Re: Why does this cause "data abort" ?

From:
"Alexander Nickolov" <agnickolov@mvps.org>
Newsgroups:
microsoft.public.vc.language
Date:
Thu, 25 Oct 2007 11:31:36 -0700
Message-ID:
<#nvkrUzFIHA.4476@TK2MSFTNGP06.phx.gbl>
This will probably work, but beware that WM_CREATE is not
the first message sent to the window. WM_NCCREATE has
that honor I believe. Consequently, it can't be handled in the
class' message map, e.g. you can't implement your own borders.

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@mvps.org
MVP VC FAQ: http://vcfaq.mvps.org
=====================================

"Ben Voigt [C++ MVP]" <rbv@nospam.nospam> wrote in message
news:OlO6jUoFIHA.1184@TK2MSFTNGP04.phx.gbl...

"Lisa Pearlson" <no@spam.plz> wrote in message
news:OrgRWwmFIHA.4196@TK2MSFTNGP04.phx.gbl...

I'm using the SetWindowLong and GetWindowLong like so:

class MyWnd
{
   BOOL Create(..)
   {
   m_hWnd = CreateWindow( .... );
   SetWindowLong(hWnd, GWL_USERDATA, (LONG) hWnd);
   }

   virtual OnCreate(LPCREATESTRUCT lpcs)
   {
           return 0;
   }

   LRESULT OnMessage(MSG msg, WPARAM w, LPARAM l)
   {
           switch (msg)
           {
           case WM_CREATE:
                   return OnCreate( (LPCREATESTRUCT) lParam);
           }
   }
}

in WndProc I do:

LRESULT WndProc(HWND hWnd, MSG msg, WPARAM w, LPARAM l)
{
   MyWnd* pWnd = reinterpret_cast<MyWnd*>( GetWindowLong(hWnd,
GWL_USERDATA);
   return pWnd->OnMessage(msg, w, l);
}

The problem with this is construction is that WM_CREATE will never get
called properly because SetWindowLong occurs AFTER window has been
created, and I think WM_CREATE is sent just before..

So not sure how to solve this problem..


The static WndProc needs to handle WM_CREATE itself.

LRESULT WndProc(HWND hWnd, MSG msg, WPARAM wParam, LPARAM lParam)
{
  MyWnd* pWnd;
   if (msg == WM_CREATE) {
       const CREATESTRUCT const* pCS = (const CREATESTRUCT const*)lParam;
       pWnd = reinterpret_cast<MyWnd*>(pCS->lpCreateParams);
       SetWindowLongPtr(hWnd, GWL_USERDATA, pWnd);
   }
   else
       pWnd = reinterpret_cast<MyWnd*>( GetWindowLongPtr(hWnd,
GWL_USERDATA);
  return pWnd->OnMessage(msg, wParam, lParam);
}

Pass the "this" pointer as the last parameter of CreateWindow(Ex)

Lisa

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