Intercep Messages to Windows, or View Them

**maththeorylvr** · 02-17-2005

Hello. I am using C and Win32 API. I'm trying to find a way to view the message queue of a certain window that receives text and would like to see the text before it shows up on the window. My idea is to look at all the WM_CHAR messages a certain window receives, and then convert those to strings.
Any suggestions on how to start? I know the handle of the window, and can get the thread that it belongs to.

**Ken Fitlike** · 02-19-2005

You need to be more specific.

Is this your application?
If it's not your application (and you don't have the source code) then you should explain why you want to do this so that we know you are not in breach of good conduct (forum guidelines, rule 6).
Is the window in question a system window class (eg. an 'edit' control)?

**maththeorylvr** · 02-19-2005

it is my application. I'm trying to stream the contents of an Edit Control box.

**adrianxw** · 02-19-2005

Sounds like what you want to do is a bit of sub-classing, have a play with this. NewEditProc() receives all the messages and either processes them, or passes them on unmodified to the original procedure.

Code:

#include <windows.h>

LRESULT CALLBACK WindowFunc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK NewEditProc(HWND, UINT, WPARAM, LPARAM);

HINSTANCE hInst;
WNDPROC OriginalEditProc;

int WINAPI WinMain(HINSTANCE hThisInst, HINSTANCE hPrevInst, 
                   LPSTR Args, int WinMode)
{
    HWND hWnd;
    MSG Message;
    WNDCLASSEX Wcl;

    hInst = hThisInst;
    
    Wcl.cbSize = sizeof(WNDCLASSEX);    
    Wcl.hInstance = hThisInst;
    Wcl.lpszClassName = "Window";
    Wcl.lpfnWndProc = WindowFunc; 
    Wcl.style = 0;  
    Wcl.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    Wcl.hIconSm = LoadIcon(NULL, IDI_WINLOGO);
    Wcl.hCursor = LoadCursor(NULL, IDC_ARROW);
    Wcl.lpszMenuName = NULL; 
    Wcl.cbClsExtra = 0; 
    Wcl.cbWndExtra = 0;
    Wcl.hbrBackground = (HBRUSH) GetStockObject(LTGRAY_BRUSH); 
    
    if(!RegisterClassEx(&Wcl)) return 0;
    
    hWnd = CreateWindow(
        "Window", 
        "Window",
        WS_OVERLAPPEDWINDOW, 
        CW_USEDEFAULT, 
        CW_USEDEFAULT, 
        CW_USEDEFAULT, 
        CW_USEDEFAULT, 
        HWND_DESKTOP, 
        NULL, 
        hThisInst, 
        NULL 
        );
    
    ShowWindow(hWnd, WinMode);
    UpdateWindow(hWnd);

    while(GetMessage(&Message, NULL, 0, 0))
    {
        TranslateMessage(&Message); 
        DispatchMessage(&Message);
    }
    return Message.wParam;
}

LRESULT CALLBACK WindowFunc(HWND hWnd,UINT Message,WPARAM wParam,LPARAM lParam)
{
    static HWND hEditBox;
    
    switch(Message)
    {
    case WM_CREATE:
        hEditBox = CreateWindowEx(0,
                                  "EDIT",
                                  NULL,
                                  WS_CHILD | WS_VISIBLE | WS_BORDER,
                                  10,
                                  10,
                                  300,
                                  20,
                                  hWnd,
                                  (HMENU) 500,
                                  hInst,
                                  NULL);
        OriginalEditProc = (WNDPROC) SetWindowLong(hEditBox,
                                                   GWL_WNDPROC,
                                                   (LONG) NewEditProc);

        SetFocus(hEditBox);
        break;
    case WM_DESTROY:
        SetWindowLong(hEditBox,
                      GWL_WNDPROC,
                      (LONG) OriginalEditProc);
        DestroyWindow(hEditBox);
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, Message, wParam, lParam);
    }
    return 0;
}

LRESULT CALLBACK NewEditProc(HWND hWnd,UINT Message,WPARAM wParam,LPARAM lParam)
{
    const int TAB = '\x09';
    const int CR = '\x0d';
    const int ESC = '\x1b';
    
    if (Message == WM_CHAR)
    {
        if (wParam == TAB)
        {
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) '<',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) 'T',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) 'A',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) 'B',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) '>',
                           lParam);
            return 0;
        }
        else if (wParam == CR)
        {
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) '<',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) 'C',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) 'R',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) '>',
                           lParam);
            return 0;
        }
        else if (wParam == ESC)
        {
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) '<',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) 'E',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) 'S',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) 'C',
                           lParam);
            CallWindowProc(OriginalEditProc,
                           hWnd,
                           Message,
                           (WPARAM) '>',
                           lParam);
            return 0;
        }
    }

    return CallWindowProc(OriginalEditProc,
                          hWnd,
                          Message,
                          wParam,
                          lParam);
}

**maththeorylvr** · 02-19-2005

Thanks for all the suggestions. What I did, to read the Edit Control Contents line-by-line, is the following. The Edit Control is to a chat program of mine, so the data streams in at a certain rate. Since my bot doesnt need any of the statements before the current one, I just delete the line, and stay on the top line.:

Code:

 
 
// hwnd = edit control window
// len = length of top line

len = SendMessage(hwnd, EM_LINELENGTH, 0, 0 );

SendMessage(hwnd, WM_GETTEXT, len + 1, (LPARAM) &data);
 
//delete the line
SendMessage(hwnd, WM_SETTEXT, 0, (LPARAM)(LPCTSTR)text);

//all chat stays on the top line, which is okay for the bot's sake
 data[len + 1] = '\0';

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