C / C++ / MFC

13-Jun-03 10:24

Hi there, I am having trouble with my dialogues using the cross X in the corner of my dialogue doesn't seem to call PostNcDestroy where I perform clean up of the object. I was expecting the WM_CLOSE message to be generated which calls the default DestroyWindow.

Can anyone explain why it is not being called?
Andy

David Crow13-Jun-03 10:41

David Crow

13-Jun-03 10:41

Interesting. I have a modeless dialog I use in a little app that simply shows a progress bar while the app is running. When I click the 'X', it indeed calls the dialog's PostNcDestroy() function.

John M. Drescher13-Jun-03 10:46

John M. Drescher

13-Jun-03 10:46

I don't think it is called in modal dialogs.

John

andyg.10113-Jun-03 10:51

13-Jun-03 10:51

I don't understand it, I stepped through some of the example code in Nishants tutorial and closing the dialogue with the X definitely calls PostNcDestroy, however it doesn't in mine, despite the fact that clicking the X sends the WM_CLOSE message, which I think should call destroy window. I'm confused, the only difference I can see in my code is that I call ShowWindow in the constructor of my dialogue, and not in the external code. ??

Andy
Frown | :-(

Still confused

John M. Drescher13-Jun-03 10:54

John M. Drescher

13-Jun-03 10:54

Is your dialog modeless then?

John

andyg.10113-Jun-03 10:58

13-Jun-03 10:58

It's definetly modeless, I create a new dialogue like this

if(!m_pDlgComms) // check to see if the dialogue exists
		{
		m_pDlgComms = new CCommsDlg(this);

etc
which is then constructed like this

CCommsDlg::CCommsDlg(CWnd* pParent /*=NULL*/)
	: CDialog(CCommsDlg::IDD, pParent)
{
	//{{AFX_DATA_INIT(CCommsDlg)
	m_sCommsInput = _T("");
	m_sCommsOutput = _T("");
	//}}AFX_DATA_INIT
	if (Create(CCommsDlg::IDD, pParent))
	{ 
	m_pParent = pParent;
	ShowWindow(SW_SHOW);
	}
}

and here is the PostNcDestroy which is called whenever I force a destroy window using a button for example

void CCommsDlg::PostNcDestroy() 
{
	// TODO: Add your specialized code here and/or call the base class
	CDialog::PostNcDestroy();
	if(m_pParent)
	{	
			
		((CBuggycontrolappView*)m_pParent)->m_pDlgComms			= NULL;
		((CBuggycontrolappView*)m_pParent)->m_nCommsToggleState = 0;
	}
	delete this;
}

but not when I use the cross. Even though there is a WM_CLOSE message
Andy

John M. Drescher13-Jun-03 11:09

John M. Drescher

13-Jun-03 11:09

Ok, I understand your problem but I have not seen this in the past. Do you have code for OnCancel() ? Destroying the window with the X button should call OnCancel().

John

Toni7813-Jun-03 18:01

Toni78

13-Jun-03 18:01

When WM_CLOSE is sent, you need to send call DestroyWindow()
For example:

CCommsDlg::OnClose()
{
     DestroyWindow();
}

This is how you close a modeless dialog. When you call DestroyWindow() then of course you will get to
PostNcDestroy().

// Afterall I realized that even my comment lines have bugs

andyg.10113-Jun-03 22:21

13-Jun-03 22:21

Hello again guys
I've solved the problem I think. I put in the handler for WM_CLOSE, and the following code

void CCommsDlg::OnClose() 
{	
	CDialog::OnClose();
	
	DestroyWindow();
}

This now works fine, doing exactly what I want. Previously the code I had used was

void CCommsDlg::OnClose() 
{	
        DestroyWindow();

	CDialog::OnClose();
	
}

which gave me the exception. I'm still not sure why though no doubt one of you guys can inform me and I'm still puzzled by the fact that the code given in Nishants example in the dialogues section makes no call to OnClose at all and still calls PostNcDestroy. However now my code works I'm a happy man Smile | :)

though it'd be better if I understood why!

Cheers
Andy

OnDestroy called for base class first...

Toni7813-Jun-03 23:05

Toni78

13-Jun-03 23:05

As Nishant explains in his article a modal dialog makes a call to DestroyWindow() and as a result to PostNcDestroy().
But in your example you are building a modeless dialog and Windows is very specific about this case. You need to call DestroyWindow() to close a modeless dialog. Why? I don't know. This decision was made by windows. I will do a little bit of investigating though to find out. However, in this case OnClose() doesn't generate an WM_DESTROY message afterwards.
And by the way this part of your code
DestroyWindow();
CDialog::OnClose();
generates an exception because you are sending a WM_CLOSE message to a window that doesn't exist.

// Afterall I realized that even my comment lines have bugs

Miszou13-Jun-03 8:24

Miszou

13-Jun-03 8:24

I have a hierarchy of ListCtrl-derived classes. Everything is working fine, except when OnDestroy is called, it seems to be called in the wrong order, for an object of type CList2:

eg.

class CList1 : public CListCrtl
{
    // OnDestroy called here first
}
 
class CList2 : public CList1
{
    // OnDestroy called here second
}

Am I missing something really obvious here, or is this correct?

