消息循环:
while (GetMessage(&msg, NULL, 0, 0))
{
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
return (int) msg.wParam;

 // 1.设计和注册消息类...MyRegisterClass(hInstance);// 2.执行应用程序初始化:if (!InitInstance (hInstance, nCmdShow)){return FALSE;}hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_WIN321));// 3.主消息循环:while (GetMessage(&msg, NULL, 0, 0)){if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg)){TranslateMessage(&msg);DispatchMessage(&msg);}}return (int) msg.wParam;

可以看到按照在基本原理中讲的，这里微软的做法也一样， 按照三大部分封装到函数中，简化操作，InitApplication命名成了MyRegisterClass而已。

3.改进消息分发

前面讲了改进窗口创建，但是消息分发仍然是一团乱麻，所有的消息响应都塞在switch case中，这里我们自然想到和窗口创建一样，对应的处理分发到函数中。而事实上微软也确实是这么做的，微软提供了头文件WindowsX.h来帮助我们分发消息，具体如下:

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LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
HANDLE_MSG(hWnd, WM_PAINT, Cls_OnPaint);
HANDLE_MSG(hWnd, WM_DESTROY, Cls_OnDestroy);
}
return DefWindowProc(hWnd, message, wParam, lParam);
}
void Cls_OnPaint(HWND hwnd)
{
HDC hdc;
PAINTSTRUCT ps;
hdc = BeginPaint(hwnd, &ps);
//...
EndPaint(hwnd, &ps);
}
void Cls_OnDestroy(HWND hwnd)
{
PostQuitMessage(0);
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{switch (message){HANDLE_MSG(hWnd, WM_PAINT, Cls_OnPaint);HANDLE_MSG(hWnd, WM_DESTROY, Cls_OnDestroy);}return DefWindowProc(hWnd, message, wParam, lParam);
}void Cls_OnPaint(HWND hwnd)
{HDC hdc;PAINTSTRUCT ps;hdc = BeginPaint(hwnd, &ps);//...EndPaint(hwnd, &ps);
}void Cls_OnDestroy(HWND hwnd)
{PostQuitMessage(0);
}

可以看到，这里借助于HANDLE_MSG宏让消息对应到具体的处理函数上，HANDLE_MSG展开如下：

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#define HANDLE_MSG(hwnd, message, fn) \
case (message): return HANDLE_##message((hwnd), (wParam), (lParam), (fn))

#define HANDLE_MSG(hwnd, message, fn)    \case (message): return HANDLE_##message((hwnd), (wParam), (lParam), (fn))

HANDLE##message为处理函数
可看到这里 借助宏来减少switch case代码的编写量，但实际代码内容是一样的。

实际上对话框的处理略有不同，如下:

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#define chHANDLE_DLGMSG(hwnd, message, fn) case (message): \
return (SetDlgMsgResult(hwnd, uMsg, HANDLE_##message((hwnd), (wParam), (lParam), (fn))))
INT_PTR CALLBACK Dlg_Proc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
UNREFERENCED_PARAMETER(lParam);
switch (message)
{
chHANDLE_DLGMSG(hwnd, WM_INITDIALOG, Dlg_OnInitDialog);
chHANDLE_DLGMSG(hwnd, WM_COMMAND, Dlg_OnCommand);
}
return (INT_PTR)FALSE;
}

#define chHANDLE_DLGMSG(hwnd, message, fn) case (message): \return (SetDlgMsgResult(hwnd, uMsg, HANDLE_##message((hwnd), (wParam), (lParam), (fn))))INT_PTR CALLBACK Dlg_Proc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{UNREFERENCED_PARAMETER(lParam);switch (message){chHANDLE_DLGMSG(hwnd, WM_INITDIALOG, Dlg_OnInitDialog);chHANDLE_DLGMSG(hwnd, WM_COMMAND,    Dlg_OnCommand);}return (INT_PTR)FALSE;
}

这里的chHANDLE_DLGMSG是仿照HANDLE_MSG自定义的。

C++程序的处理办法

在C++时代，人们提倡面向对象编程，对于窗口的创建和消息的分发响应都是窗口的行为，所以几乎所有的框架都是想办法把这两者封装在一起，这也是我们讲解的重点。对于C++程序我们先讲大框架，再讲窗口类封装。

1.MFC大框架

盗用侯捷先生一张图，MFC的基本层次结构如下:

MFC将开启消息循环放到CWinThread中，将窗口注册、创建、消息分发响应均放到CWnd中处理，这样所有和窗口处理相关的都是由同一个类来完成，符合C++的封装特性，也便于使用。

VS安装完目录VC\atlmfc\src\mfc下有部分mfc源码，我们直接看微软的实现。

首先，入口文件appmodul.cpp中定义入口如下:

