Re: Access Violation Error - C / C++ / MFC Discussion Boards

Re: How can I make a modeless topmost for the desktop ?

S Douglas18-Oct-05 22:50

18-Oct-05 22:50

yarp wrote:
The code is just basic SetWindowPos:
SetWindowPos(m_hWnd, NULL, 0, 0, 0, 0, HWND_TOPMOST);

Is there a trick or a way to make that modeless topmost ?

Try this instead.

SetWindowPos(&wndTopMost, 0, 0, 0, 0, SWP_NOSIZE);

CWnd::SetWindowPos[^]

DEBUGGING : Removing the needles from the haystack.

Re: How can I make a modeless topmost for the desktop ?

yarp20-Oct-05 6:19

yarp

20-Oct-05 6:19

I found a solution as suggested by Iain. The other ways din't work:
Here's the function that makes it :

void CfrmImg::EnableStayOnTop(bool bDesktop)<br />
{<br />
  // Desktop topmost<br />
  if (bDesktop) {<br />
    ::SetWindowLongPtr(m_hWnd, GWL_HWNDPARENT, NULL);<br />
    ::SetWindowPos(m_hWnd, HWND_TOPMOST, 0, 0, 0, 0,<br />
                   SWP_NOMOVE | SWP_NOSIZE);<br />
  }<br />
  // Application topmost<br />
  else {<br />
    if (::GetParent(m_hWnd)==NULL)<br />
    	::SetWindowLongPtr(m_hWnd, GWL_HWNDPARENT, (LONG_PTR)frmMain->m_hWnd);<br />
    ::SetWindowPos(m_hWnd, HWND_TOPMOST, 0, 0, 0, 0,<br />
                   SWP_NOMOVE | SWP_NOSIZE);<br />
  }<br />
}<br />

I recall this is for a modeless dialog - don't know if it makes sense for modals.
The SetWindowLongPtr with GWL_HWNDPARENT parameter is a dirty hack. MSDN says SetParent should be used instead, but with SetParent it didn't work (I presume I have to change the windows style as suggested by MSDN - this is a later clean up work).
At the moment I'm happy with my stay on top function.

Thanks all for your assistance.

Yarp
http://www.senosoft.com/

Access Violation Error

nripun18-Oct-05 3:50

nripun

18-Oct-05 3:50

I created a dialog class CSchDlg derived from CDialog. The dialog box has a few buttons(radio and checkboxes also) and a list box. Using the class wizard i created member variables of type CButton for all the buttons and of type CListBox for the list box.

Inside the OnInitDialog() i tried the following.
Say m_ctrlButton1 is of type CButton and is the member variable for the radio button with the ID IDC_RADIOBUTTON1

<br />
m_ctrButton1.SetCheck(BST_CHECKED);<br />

The above stmt produced error.

So i changed it to

<br />
CButton *pButton;<br />
pButton = (CButton *) this->GetDlgItem(IDC_RADIOBUTTON1);<br />
pButton->SetCheck(BST_CHECKED);<br />

... and it worked fine.

I tried the same thing for the ListBox also.

<br />
CListBox *pListBox;<br />
pListBox = (CListBox*) this->GetDlgItem(IDC_LISTBOX1);<br />

... but it produced Access Violation Error

What could be the reason?

Why do i have to use GetDlgItem() to set/enable or do anything on the buttons inside the OnInitDlg() but neednt do it in other functions?

Re: Access Violation Error

David Crow18-Oct-05 3:57

David Crow

18-Oct-05 3:57

nripun wrote:
The above stmt produced error.

What error?

nripun wrote:
CButton *pButton;
pButton = (CButton *) this->GetDlgItem(IDC_RADIOBUTTON1);
pButton->SetCheck(BST_CHECKED);

... and it worked fine.

Perhaps it only appeared to work?

nripun wrote:
... but it produced Access Violation Error

Are you trying to do this before CDialog::OnInitDialog() is called?

nripun wrote:
Why do i have to use GetDlgItem() to set/enable or do anything on the buttons inside the OnInitDlg() but neednt do it in other functions?

You don't. GetDlgItem() is rarely, if ever, needed.

"Take only what you need and leave the land as you found it." - Native American Proverb

Re: Access Violation Error

C^hris L^osinger18-Oct-05 4:03

C^hris L^osinger

18-Oct-05 4:03

DavidCrow wrote:
GetDlgItem() is rarely, if ever, needed.

actually, i use it all the time.

Cleek | Image Toolkits | Thumbnail maker

Re: Access Violation Error

David Crow18-Oct-05 4:43

David Crow

18-Oct-05 4:43

Using it and needing it are two different things.

"Take only what you need and leave the land as you found it." - Native American Proverb

Re: Access Violation Error

C^hris L^osinger18-Oct-05 4:50

C^hris L^osinger

18-Oct-05 4:50

indeed. most things are that way.

but, GetDlgItem is very useful.

Cleek | Image Toolkits | Thumbnail maker

Re: Access Violation Error

nripun18-Oct-05 5:21

nripun

18-Oct-05 5:21

DavidCrow wrote:
What error?

Debug Assertion Error
File:afxwin2.inl
Line 590

DavidCrow wrote:
Are you trying to do this before CDialog::OnInitDialog() is called?

I have tried both, b4 and after

I am restating my problem and i will try to be as clear as possible.

Aim is to have the dialog box pop up with a few checkboxes and radiobuttons checked and the listbox be filled.
Using class wizard i assigned the following member variables to the radiobuttons and the list box.

The first radiobutton is IDC_RADIOBUTTON1
The second radiobutton is IDC_RADIOBUTTON2
The listbox is IDC_LISTBOX1
When i open the MemberVariables tab in the ClassWizard i get the following..

