modeless vs modal dialog boxes

Gene Sewell -- genes@fast.net
Friday, May 31, 1996

Environment: WinNT(Version 3.51 - build 1057: Service Pack 4) and VC++ 4.1  32Mb

I have a problem....

I am part of a small development team.  I implemented a modeless dialog box
that was rather complex.  (I don't think that has anything to do with the
problem....)

My problem is that after completing the task, I merged the working code with
the programming team.  I am sure that the merge didn't affect any of my
dialog box code.  Yet, during testing, my dialog box no longer was created.
What happens is that the main application loses focus (the caption bar is no
longer colored as top window), but no new window comes to the top.  

To prove the dialog code still was working, I converted the call to generate
a modal dialog box.  As soon as I did that the dialog appeared and worked
just fine.  I have left it modal for the time being, but it has to become
modeless quickly.

What I seem unable to figure out is just why I no longer can get my dialog
box code to work as a modeless box.  It worked fine at one point, but now no
longer works.  I do not believe the reason has anything to do with memory or
resource shortages.  During testing, this is the first box I bring up.

Can anyone suggest leads for me to investigate?  As an aside, I would wish
that a future MFC would take some of the mystery out of dialog boxes.  I
would like to have the switch between modal and modeless be a simple style
bit or a member variable option, rather than requiring substantially
different code.

Here's the code for invoking the box:

#ifndef NONMODALWORKS
// this is what I'm using now - it works fine
	LibCardDialog myDlg;
	myDlg.DoModal();
#else
	if ( (mx_LibCardDialog = new LibCardDialog ) )
		if( ! mx_LibCardDialog->Create() )
		{
			delete mx_LibCardDialog;
			mx_LibCardDialog = NULL;
		}
#endif

In my dialog box code:

I used the method suggested by Kruglinski (mx_LibCardDialog->Create() )

BOOL LibCardDialog::Create()
{
    return CDialog::Create(LibCardDialog::IDD);
}


Thanks,

Gene

----
If it weren't for the last minute, nothing would ever get done.

---

Venkateswara Sunkara -- Venkateswara_Sunkara@countrywide.com
Sunday, June 02, 1996

[Mini-digest: 13 responses]

In case if you have not used the visible style( WS_VISIBLE ) in the dialogbox 
template you should use ShowWindow to make it appear. Try calling 
mx_LibCardDialog->ShowWindow(SW_SHOW) after creating the dialog. Hope this 
helps.

Venkateswara Sunkara
-----From: "John W. Podlogar Jr." 


The first thing that I would do is check your app with Spy++ to
see if the window is even being created. If you see it in the list
then check it's geometry values (you may just need to call CenterWindow).

If it doesn't show up in the Spy++ list then check your call to
"Create" make sure you are passing is a valid template resource.

If you seem to be then step into the Create function and see what
it's doing.

You can never beat stepping into the MFC source to see what's happening.
You can debug most problems by doing this.

John W. Podlogar Jr.    The wise man doesn't pose the right answers, 
podlogar@lm.com                         he asks the right questions. 
http://www.lm.com/~podlogar

-----From: Dean McCrory 

It sounds like your dialog box is hidden.  Perhaps it doesn't have
WS_VISIBLE in the resource?  Your best be to these kind of problems is
to *debug the code*.  You can use Spy++ to see if the window for the
dialog is there.  You can use the debugger to verify if your
OnInitDialog is being called, what the Create call is returning, etc.

// Dean

-----From: Marty Fried 

What does the app do after creating your dialog?  Does it continue to
process its messages?  Does it close its main window (m_pMainWnd)?  Doing
that signals the framework to stop processing messages, I believe.

Since your code works as a modal dialog, I'd look at the main app's code
for the problem.

-----From: "Hampton-Smith, Paul" 

I'm not sure about the modal/modeless difference, but I have had an occasion 
when a dialog box, developed on a hi res screen, was simply off-screen on 
the target 640x480 machine.  If this is the problem, alt-tab should get the 
system menu for the box up, at which time you should be able to move it into 
view.  If so, you'd be able to fix the problem with a centre_window method.

Paul Hampton-Smith
-----From: antony@cauchy.miel.mot.com (ANTONISAMY A[MIEL])

	When you merged your application, if you had created the dialog
	resource againg instead of copying from the test app, make sure
	you have the VISIBLE style box checked. Modeless dialogs are
	popuped only if WS_VISIBLE style is used. Otherwise explicit
	ShowWindow(SW_SHOW) has to be used.
	Otherwise I see no problem why your modeless dialog works for
	your test app and not for your main app.

- Antony
antony@miel.mot.com
-----From: Sunitha Kumar 


Probably, you have not made the window visible. That is, in the resource, 
the styles is invisible. Probably, if you look into the resource, you 
might find some answer.
Hope this helps.		Sunitha KumarOn Fri, 31 May 1996, Gene Sewell wrote:

-----From: Kjell Gunnar Tenstad 

I think you must do a call to make the dialog visible, here is what
I do :

BOOL CAlarmPageDlg::DoModeLess(CWnd* pParent)
{
	BOOL bs=CDialog::Create(CAlarmPageDlg::IDD,pParent);
	if(bs)
	    ShowWindow(SW_SHOW);
	return bs;
}

------------------------------oO00Oo-------------------------------
kjellg@albatross.no     Kjell Gunnar Tenstad,
------------------------------oO00Oo-------------------------------
-----From: Gene Sewell 

Thanks for the great input.  You hit the nail right on the head!

I guess what happened is that during the merge, my dialog template lost the
visible style bit (I checked and it's not there.)  Initially, it was there,
so everything worked.

Adding the ShowWindow(SW_SHOW) fixed it right away.  I've since added the
visible style bit again in the resource editor.

Thanks again!

Gene
----
"It is one of the most beautiful compensations of this life that no man 
can sincerely try to help another without helping himself."

	>>>Ralph Waldo Emerson

-----From: Mike Martonfi 

Is the WS_VISIBLE style set in the dialog template?
---------------------
Mike Martonfi
mikem@abelcomputers.com

-----From: Mario Contestabile

I believe the problem resides in the fact that you are calling 
CDialog::Create() from
YourDialog::Create(). 

Try:
mx_LibCardDialog = new LibCardDialog;
LibCardDialog.Create(LibCardDialog::IDD);

//dlg ctor
LibCardDialog::LibCardDialog() : CDialog(LibCardDialog::IDD){
}

and make sure the dialog has the WS_VISIBLE style.

mcontest@universal.com
-----From: Paolo Savelli 

that delete line is wherein lies your problem.  In a modal dialog 
box, you can delete after calling .DoModal(), since your application 
is stuck in the dialog box procedure.  In a modeless dialog box, the 
Create() function is executed, bringing up the window, then your 
program returns from the Create() call and goes on to execute the 
following lines of code, to eventually return control to the main 
message proc. So, in your code you are bringing up the modeless box, 
and then destroying it before you actually see it.

Hope this helps. 

Paolo
-----From: "Peter A. Vanvliet" 

Just a thought...

Have you tried doing a ShowWindow(SW_SHOWNA) on the mx_LibCardDialog?


Peter A. Vanvliet    Houston, Texas    pvanvlie@neosoft.com 
System Analyst, NanoSoft Corporation (http://www.special-events.com)
HALPC C++ SIG Leader 
WWW home page (http://www.special-events.com/cppsig)

---

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