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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);
}

extern "C" int WINAPI _tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, _In_ LPTSTR lpCmdLine, int nCmdShow)
#pragma warning(suppress: 4985)
{// call shared/exported WinMainreturn AfxWinMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
}

然后，在winmain.cpp查看定义AfxWinMain如下

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int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, _In_ LPTSTR lpCmdLine, int nCmdShow)
{
...
// 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())
{
...
}
nReturnCode = pThread->Run();
...
}

int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, _In_ LPTSTR lpCmdLine, int nCmdShow)
{...// AFX internal initializationif (!AfxWinInit(hInstance, hPrevInstance, lpCmdLine, nCmdShow))goto InitFailure;// App global initializations (rare)if (pApp != NULL && !pApp->InitApplication())goto InitFailure;// Perform specific initializationsif (!pThread->InitInstance()){...}nReturnCode = pThread->Run();...
}

所以还是InitApplication、InitInstance、Run三大块，AfxWinInit用于做一些框架的初始化工作。

CWinApp::InitApplication在appcore.cpp中，和C程序略有不同，这里的工作主要是Doc模板管理器的初始化工作。

CThread::InitInstance虚函数会被用户改写，在这当中调用CWnd完成窗口的注册和创建，这个在之后一起讲

CThread::Run在thrdcore.cpp中，Run-》PumpMessage-》AfxInternalPumpMessage完成消息泵的开启，如下:

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BOOL AFXAPI AfxInternalPumpMessage()
{
_AFX_THREAD_STATE *pState = AfxGetThreadState();
if (!::GetMessage(&(pState->m_msgCur), NULL, NULL, NULL))
{
...
return FALSE;
}
...
if (pState->m_msgCur.message != WM_KICKIDLE && !AfxPreTranslateMessage(&(pState->m_msgCur)))
{
::TranslateMessage(&(pState->m_msgCur));
::DispatchMessage(&(pState->m_msgCur));
}
return TRUE;
}

BOOL AFXAPI AfxInternalPumpMessage()
{_AFX_THREAD_STATE *pState = AfxGetThreadState();if (!::GetMessage(&(pState->m_msgCur), NULL, NULL, NULL)){
...return FALSE;}...if (pState->m_msgCur.message != WM_KICKIDLE && !AfxPreTranslateMessage(&(pState->m_msgCur))){::TranslateMessage(&(pState->m_msgCur));::DispatchMessage(&(pState->m_msgCur));}return TRUE;
}

2.MFC封装窗口创建和消息分发

利用C++面向对象的特征，将窗口创建和消息分发、响应分装在一个类中，这样一个窗口类对应一个实际窗口，非常简单直观。

首先我们思考下，把窗口创建和消息分发封装在一起有哪些难点？

1.怎么将不同的窗口过程勾到一起

历史经验告诉我们，专制往往有时候好办事。如果每个窗口都有自己的窗口过程，那样处理起来就比较麻烦，最好的做法是所有的窗口在同一个窗口过程中控制分发。

2.同一窗口过程中怎样将不同的hwnd消息分发给对应的CWnd类去处理响应

因为窗口回调函数的限制，回调函数不能拥有对应CWnd类的this指针，也就是说来了窗口消息，怎样才能辨别对应的hwnd对应的CWnd，把消息分发给CWnd去处理呢？

3.最后，如果CWnd拿到了消息，怎样去简单有效的去处理和响应呢

我们说过消息的响应也是在Cwnd中处理，怎样将拿到的消息对应成具体的类成员函数呢？

这些问题串通后，MFC的做法，我们画一张消息流通图如下：

a).窗口创建

同样我们拿源码来解释，

在MFC中我们自定义的窗口类继承关系如下:

CWnd->CFrameWnd->CMyFrameWnd

winfrm.cpp中CFrameWnd::LoadFrame

首先，调用GetIconWndClass->AfxRegisterWndClass完成窗口类设计和注册，

然后，调用CFrameWnd::Create->CWnd::CreateEx完成窗口创建，如下:

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BOOL CFrameWnd::LoadFrame(UINT nIDResource, DWORD dwDefaultStyle, CWnd* pParentWnd, CCreateContext* pContext)
{
...
LPCTSTR lpszClass = GetIconWndClass(dwDefaultStyle, nIDResource);
CString strTitle = m_strTitle;
if (!Create(lpszClass, strTitle, dwDefaultStyle, rectDefault, pParentWnd, ATL_MAKEINTRESOURCE(nIDResource), 0L, pContext))
{
return FALSE; // will self destruct on failure normally
}
...
}

