OpenEuphoria

2. Re: onEvent ??

• Posted by David Cuny <dcuny at LANSET.COM> Jul 27, 1999
• 504 views

Bernie wrote:

>  I am having trouble trying to figure out how you set
> the callback for winProc to monitor events on main
> window. I don't think that you automatically set it up
> in WinMain will you please tell me what I have to do;
> onEvent doesn't seem to work in the main window ??

No, onEvent works for the main window. Perhaps a tour through how Win32Lib
sets up the callbacks might clarify things.

The variable WndProcAddress holds the address of the single callback that
Win32Lib uses. It is assigned to windows is the createWindow() routine with
this snippet of code:

   store( wndClassEx, winExProc, WndProcAddress )

It replaces the default handler for controls in:

    window_func[id] = c_func( xGetWindowLong,
        { window_handle[id], GWL_WndProc, WndProcAddress } )

The callback is assigned to a Euphoria routine in get_proc_address(), which
assigns it to the WndProc routine. If you look at WndProc, the first thing
it tries to do is find the window handle:

   id = find( myHwnd, window_handle )

A few steps later, it checks to see if you set the onEvent hook. (The test
should actually read > -1, not > 0 ):

   if onEvent[ id ] > 0 then
      -- call routine
      call_proc( onEvent[id], { iMsg, wParam, lParam } )
   end if

The only Win32 controls that don't use this callback are Menu and MenuItem.
For these, I trap the WM_COMMAND sent by Win32. In these cases, the menu id
is passed in the wParam.

-- David Cuny