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From: claus.kick on 27 Sep 2009 17:45
On 27 Sep., 22:20, Giuliano Suminsky <yksni...(a)gmail.com> wrote:
> Hi, I  was just trying to create a button( BS_GROUP ) at the WM_CREATE
> of the main window, but it fails..
>
> But when I create it just after create the main window, its fine,
> why?
> Cant I create buttons at the WM_CREATE? Or is just something stupid Im
> missing?
>
*snip*

My guess is that hmainwnd is not valid during WM_CREATE?
From: r_z_aret on 28 Sep 2009 09:26
On Sun, 27 Sep 2009 13:20:22 -0700 (PDT), Giuliano Suminsky
<yksnimus(a)gmail.com> wrote:

>Hi, I was just trying to create a button( BS_GROUP ) at the WM_CREATE
>of the main window, but it fails..
>
>But when I create it just after create the main window, its fine,
>why?
>Cant I create buttons at the WM_CREATE? Or is just something stupid Im
>missing?

I _think_ the HWND for a window is not fully valid until after the
WM_CREATE for that window is fully processed. So you can't create
subwindows while processing WM_CREATE.

I know I create subwindows when I process WM_INITDIALOG.

>
>That works ok:
>
>//*******
>
>hmainwnd = CreateWindow( TEXT("MAINWNDCLASS"), szCaption,
> WS_OVERLAPPEDWINDOW,
> wndrect.left, wndrect.top, wndrect.right, wndrect.bottom,
> NULL, NULL, hInstance, NULL );
>
>
> hbgroupIPDisplay = CreateWindow( TEXT("Button"), TEXT("Your IP"),
> WS_CHILD | WS_VISIBLE | BS_GROUPBOX,
> 50, 50, 160, 160,
> hmainwnd, (HMENU)100, //button ID
> GetModuleHandle(NULL),
> NULL );
>//**********
>
>
>That dont:
>
>//*********
>
>case WM_CREATE:
>
> hbgroupIPDisplay = CreateWindow( TEXT("Button"), TEXT("Your IP"),
> WS_CHILD | WS_VISIBLE | BS_GROUPBOX,
> 50, 50, 160, 160,
> hmainwnd, (HMENU)100, //button ID
> GetModuleHandle(NULL),
> NULL );
>
>
>
>
> return 0;
>
>//***********

-----------------------------------------
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Robert E. Zaret, eMVP
PenFact, Inc.
20 Park Plaza, Suite 400
Boston, MA 02116
www.penfact.com
Useful reading (be sure to read its disclaimer first):
http://catb.org/~esr/faqs/smart-questions.html
From: Markus Schaaf on 28 Sep 2009 09:58
r_z_aret(a)pen_fact.com wrote:

> I _think_ the HWND for a window is not fully valid until after the
> WM_CREATE for that window is fully processed.

No. It is valid, whatever that means. The OP's problem was, that he
(probably) used code like this:

mainWindow = CreateWindow( ... );

So `mainWindow` is not initialized until `CreateWindow` returns. But
the WM_CREATE message will be sent before that. An easy fix is to
initialize the global in the window procedure:

LRESULT CALLBACK mainWindowProc( self, msg, ... )
{
switch( msg )
{
case WM_CREATE:
mainWindow = self;
....
From: claus.kick on 29 Sep 2009 07:37
On 28 Sep., 15:58, Markus Schaaf <msch...(a)elaboris.de> wrote:
> r_z_aret(a)pen_fact.com wrote:
> > I _think_ the HWND for a window is not fully valid until after the
> > WM_CREATE for that window is fully processed.
>
> No.  It is valid, whatever that means.  The OP's problem was, that he
> (probably) used code like this:

A window handle has to be valid, i.e. in exitance before it can be
used.

> So `mainWindow` is not initialized until `CreateWindow` returns.  But
> the WM_CREATE message will be sent before that.  An easy fix is to
> initialize the global in the window procedure:
>
>     LRESULT CALLBACK mainWindowProc( self, msg, ... )
>     {
>         switch( msg )
>         {
>             case WM_CREATE:
>                 mainWindow = self;
>     ....

Could you please explain how this should help?

If you reference a window handle which is the result of a create
window call, this has to be a valid handle, not just in scope?
From: Markus Schaaf on 29 Sep 2009 09:22
claus.kick(a)googlemail.com schrieb:

> A window handle has to be valid, i.e. in exitance before it can be
> used.

I do not get your point. You do not excogitate handles. When you got a
window handle, it refers to a specific window, and is valid until that
window will be destroyed. There is no possibility of getting a window
handle that will become valid later.
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