BOOL CFrameWnd::LoadFrame(UINT nIDResource, DWORD dwDefaultStyle, CWnd* pParentWnd, CCreateContext* pContext)
{
...LPCTSTR lpszClass = GetIconWndClass(dwDefaultStyle, nIDResource);CString strTitle = m_strTitle;if (!Create(lpszClass, strTitle, dwDefaultStyle, rectDefault, pParentWnd, ATL_MAKEINTRESOURCE(nIDResource), 0L, pContext)){return FALSE;   // will self destruct on failure normally}...
}

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LPCTSTR CFrameWnd::GetIconWndClass(DWORD dwDefaultStyle, UINT nIDResource)
{
...
if (hIcon != NULL)
{
...
{
// register a very similar WNDCLASS
return AfxRegisterWndClass(wndcls.style, wndcls.hCursor, wndcls.hbrBackground, hIcon);
}
}
return NULL; // just use the default
}

LPCTSTR CFrameWnd::GetIconWndClass(DWORD dwDefaultStyle, UINT nIDResource)
{
...if (hIcon != NULL){
...{// register a very similar WNDCLASSreturn AfxRegisterWndClass(wndcls.style, wndcls.hCursor, wndcls.hbrBackground, hIcon);}}return NULL;        // just use the default
}

在wincore.cpp的CWnd::CreateEx中， 创建窗口

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BOOL CWnd::CreateEx(...)
{
...
// 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;
...
AfxHookWindowCreate(this);
HWND hWnd = ::AfxCtxCreateWindowEx(cs.dwExStyle, cs.lpszClass,
cs.lpszName, cs.style, cs.x, cs.y, cs.cx, cs.cy,
cs.hwndParent, cs.hMenu, cs.hInstance, cs.lpCreateParams);
...
}

BOOL CWnd::CreateEx(...)
{
...// allow modification of several common create parametersCREATESTRUCT 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;...AfxHookWindowCreate(this);HWND hWnd = ::AfxCtxCreateWindowEx(cs.dwExStyle, cs.lpszClass,cs.lpszName, cs.style, cs.x, cs.y, cs.cx, cs.cy,cs.hwndParent, cs.hMenu, cs.hInstance, cs.lpCreateParams);...
}

其中，在 AfxHookWindowCreate中 安装钩子使所有窗口消息勾到一起处理如下:

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void AFXAPI AfxHookWindowCreate(CWnd* pWnd)
{
...
pThreadState->m_hHookOldCbtFilter = ::SetWindowsHookEx(WH_CBT, _AfxCbtFilterHook, NULL, ::GetCurrentThreadId());
...
}

void AFXAPI AfxHookWindowCreate(CWnd* pWnd)
{
...pThreadState->m_hHookOldCbtFilter = ::SetWindowsHookEx(WH_CBT, _AfxCbtFilterHook, NULL, ::GetCurrentThreadId());...
}

在_AfxCbtFilterHook中代码如下：

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LRESULT CALLBACK _AfxCbtFilterHook(int code, WPARAM wParam, LPARAM lParam)
{
...
if (pWndInit != NULL)
{
AFX_MANAGE_STATE(pWndInit->m_pModuleState);
// the window should not be in the permanent map at this time
ASSERT(CWnd::FromHandlePermanent(hWnd) == NULL);
// 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;
...
}

LRESULT CALLBACK _AfxCbtFilterHook(int code, WPARAM wParam, LPARAM lParam)
{
...if (pWndInit != NULL){AFX_MANAGE_STATE(pWndInit->m_pModuleState);// the window should not be in the permanent map at this timeASSERT(CWnd::FromHandlePermanent(hWnd) == NULL);// connect the HWND to pWndInit...pWndInit->Attach(hWnd);// allow other subclassing to occur firstpWndInit->PreSubclassWindow();WNDPROC *pOldWndProc = pWndInit->GetSuperWndProcAddr();ASSERT(pOldWndProc != NULL);// subclass the window with standard AfxWndProcWNDPROC afxWndProc = AfxGetAfxWndProc();oldWndProc = (WNDPROC)SetWindowLongPtr(hWnd, GWLP_WNDPROC,(DWORD_PTR)afxWndProc);ASSERT(oldWndProc != NULL);if (oldWndProc != afxWndProc)*pOldWndProc = oldWndProc;...
}

其中pWndInit->Attach完成 句柄hwnd和窗口类CWnd*的绑定，建立一张hash表，对应的HashMap结构可参照CWnd::afxMapHWND对应的winhand_.h中的CHandleMap

SetWindowLongPtr使所有的窗口响应都走AfxWndProc中,在AfxWndProc中完成消息分发到对应的Cwnd中。

b).消息的分发和响应

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LRESULT CALLBACK AfxWndProc(HWND hWnd, UINT nMsg, WPARAM wParam, LPARAM lParam)
{
...
// all other messages route through message map
CWnd* pWnd = CWnd::FromHandlePermanent(hWnd);
...
return AfxCallWndProc(pWnd, hWnd, nMsg, wParam, lParam);
}