ControlIDs Type Member
IDC_RADIOBUTTON1 CButton m_radio1
IDC_RADIOBUTTON1 CButton m_radio2
IDC_LISTBOX1 CListBox m_listbox1

Now when the dialog opens i want hte first radiobutton to be checked, the second radiobutton be disabled and the listbox be filled with certain text.

To achieve the above result i wrote the following code inside the OnInitDialog function.

<br />
m_radio1.SetCheck(BST_CHECKED);<br />
m_radio2.EnableWindow(FALSE);<br />
m_listbox1.AddString(BUFF);<br />

The above code gave the Debug Assertion Error i mentioned in the beginning of the post.

Now i change the above piece of code to

<br />
CButton *pButton;<br />
pButton=(CButton*)this->GetDlgItem(IDC_RADIOBUTTON1);<br />
pButton->SetCheck(BST_CHECKED);<br />
pButton=(CButton*)this->GetDlgItem(IDC_RADIOBUTTON2);<br />
pButton->EnableWindow(FALSE);<br />

..... it actually worked

Then i added the GetDlgItem for te list box

<br />
BOOL CSchDlg::OnInitDialog(){<br />
CDialog::OnInitDialog();<br />
CButton *pButton;<br />
CListBox *pListBox;<br />
pButton=(CButton*)this->GetDlgItem(IDC_RADIOBUTTON1);<br />
pButton->SetCheck(BST_CHECKED);<br />
pButton=(CButton*)this->GetDlgItem(IDC_RADIOBUTTON2);<br />
pButton->EnableWindow(FALSE);<br />
pListBox = (CListBox *)this->GetDlgItem(IDC_TIMETABLELIST);<br />
pListBox->AddString("Hope this works");<br />
<br />

The DoModal() of the Dialog box is done from another class CMySch.
The above piece of code works fine when i DoModal() for the first time.
But after i close the dialog and then again call DoModal from CMySch the following error:
Access violation

comes at pListBox = (CListBox *)this->GetDlgItem(IDC_TIMETABLELIST);

Inside the debug window the following was displayed

Name Value
---- ------
this {SchDlg 0x20383738 hWnd=???}

Hope things are clear

-- modified at 11:22 Tuesday 18th October, 2005

Re: Access Violation Error

Rage18-Oct-05 5:43

Rage

18-Oct-05 5:43

nripun wrote:
the Debug Assertion Error i mentioned

Which line of code is actually asserting ? Can you post the code (meaning the block containing the ASSERT(), not your line of code) ?

nripun wrote:
..... it actually worked

Here I have to second DAvid : It seems to have worked, most surely this will not survive the release version.

You need to do all this at least inside OnInitDialog, or after it has been called, otherwise the controls do not exist as such (which explains the hWnd = ??) you mentioned.

~RaGE();

Re: Access Violation Error

nripun19-Oct-05 0:45

nripun

19-Oct-05 0:45

Sorry guys, My Mistake. Big Grin | :-D

Before the line ,
pListBox = (CListBox*) this->GetDlgItem(IDC_LISTBOX1);
there was a sprintf() function which was not successful D'Oh! | :doh:

.
I corrected the sprintf() and now the code works fine. The mistake in the sprintf() caused the hWnd=???

Thank you all..

Re: Access Violation Error

Rage18-Oct-05 5:47

Rage

18-Oct-05 5:47

OK, afxwin2.inl, line 590

_AFXWIN_INLINE void CButton::SetCheck(int nCheck)
	{ ASSERT(::IsWindow(m_hWnd)); ::SendMessage(m_hWnd, BM_SETCHECK, nCheck, 0); }

meaning your control has not been initialized yet. You are calling this function too early (the handle m_hWnd has not been assigned yet).

~RaGE();

Re: Access Violation Error

David Crow18-Oct-05 5:50

David Crow

18-Oct-05 5:50

nripun wrote:
Debug Assertion Error
File:afxwin2.inl
Line 590

Which indicates that the (control) window does not yet exist.

What does the dialog's DoDataExchange() and BEGIN_MESSAGE_MAP() methods look like?

"Take only what you need and leave the land as you found it." - Native American Proverb

time help pleas

Gapilazo18-Oct-05 3:18

Gapilazo

18-Oct-05 3:18

How can i change time on my computer with c++ ofcorse

Re: time help pleas

Calc2018-Oct-05 3:44

Calc20

18-Oct-05 3:44

There is function in Windows API called SetSystemTime(). You can find an example in MSDN.

Re: time help pleas

vikas amin18-Oct-05 3:45

vikas amin

18-Oct-05 3:45

Use the function
---SetSystemTime()----
Just search the MSDN u get the details
Cool | :cool:

Vikas Amin
Embin Technology
Bombay
vikas.amin@embin.com

Re: time help pleas

David Crow18-Oct-05 3:50

David Crow

18-Oct-05 3:50

How about SetLocalTime()?

"Take only what you need and leave the land as you found it." - Native American Proverb

CString memory leak

mails_aphale18-Oct-05 2:50

mails_aphale

18-Oct-05 2:50

I have used many CString variables in functions.
code works fine but at the end, in CString destructor it gives null pointer exception.

in destructor, in FreeData() call, delete operator gives exception.

is there something that I left out
can somebody help me out ?
thanx in advance.

Re: CString memory leak

prasad_som18-Oct-05 3:02

prasad_som

18-Oct-05 3:02

post the code

Re: CString memory leak

mails_aphale18-Oct-05 3:48

mails_aphale

18-Oct-05 3:48

code is big & it contains lot of my function calls (user defined). it seems difficult.

Re: CString memory leak

vikas amin18-Oct-05 3:51