There are 10 kinds of people - those that get binary and those that don't.

Re: OnDestroy called for base class first...

valikac13-Jun-03 9:39

valikac

13-Jun-03 9:39

How many objects did you instantiate? What were they?

Kuphryn

Re: OnDestroy called for base class first...

Miszou13-Jun-03 9:49

Miszou

13-Jun-03 9:49

kuphryn wrote:
ForumVisual C++
Subject:Re: OnDestroy called for base class first...
Sender:kuphryn
Date:15:39 13 Jun '03

How many objects did you instantiate? What were they?

Only one, the last one in the hierarchy.

I think I've found my problem - it all comes down to a design that didn't take into account the customers next move... Dead | X|

Basically, I'm trying to fit a square peg in a round hole, and it isn't working at all.

Thanks for replying anyway... Smile | :)

There are 10 kinds of people - those that get binary and those that don't.

problem with passing STL variables across the DLL boundaries

Anonymous13-Jun-03 7:56

Re: problem with passing STL variables across the DLL boundaries

13-Jun-03 7:56

I have a DLL called exceptions.

Now, if I add STL string parameters to its parameter list, my code crashes after entering into the code and after the code is complete....

i.e.
dll file:

class dll_export(delspec) CExcpetions
{
CExceptions();
CExceptions(std::string str);
}

cpp files

using namespace std;

CExceptions::CExceptions()
{
}

CExceptions::CExceptions(string str)
{
/// do something
}

///the calling exe

if( i == 1)
throw CException ("Hello");

As soon as it exits the constructor method,it throws an error.

Any ideas?

C^hris L^osinger13-Jun-03 9:23

C^hris L^osinger

13-Jun-03 9:23

see the MSDN. there are a couple of STL + DLL articles there.

these two in particular might be helpful:
Q172396
Q168958

-c

To vote with no response is to follow the way of the coward.

Re: problem with passing STL variables across the DLL boundaries

Anonymous13-Jun-03 12:05

Re: problem with passing STL variables across the DLL boundaries

13-Jun-03 12:05

It seems to work with vector and maps, but when I try the following with strings it doens't compile:

#ifdef EXP_STL
# define DECLSPECIFIER __declspec(dllexport)
# define EXPIMP_TEMPLATE
#else
# define DECLSPECIFIER __declspec(dllimport)
# define EXPIMP_TEMPLATE extern
#endif

EXPIMP_TEMPLATE template class DECLSPECIFIER std::vector<int>; -- good
EXPIMP_TEMPLATE template class DECLSPECIFIER std::vector<char>; -- good
EXPIMP_TEMPLATE template class DECLSPECIFIER std::string; --fails to compile

Gives the following error:

error C2242: typedef name cannot follow class/struct/union

Anonymous13-Jun-03 12:10

Re: problem with passing STL variables across the DLL boundaries

13-Jun-03 12:10

actually an interesting observation.

If I pass string by value (i.e void method (std::string x), it crashes.
If I pass string by reference (i.e. void method (const std::string & x),it does not crash.

take care

Anonymous15-Jun-03 17:01

15-Jun-03 17:01

Assuming that you are using Visual Studio 6, download the patches to the STL it shipped with from www.dinkumware.com.

reading file 's header

pnpfriend13-Jun-03 7:18

pnpfriend

13-Jun-03 7:18

Every files has header which contains all information about the file.

Is there any function that read files' header.

Can I tell which application file to use to print/view the file base on the information of the file??

for example, I craeted test.txt file using notepad. then I rename the file as temp.t.
Is there any function to tell temp.t can open with notepad??

David Crow13-Jun-03 7:29

David Crow

13-Jun-03 7:29

pnpfriend wrote:
Every files has header which contains all information about the file.

Not necessarily. It depends on the application that was used to create the file.

pnpfriend wrote:
Is there any function that read files' header.

Not a function per se, but there are a plethora of utility-like applications that do this. They're usually created on as as-needed basis.

pnpfriend wrote:
Is there any function to tell temp.t can open with notepad??

FindExecutable()

pnpfriend13-Jun-03 8:33

pnpfriend

13-Jun-03 8:33

<br />
Not a function per se, but there are a plethora of utility-like applications that do this. They're usually created on as as-needed basis.

can you explain it to me again please.
What about By_HANDLE_FILE_INFORMATION structure?? nNumberOfLinks seem likes what I need.. but I dont' know how to use it..

Thank

David Crow13-Jun-03 8:41

David Crow

13-Jun-03 8:41

pnpfriend wrote:
nNumberOfLinks seem likes what I need...

I doubt it, but here's an example:

HANDLE hf;
BY_HANDLE_FILE_INFORMATION bhi;

hf = CreateFile("somefile", GENERIC_READ, FILE_SHARE_READ|FILE_SHARE_WRITE, NULL, FILE_ATTRIBUTE_NORMAL, NULL);

if (INVALID_HANDLE_VALUE != hf)
{
   if (GetFileInformationByHandle(hf, &bhi) == TRUE)
      printf("Links = %lu\n", bhi.nNumberOfLinks);

   CloseHandle(hf);
}