LRESULT CALLBACK AfxWndProc(HWND hWnd, UINT nMsg, WPARAM wParam, LPARAM lParam)
{
...// all other messages route through message mapCWnd* pWnd = CWnd::FromHandlePermanent(hWnd);...return AfxCallWndProc(pWnd, hWnd, nMsg, wParam, lParam);
}

可以看到，根据hwnd取得对应的CWnd*，然后看AfxCallWndProc如下:

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LRESULT AFXAPI AfxCallWndProc(CWnd* pWnd, HWND hWnd, UINT nMsg, WPARAM wParam = 0, LPARAM lParam = 0)
{
...
// delegate to object's WindowProc
lResult = pWnd->WindowProc(nMsg, wParam, lParam);
...
}

LRESULT AFXAPI AfxCallWndProc(CWnd* pWnd, HWND hWnd, UINT nMsg, WPARAM wParam = 0, LPARAM lParam = 0)
{
...// delegate to object's WindowProclResult = pWnd->WindowProc(nMsg, wParam, lParam);
...
}

在这里开始 调用CWnd成员响应函数，终于又回到CWnd中了，接着往下看

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LRESULT CWnd::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
{
...
if (!OnWndMsg(message, wParam, lParam, &lResult))
...
}

LRESULT CWnd::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
{
...if (!OnWndMsg(message, wParam, lParam, &lResult))...
}

在OnWndMsg中做了什么呢？看下面代码

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BOOL CWnd::OnWndMsg(UINT message, WPARAM wParam, LPARAM lParam, LRESULT* pResult)
{
...
//WM_COMMAND特殊处理
if (message == WM_COMMAND)
{
if (OnCommand(wParam, lParam))
{
lResult = 1;
goto LReturnTrue;
}
return FALSE;
}
...
//找到当前的CWnd类的MessageMap表，查表得到对应响应函数并处理
const AFX_MSGMAP* pMessageMap; pMessageMap = GetMessageMap();
...
for (/* pMessageMap already init'ed */; pMessageMap->pfnGetBaseMap != NULL;
pMessageMap = (*pMessageMap->pfnGetBaseMap)())
{
...
}
...
}

BOOL CWnd::OnWndMsg(UINT message, WPARAM wParam, LPARAM lParam, LRESULT* pResult)
{
...//WM_COMMAND特殊处理if (message == WM_COMMAND){if (OnCommand(wParam, lParam)){lResult = 1;goto LReturnTrue;}return FALSE;}
...//找到当前的CWnd类的MessageMap表，查表得到对应响应函数并处理const AFX_MSGMAP* pMessageMap; pMessageMap = GetMessageMap();...for (/* pMessageMap already init'ed */; pMessageMap->pfnGetBaseMap != NULL;pMessageMap = (*pMessageMap->pfnGetBaseMap)()){...}...
}

可以看到，到此 完成了CWnd中的查表调用消息对应的处理函数，至于具体的OnCommand消息处理和具体响应函数调用过程，恕不详述。

但是等等，还有一个问题没有解决，那就是CWnd中的消息-处理函数表怎么来的，这就是我们常见的如下结构

[cpp] view plaincopy print?

BEGIN_MESSAGE_MAP(CMainFrame, ...)
ON_WM_CREATE()
ON_WM_SETFOCUS()
...
END_MESSAGE_MAP()

BEGIN_MESSAGE_MAP(CMainFrame, ...)ON_WM_CREATE()ON_WM_SETFOCUS()
...
END_MESSAGE_MAP()

头文件中的DECLARE_MESSAGE_MAP定义如下，可以看到回调函数中 取消息映射表的函数GetMessageMap在此定义

[cpp] view plaincopy print?

#define DECLARE_MESSAGE_MAP() \
protected: \
static const AFX_MSGMAP* PASCAL GetThisMessageMap(); \
virtual const AFX_MSGMAP* GetMessageMap() const; \

#define DECLARE_MESSAGE_MAP() \
protected: \static const AFX_MSGMAP* PASCAL GetThisMessageMap(); \virtual const AFX_MSGMAP* GetMessageMap() const; \

BEGIN_MESSAGE_MAP结构展开如下

[cpp] view plaincopy print?

