子类化的SDK方式

窗口子类化

定义

替换窗体的窗口处理过程的操作，叫做”窗口子类化”

子类化的目的 : 控制窗口消息.

子类化的好处 ：不需要得到, 参考, 修改原始窗口处理过程源码.

注意事项

Subclass(子类化)只能用在本进程.

如果要用在其它进程，必须将新的窗口处理过程实现注入目标进程，然后才能进行窗口子类化.

子类化只能做一次, 被子类化的窗口在销毁前，必须将原始窗口处理过程还原，保证代码运行的安全性和稳定性.

可采用的API

SetWindowLong 常见, 在开源工程中经常使用这个API, 进行子类化.

SetClassLong 功能更全, 在开源工程中不常见.

Demo

// SubClassSDK.cpp : Defines the entry point for the application.
//

#include "stdafx.h"
#include <assert.h>
#include "resource.h"

#define MAX_LOADSTRING 100

// Global Variables:
HINSTANCE hInst;								// current instance
TCHAR szTitle[MAX_LOADSTRING];								// The title bar text
TCHAR szWindowClass[MAX_LOADSTRING];								// The title bar text

// Foward declarations of functions included in this code module:
ATOM				MyRegisterClass(HINSTANCE hInstance);
BOOL				InitInstance(HINSTANCE, int);
LRESULT CALLBACK	WndProc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK	About(HWND, UINT, WPARAM, LPARAM);

WNDPROC g_pOrg_WindowProc_EditNum = NULL;
LRESULT CALLBACK WindowProc_EditNum(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
);

int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
 	// TODO: Place code here.
	MSG msg;
	HACCEL hAccelTable;

	// Initialize global strings
	LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
	LoadString(hInstance, IDC_SUBCLASSSDK, szWindowClass, MAX_LOADSTRING);
	MyRegisterClass(hInstance);

	// Perform application initialization:
	if (!InitInstance (hInstance, nCmdShow)) 
	{
		return FALSE;
	}

	hAccelTable = LoadAccelerators(hInstance, (LPCTSTR)IDC_SUBCLASSSDK);

	// Main message loop:
	while (GetMessage(&msg, NULL, 0, 0)) 
	{
		if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg)) 
		{
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}
	}

	return msg.wParam;
}



//
//  FUNCTION: MyRegisterClass()
//
//  PURPOSE: Registers the window class.
//
//  COMMENTS:
//
//    This function and its usage is only necessary if you want this code
//    to be compatible with Win32 systems prior to the 'RegisterClassEx'
//    function that was added to Windows 95. It is important to call this function
//    so that the application will get 'well formed' small icons associated
//    with it.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
	WNDCLASSEX wcex;

	wcex.cbSize = sizeof(WNDCLASSEX); 

	wcex.style			= CS_HREDRAW | CS_VREDRAW;
	wcex.lpfnWndProc	= (WNDPROC)WndProc;
	wcex.cbClsExtra		= 0;
	wcex.cbWndExtra		= 0;
	wcex.hInstance		= hInstance;
	wcex.hIcon			= LoadIcon(hInstance, (LPCTSTR)IDI_SUBCLASSSDK);
	wcex.hCursor		= LoadCursor(NULL, IDC_ARROW);
	wcex.hbrBackground	= (HBRUSH)(COLOR_WINDOW+1);
	wcex.lpszMenuName	= (LPCSTR)IDC_SUBCLASSSDK;
	wcex.lpszClassName	= szWindowClass;
	wcex.hIconSm		= LoadIcon(wcex.hInstance, (LPCTSTR)IDI_SMALL);

	return RegisterClassEx(&wcex);
}

//
//   FUNCTION: InitInstance(HANDLE, int)
//
//   PURPOSE: Saves instance handle and creates main window
//
//   COMMENTS:
//
//        In this function, we save the instance handle in a global variable and
//        create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   HWND hWnd;

   hInst = hInstance; // Store instance handle in our global variable

   hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);

   if (!hWnd)
   {
      return FALSE;
   }

   ShowWindow(hWnd, nCmdShow);
   UpdateWindow(hWnd);

   return TRUE;
}

//
//  FUNCTION: WndProc(HWND, unsigned, WORD, LONG)
//
//  PURPOSE:  Processes messages for the main window.
//
//  WM_COMMAND	- process the application menu
//  WM_PAINT	- Paint the main window
//  WM_DESTROY	- post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	int wmId, wmEvent;
	PAINTSTRUCT ps;
	HDC hdc;
	TCHAR szHello[MAX_LOADSTRING];
	LoadString(hInst, IDS_HELLO, szHello, MAX_LOADSTRING);

	switch (message) 
	{
		case WM_COMMAND:
			wmId    = LOWORD(wParam); 
			wmEvent = HIWORD(wParam); 
			// Parse the menu selections:
			switch (wmId)
			{
				case IDM_ABOUT:
				   DialogBox(hInst, (LPCTSTR)IDD_ABOUTBOX, hWnd, (DLGPROC)About);
				   break;
				case IDM_EXIT:
				   DestroyWindow(hWnd);
				   break;
				default:
				   return DefWindowProc(hWnd, message, wParam, lParam);
			}
			break;
		case WM_PAINT:
			hdc = BeginPaint(hWnd, &ps);
			// TODO: Add any drawing code here...
			RECT rt;
			GetClientRect(hWnd, &rt);
			DrawText(hdc, szHello, strlen(szHello), &rt, DT_CENTER);
			EndPaint(hWnd, &ps);
			break;
		case WM_DESTROY:
			PostQuitMessage(0);
			break;
		default:
			return DefWindowProc(hWnd, message, wParam, lParam);
   }
   return 0;
}

// Mesage handler for about box.
LRESULT CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
    HWND hWndEditNum = NULL;

    switch (message)
    {
    case WM_INITDIALOG: 
        {
            hWndEditNum = ::GetDlgItem(hDlg, IDC_EDIT_NUM);
            assert(NULL != hWndEditNum);
            if (NULL == g_pOrg_WindowProc_EditNum) {
                g_pOrg_WindowProc_EditNum = (WNDPROC)SetWindowLong(
                    hWndEditNum,
                    GWL_WNDPROC, 
                    (LONG)WindowProc_EditNum);
                assert(NULL != g_pOrg_WindowProc_EditNum);
            }
        }
        return TRUE;

    case WM_DESTROY:
        {
            if (NULL != g_pOrg_WindowProc_EditNum) {
                hWndEditNum = ::GetDlgItem(hDlg, IDC_EDIT_NUM);
                SetWindowLong(
                    hWndEditNum, 
                    GWL_WNDPROC, 
                    (LONG)g_pOrg_WindowProc_EditNum);
                g_pOrg_WindowProc_EditNum = NULL;
            }
        }
        break;
        
    case WM_COMMAND:
        if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL) 
        {
            EndDialog(hDlg, LOWORD(wParam));
            return TRUE;
        }
        break;
    }
    return FALSE;
}

LRESULT CALLBACK WindowProc_EditNum(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
  ) {
    BOOL isNum = FALSE;
    TCHAR c = TEXT('');
    
    if (WM_CHAR == uMsg) {
        c = (TCHAR)wParam;
        isNum = (c >= TEXT('0')) && (c <= TEXT('9'));
        if (!isNum) {
            return 0;
        }
    }

    if (NULL != g_pOrg_WindowProc_EditNum) {
        return g_pOrg_WindowProc_EditNum(hwnd, uMsg, wParam, lParam);
    }

    return 0;
}