Q: How to Use PostAppMessage( ) to Control Another App?

WnDBSoft@aol.com
Friday, October 18, 1996

Environment: Visual C++ 1.52c, Windows 3.1
Reply-To: mfc-l@netcom.com, WnDBSoft@gnn.com

I would like to send Windows messages to another application using
PostAppMessage( ). The documentation states that PostAppMessage( ),"posts
(places) a message in the message queue of the given application (task)." 

Here's the scoop. I know the path of the application I want to send messages
to.

What I need is its task handle.  Using the path, could anyone please tell me
how to get the application's HTASK so I can send it messages using
PostAppMessage( )?  This other application which I want to control is an MFC
application written with version 2.5x of the library.

Thank you very much for your help!!!

Sincerely,
Brian Hart
WnDBSoft Software International
http://members.aol.com/wndbsoft/wndbsoft.htm

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Jerry Coffin -- jcoffin@taeus.com
Monday, October 21, 1996

[Mini-digest: 7 responses]

At 07:25 PM 10/18/96 -0400, you wrote:
>Environment: Visual C++ 1.52c, Windows 3.1
>Reply-To: mfc-l@netcom.com, WnDBSoft@gnn.com
>
>I would like to send Windows messages to another application using
>PostAppMessage( ). The documentation states that PostAppMessage( ),"posts
>(places) a message in the message queue of the given application (task)." 
>
>Here's the scoop. I know the path of the application I want to send messages
>to.
>
>What I need is its task handle.  Using the path, could anyone please tell me
>how to get the application's HTASK so I can send it messages using
>PostAppMessage( )?  This other application which I want to control is an MFC
>application written with version 2.5x of the library.

Generally if you want to post to another app, you don't want to use
PostAppMessage; generally you still want to post to the message queue of the
other app's main window, in which case you still use PostMessage.  

To use PostMessage, you want to find the handle of its main window.  The
path to the executable won't help you much; instead you need to know the
class and title of its main window.  From the sound of things, you've
written the program being controlled, and you may want to recompile it,
specifying your own name for the window class; by default MFC specifies one
itself, but it may be easier for you to find if you specify your own.

-----From: CHOPINET Ludovic 

With the window's name or window's class, you can retreive the HWND with
::FindWindow(LPCSTR, LPCSTR)
and the call ::GetWindowTask(HWND) to retreive the HTASK associated with
this window.

These functions are obsoletes or deleted under WIN32 !!

Ludovic CHOPINET
E-mail : lchopinet@normand-info.fr
WEB : http://www.normand-info.fr/


-----From: David.Lowndes@bj.co.uk

Brian,

I don't believe that knowing the path of the application's EXE file is the right
starting point, unless your application is starting that application, as there is no
HTASK unless the other application is running.

You need to identify a window handle of a running instance of the application
using FindWindow, then from there you can get a HTASK using GetWindowTask.
However once you've got the HWND, you may be better off using PostMessage
rather than PostAppMessage anyway.

Dave Lowndes
-----From: Mario Contestabile

In one of your 16-bit CWnd objects, you could do
CWnd *a = FindWindow("class", "window");
if(a)
  HTASK b = ::GetWindowTask(a.GetSafeHwnd());
if(b)
  PostAppM....

mcontest@universal.com


-----From: "Brian V. Zaino (516) 434-6278" 

To get the task handle, you will need to use toolhelp.dll's 
TaskFirst and TaskNext functions.  To find the task handle,
you must know the module name, not the path.  The code 
would look something like this:

#include 

HTASK GetTask(CString csModuleName)
{
   TASKENTRY te;
   te.dwSize = sizeof(te);

   /* search the module list */
   if (TaskFirst(&te))
   {
      do
      {
         /* Module found? */
         if (csModuleName == te.szModule) 
            return te.hTask;
      }
      while (TaskNext(&te));
   }
   return NULL;
}

I hope this helps,
Brian

-----From: rwagner 

Environment: Visual C++ 1.52c, Windows 3.1

Brian wrote:

> I would like to send Windows messages to another > application using 
PostAppMessage( ). 

In each app to which you wish to send messages, make a call to _getPID() just 
before you register the window class.  This works in MFC just fine, here's the 
override:

BOOL IFSDIFrame::PreCreateWindow(CREATESTRUCT& cs)
{
    sprintf( pid, "%X", _getpid() ); 
    CString windowClass = (LPCTSTR)pid; 
    if( ! CFrameWnd::PreCreateWindow(cs) )
        return FALSE;
    WNDCLASS wndClass;
    memset( &wndClass, 0x0, sizeof(WNDCLASS) );
    ASSERT( ::GetClassInfo(AfxGetInstanceHandle(), cs.lpszClass, &wndClass) );
    cs.lpszClass = (LPCTSTR)pid;
    wndClass.lpszClassName = (LPCTSTR)pid;
    ASSERT( AfxRegisterClass(&wndClass) ); // stub if class already registered.
    return CFrameWnd::PreCreateWindow( cs );
...
}

I then make a call to ::FindWindow( windowClass, NULL) from any app and get back
a handle to the target window, and then I can access it in any manner that 
requires
a handle.

This may not be exactly what you want.  It works for me because I can juggle 
any number of instances of the same app this way.  You may want to register the 
window class with some unique identifier instead.

I do this routinely in win32, this should still work in Ancient Windows.

Cheers
Rob
-----From: "elie (e.e.) bensaci" 


Hi there,

What you need, is to call the 

static CWnd* PASCAL FindWindow( LPCTSTR lpszClassName, LPCTSTR lpszWindowName );
  
This will give you a handle to the application that you're looking for, then use this 
handle to post your message. something like this: pHandle->PostMessage( ...), and you 
should process the message in the application that receives your message.

Hope this help.

Elie.

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