#define BEGIN_MESSAGE_MAP(theClass, baseClass) \
PTM_WARNING_DISABLE \
const AFX_MSGMAP* theClass::GetMessageMap() const \
{ return GetThisMessageMap(); } \
const AFX_MSGMAP* PASCAL theClass::GetThisMessageMap() \
{ \
typedef theClass ThisClass; \
typedef baseClass TheBaseClass; \
static const AFX_MSGMAP_ENTRY _messageEntries[] = \
{

#define BEGIN_MESSAGE_MAP(theClass, baseClass) \PTM_WARNING_DISABLE \const AFX_MSGMAP* theClass::GetMessageMap() const \{ return GetThisMessageMap(); } \const AFX_MSGMAP* PASCAL theClass::GetThisMessageMap() \{ \typedef theClass ThisClass;                         \typedef baseClass TheBaseClass;                    \static const AFX_MSGMAP_ENTRY _messageEntries[] =  \{

可见 真正的映射表结构_massgeEntries在此定义,ON_WM_CRATE完成实际的表内容填充，例如:

[cpp] view plaincopy print?

#define ON_WM_CREATE() \
{ WM_CREATE, 0, 0, 0, AfxSig_is, \
(AFX_PMSG) (AFX_PMSGW) \
(static_cast< int (AFX_MSG_CALL CWnd::*)(LPCREATESTRUCT) > ( &ThisClass :: OnCreate)) },

#define ON_WM_CREATE() \{ WM_CREATE, 0, 0, 0, AfxSig_is, \(AFX_PMSG) (AFX_PMSGW) \(static_cast< int (AFX_MSG_CALL CWnd::*)(LPCREATESTRUCT) > ( &ThisClass :: OnCreate)) },

将 WM_CREATE和OnCreate函数绑定

至此，窗口类的封装过程尽在眼前，可能你觉得过程比较繁琐，那么我把它概括如下:

1.Create窗口时完成两件事:(1)窗口过程勾到一起处理(2)hwnd和对应的CWnd*绑定

2.CWnd中利用BEGIN_MESSAGE_MAP结构定义【消息-响应函数】的路由表

3.响应函数中根据传入的hwnd查表得到CWnd*，调用CWnd->GetMassageMap获取【消息-响应函数】表，查对应消息的响应函数，调用完成响应

现在再返回去看，是不是清晰明朗了？

3.ATL大框架

MFC出现在C++尚未完善时，没有采用c++的高级特性，基本上都是继承和虚函数、查表，类的层次过多，显得比较臃肿。相比而言，ATL就好多了，采用模板技术简化了设计，也没有那么多的层次结构，非常轻量，在此基础上上封装的WTL界面库被越来越多的人使用。WTL虽然是在ATL上封装的，但是窗口的创建和消息分发原理并没有变，所以我们仍然以ATL来讲解整个过程。

ATL的框架基本上是自己搭建起来的，自己编写_tWinMain函数，期间可借助CMessageLoop完成消息泵的开启，如下：

[cpp] view plaincopy print?

int WINAPI _tWinMain(HINSTANCE hInstance, HINSTANCE /*hPrevInstance*/, LPTSTR lpstrCmdLine, int nCmdShow)
{
...
int nRet = Run(lpstrCmdLine, nCmdShow);
...
}
int Run(LPTSTR /*lpstrCmdLine*/ = NULL, int nCmdShow = SW_SHOWDEFAULT)
{
CMessageLoop theLoop;
_Module.AddMessageLoop(&theLoop);
CMainFrame wndMain;
if(wndMain.CreateEx() == NULL)
{
ATLTRACE(_T("Main window creation failed!\n"));
return 0;
}
wndMain.ShowWindow(nCmdShow);
int nRet = theLoop.Run();
_Module.RemoveMessageLoop();
return nRet;
}

int WINAPI _tWinMain(HINSTANCE hInstance, HINSTANCE /*hPrevInstance*/, LPTSTR lpstrCmdLine, int nCmdShow)
{
...int nRet = Run(lpstrCmdLine, nCmdShow);
...
}int Run(LPTSTR /*lpstrCmdLine*/ = NULL, int nCmdShow = SW_SHOWDEFAULT)
{CMessageLoop theLoop;_Module.AddMessageLoop(&theLoop);CMainFrame wndMain;if(wndMain.CreateEx() == NULL){ATLTRACE(_T("Main window creation failed!\n"));return 0;}wndMain.ShowWindow(nCmdShow);int nRet = theLoop.Run();_Module.RemoveMessageLoop();return nRet;
}

可知CMainFrame::CreateEx完成窗口创建，atlapp.h中CMessageLoop完成消息泵开启，代码如下:

[cpp] view plaincopy print?

// message loop
int Run()
{
...
for(;;)
{
...
bRet = ::GetMessage(&m_msg, NULL, 0, 0);
...
if(!PreTranslateMessage(&m_msg))
{
::TranslateMessage(&m_msg);
::DispatchMessage(&m_msg);
}
...
}
return (int)m_msg.wParam;
}

// message loopint Run(){
...for(;;){
...bRet = ::GetMessage(&m_msg, NULL, 0, 0);
...if(!PreTranslateMessage(&m_msg)){::TranslateMessage(&m_msg);::DispatchMessage(&m_msg);}
...}return (int)m_msg.wParam;}

整个大框架和Win32 SDK很像，没什么封装，唯一不同的是所有的窗口创建和消息分发都封装到窗口类中了，这个接下来重点说说。

4.ATL封装窗口创建和消息分发

和MFC封装窗口类一样，这里同样需要考虑之前说的三个问题，重要的事情说三遍，我就再贴一次之前的话。

1.怎么将不同的窗口过程勾到一起

2.同一窗口过程中怎样将不同的hwnd消息分发给对应的CWnd类去处理响应

3.最后，如果CWnd拿到了消息，怎样去简单有效的去处理和响应呢

这里和MFC一样，

1.所有的窗体窗口过程函数一样，保证统一处理

2.hwnd和对应窗口类是通过汇编强制粘连起来的

3.CWnd拿到消息后类似前面的C语言通过一组宏简化switch case结构调用对应的消息响应函数

同样我们从源码开始入手:

所有的窗体类都继承于CWndImpl，我们关注这个类即可

a).窗口创建

atlwin.app中CWindowImpl::Create中如下，取得窗口信息，注册窗口类

[cpp] view plaincopy print?

HWND Create(HWND hWndParent, _U_RECT rect = NULL, LPCTSTR szWindowName = NULL,
DWORD dwStyle = 0, DWORD dwExStyle = 0,
_U_MENUorID MenuOrID = 0U, LPVOID lpCreateParam = NULL)
{
if (T::GetWndClassInfo().m_lpszOrigName == NULL)
T::GetWndClassInfo().m_lpszOrigName = GetWndClassName();
ATOM atom = T::GetWndClassInfo().Register(&m_pfnSuperWindowProc);
dwStyle = T::GetWndStyle(dwStyle);
dwExStyle = T::GetWndExStyle(dwExStyle);
...
return CWindowImplBaseT< TBase, TWinTraits >::Create(hWndParent, rect, szWindowName,
dwStyle, dwExStyle, MenuOrID, atom, lpCreateParam);
}

HWND Create(HWND hWndParent, _U_RECT rect = NULL, LPCTSTR szWindowName = NULL,DWORD dwStyle = 0, DWORD dwExStyle = 0,_U_MENUorID MenuOrID = 0U, LPVOID lpCreateParam = NULL)
{if (T::GetWndClassInfo().m_lpszOrigName == NULL)T::GetWndClassInfo().m_lpszOrigName = GetWndClassName();ATOM atom = T::GetWndClassInfo().Register(&m_pfnSuperWindowProc);dwStyle = T::GetWndStyle(dwStyle);dwExStyle = T::GetWndExStyle(dwExStyle);...return CWindowImplBaseT< TBase, TWinTraits >::Create(hWndParent, rect, szWindowName,dwStyle, dwExStyle, MenuOrID, atom, lpCreateParam);
}

可以看到调用 GetWndClassInfo.Register注册窗口类，每个类中使用DECLARE_WND_CLASS等宏来填充对应信息。

DECLARE_WND_CLASS展开如下:

[cpp] view plaincopy print?

#define DECLARE_WND_CLASS(WndClassName) \
static ATL::CWndClassInfo& GetWndClassInfo() \
{ \
static ATL::CWndClassInfo wc = \
{ \
{ sizeof(WNDCLASSEX), CS_HREDRAW | CS_VREDRAW | CS_DBLCLKS, StartWindowProc, \
0, 0, NULL, NULL, NULL, (HBRUSH)(COLOR_WINDOW + 1), NULL, WndClassName, NULL }, \
NULL, NULL, IDC_ARROW, TRUE, 0, _T("") \
}; \
return wc; \
}

#define DECLARE_WND_CLASS(WndClassName) \
static ATL::CWndClassInfo& GetWndClassInfo() \
{ \static ATL::CWndClassInfo wc = \{ \{ sizeof(WNDCLASSEX), CS_HREDRAW | CS_VREDRAW | CS_DBLCLKS, StartWindowProc, \0, 0, NULL, NULL, NULL, (HBRUSH)(COLOR_WINDOW + 1), NULL, WndClassName, NULL }, \NULL, NULL, IDC_ARROW, TRUE, 0, _T("") \}; \return wc; \
}

可知默认的 所有窗口的窗口过程函数是StartWindowProc，完成统一控制
实际的 窗口创建函数如下：

[cpp] view plaincopy print?

template <class TBase, class TWinTraits>
HWND CWindowImplBaseT< TBase, TWinTraits >::Create(...)
{
BOOL result;
ATLASSUME(m_hWnd == NULL);
// 初始化Thunk结构体
result = m_thunk.Init(NULL,NULL);
...
//保存当前窗口类指针到全局
_AtlWinModule.AddCreateWndData(&m_thunk.cd, this);
//创建窗口
HWND hWnd = ::CreateWindowEx(dwExStyle, MAKEINTATOM(atom), szWindowName,
dwStyle, rect.m_lpRect->left, rect.m_lpRect->top, rect.m_lpRect->right - rect.m_lpRect->left,
rect.m_lpRect->bottom - rect.m_lpRect->top, hWndParent, MenuOrID.m_hMenu,
_AtlBaseModule.GetModuleInstance(), lpCreateParam);
...
}

template <class TBase, class TWinTraits>
HWND CWindowImplBaseT< TBase, TWinTraits >::Create(...)
{BOOL result;ATLASSUME(m_hWnd == NULL);// 初始化Thunk结构体result = m_thunk.Init(NULL,NULL);
...//保存当前窗口类指针到全局_AtlWinModule.AddCreateWndData(&m_thunk.cd, this);//创建窗口HWND hWnd = ::CreateWindowEx(dwExStyle, MAKEINTATOM(atom), szWindowName,dwStyle, rect.m_lpRect->left, rect.m_lpRect->top, rect.m_lpRect->right - rect.m_lpRect->left,rect.m_lpRect->bottom - rect.m_lpRect->top, hWndParent, MenuOrID.m_hMenu,_AtlBaseModule.GetModuleInstance(), lpCreateParam);
...
}

这里的Thunk和保存指针到全局之后再说。

至此创建过程完成。

b).消息分发和响应

前面说了，所有的窗口类的响应函数都是在StartWndProc中，如下:

[cpp] view plaincopy print?

template <class TBase, class TWinTraits>
LRESULT CALLBACK CWindowImplBaseT< TBase, TWinTraits >::StartWindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
CWindowImplBaseT< TBase, TWinTraits >* pThis = (CWindowImplBaseT< TBase, TWinTraits >*)_AtlWinModule.ExtractCreateWndData();
...
pThis->m_thunk.Init(pThis->GetWindowProc(), pThis);
WNDPROC pProc = pThis->m_thunk.GetWNDPROC();
WNDPROC pOldProc = (WNDPROC)::SetWindowLongPtr(hWnd, GWLP_WNDPROC, (LONG_PTR)pProc);
...
return pProc(hWnd, uMsg, wParam, lParam);
}

template <class TBase, class TWinTraits>
LRESULT CALLBACK CWindowImplBaseT< TBase, TWinTraits >::StartWindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{CWindowImplBaseT< TBase, TWinTraits >* pThis = (CWindowImplBaseT< TBase, TWinTraits >*)_AtlWinModule.ExtractCreateWndData();...pThis->m_thunk.Init(pThis->GetWindowProc(), pThis);WNDPROC pProc = pThis->m_thunk.GetWNDPROC();WNDPROC pOldProc = (WNDPROC)::SetWindowLongPtr(hWnd, GWLP_WNDPROC, (LONG_PTR)pProc);...return pProc(hWnd, uMsg, wParam, lParam);
}

可知， 第一次窗口响应会进入到此函数，这里的代码从全局结构中拿到当前窗口类的指针，初始化Thunk，设置Thunk为代理窗口响应函数，通过pThis->m_thunk.Init(pThis->GetWindowProc(), pThis); 将窗口的this指针和窗口消息处理函数WindowProc初始化到thunk静态结构里。设置所有的窗体过程函数为WindowProc。

这里用到了Thunk转换技术，所谓Thunk就是转换的意思，这里的基本思想是替换掉传统的WndProc的第一个句柄参数hwnd,让这里的hwnd实际上是对应的CWndImpl的指针，这样完成了hwnd到窗体类的映射。具体的实现在atlstdthunk.h中，如下:

[cpp] view plaincopy print?

#pragma pack(push,1)
struct _stdcallthunk
{
DWORD m_mov; // 替换hwnd参数为对应CWndImpl指针 mov dword ptr [esp+0x4], pThis (esp+0x4 is hWnd)
DWORD m_this; //
BYTE m_jmp; // 跳转到WndProc
DWORD m_relproc; // relative jmp
BOOL Init(DWORD_PTR proc, void* pThis)
{
m_mov = 0x042444C7; //C7 44 24 0C
m_this = PtrToUlong(pThis);
m_jmp = 0xe9;
m_relproc = DWORD((INT_PTR)proc - ((INT_PTR)this+sizeof(_stdcallthunk))); // write block from data cache and
FlushInstructionCache(GetCurrentProcess(), this, sizeof(_stdcallthunk)); // flush from instruction cache
return TRUE;
}
...
};
#pragma pack(pop)

#pragma pack(push,1)
struct _stdcallthunk
{DWORD   m_mov;          // 替换hwnd参数为对应CWndImpl指针 mov dword ptr [esp+0x4], pThis (esp+0x4 is hWnd)DWORD   m_this;         //BYTE    m_jmp;          // 跳转到WndProcDWORD   m_relproc;      // relative jmpBOOL Init(DWORD_PTR proc, void* pThis){m_mov = 0x042444C7;  //C7 44 24 0Cm_this = PtrToUlong(pThis);m_jmp = 0xe9;m_relproc = DWORD((INT_PTR)proc - ((INT_PTR)this+sizeof(_stdcallthunk)));   // write block from data cache andFlushInstructionCache(GetCurrentProcess(), this, sizeof(_stdcallthunk));    //  flush from instruction cachereturn TRUE;}
...
};
#pragma pack(pop)

WindowProc处理如下:

[cpp] view plaincopy print?

template <class TBase, class TWinTraits>
LRESULT CALLBACK CWindowImplBaseT< TBase, TWinTraits >::WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
CWindowImplBaseT< TBase, TWinTraits >* pThis = (CWindowImplBaseT< TBase, TWinTraits >*)hWnd;//hwnd转换成CWindowImplBaseT指针
...
BOOL bRet = pThis->ProcessWindowMessage(pThis->m_hWnd, uMsg, wParam, lParam, lRes, 0);//调用对应的窗体类的ProcessWindowMessage处理函数
...
}

template <class TBase, class TWinTraits>
LRESULT CALLBACK CWindowImplBaseT< TBase, TWinTraits >::WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{CWindowImplBaseT< TBase, TWinTraits >* pThis = (CWindowImplBaseT< TBase, TWinTraits >*)hWnd;//hwnd转换成CWindowImplBaseT指针...BOOL bRet = pThis->ProcessWindowMessage(pThis->m_hWnd, uMsg, wParam, lParam, lRes, 0);//调用对应的窗体类的ProcessWindowMessage处理函数...
}

可知在具体的窗口过程函数中， 将hWnd转换成对应的窗口类，接着调用窗口类的ProcessWindowMessage调用对应的窗体类处理函数。
每个窗体类都有ProcessWindowMessage函数，它使用一组宏定义如下:

[cpp] view plaincopy print?

BEGIN_MSG_MAP(CMainFrame)
MESSAGE_HANDLER(WM_CREATE, OnCreate)
...
END_MSG_MAP()

BEGIN_MSG_MAP(CMainFrame)MESSAGE_HANDLER(WM_CREATE, OnCreate)...
END_MSG_MAP()

展开显示如下:

[cpp] view plaincopy print?

#define BEGIN_MSG_MAP(theClass) \
public: \
BOOL ProcessWindowMessage(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, LRESULT& lResult, DWORD dwMsgMapID = 0) \
{ \
BOOL bHandled = TRUE; \
(hWnd); \
(uMsg); \
(wParam); \
(lParam); \
(lResult); \
(bHandled); \
switch(dwMsgMapID) \
{ \
case 0:
#define MESSAGE_HANDLER(msg, func) \
if(uMsg == msg) \
{ \
bHandled = TRUE; \
lResult = func(uMsg, wParam, lParam, bHandled); \
if(bHandled) \
return TRUE; \
}

#define BEGIN_MSG_MAP(theClass) \
public: \BOOL ProcessWindowMessage(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, LRESULT& lResult, DWORD dwMsgMapID = 0) \{ \BOOL bHandled = TRUE; \(hWnd); \(uMsg); \(wParam); \(lParam); \(lResult); \(bHandled); \switch(dwMsgMapID) \{ \case 0:#define MESSAGE_HANDLER(msg, func) \if(uMsg == msg) \{ \bHandled = TRUE; \lResult = func(uMsg, wParam, lParam, bHandled); \if(bHandled) \return TRUE; \}

其实就是 宏定义的switch case结构。

至此整个过程如下:

1.Create中指定统一的窗口过程StartWindowProc

2.StartWindowProc第一次响应时完成hwnd和CWndImpl的映射绑定，设置响应函数为WindowProc

3.WindowProc中转hwnd为CWndImpl*，调用对应类的ProcessWindowMessage分发处理消息

4.BEGIN_MSG_MAP简化switch case结构，在每个窗口类中分发处理

总之封装窗口类需要考虑之前说的三点，搞懂了这三点其他的问题也就迎刃而解了。最后不要嫌我烦，再贴一遍我一直强调的重点，牢记这三点，看相应的框架封装过程大同小异:

1.怎么将不同的窗口过程勾到一起

2.同一窗口过程中怎样将不同的hwnd消息分发给对应的CWnd类去处理响应

3.最后，如果CWnd拿到了消息，怎样去简单有效的去处理和响应呢

原创，转载请注明来自http://blog.csdn.net/wenzhou1219