C / C++ / MFC

disable individual rows of a listctrl

11-Nov-02 14:13

Hyello,

I have a Wizard in my application which works flawlessly on Windows 2000/Xp, but under Windows 98, I get some weird stuff going on. On some pages, when you hit the Next button, it advances either back to the beginning, or some other page other than the next one --- though it does work sometimes.

Has any run into this problem? I've been trying to trace the problem through in Windows 98, but the whole os tends to lock up and it's really frustrating! WTF | :WTF:

Thanks!

swine

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fordge11-Nov-02 13:55

fordge

11-Nov-02 13:55

can anyone tell me how i can disable selection of individual rows of a listctrl.
if u suggest ODS_DISABLED
please elaborate
cause i cant get it to work properly..

Swinefeaster11-Nov-02 14:08

11-Nov-02 14:08

i believe you have to implement this yourself Frown | :(

swine

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fordge11-Nov-02 20:37

fordge

11-Nov-02 20:37

do u remember the vstudio 6 help
the msdn then had the index and u could filter the list box accoring to language like for vc vb ...etc..and according to the filter all the contents not in that language would be disabled(grayed out)..
thats the kind of thing im talking off..

do umean to say that that not possible standardly and has to be implemented seperately??

Swinefeaster11-Nov-02 20:40

11-Nov-02 20:40

yep, as far as i know. it's not that hard to do though... there's a bunch of articles on how to do stuff like this here in codeproject. you could also do a search for CListCtrl::DrawItem().

cheers,

swine

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Michael Dunn11-Nov-02 16:55

Michael Dunn

11-Nov-02 16:55

Handle LVN_ITEMCHANGING. Examine the iItem and uNewState members of the struct you are passed, and if an item is becoming selected, and you don't want it to be, return TRUE from the handler to prevent the change.

--Mike--
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Anonymous11-Nov-02 20:38

CLabel control with property sheet question

11-Nov-02 20:38

please elaborate if possible
a code snipet would be helpful

Cannot figure it out

ed987111-Nov-02 13:01

ed9871

11-Nov-02 13:01

I have never gotten an error in release mode that I did not get in debug mode. In CView::OnFilePrint() somewhere between OnBeginPrinting and OnPrepareDC (the two functions I can override and put some message boxes in so I can see where I am while in release mode) I am getting this:

Unhandled exception at 0x0050f277 in Paradigm.exe: 0xC0000005: Access violation reading location 0x00000002.

I have exhausted my knowledge trying to figure out why this is happening.

I can set a breakpoint for this address and it hits it three other times during execution before it bombs in OnFilePrint(). VS says there is no source code associated with this address. The dissassembly is as follows:

0050F277 66 81 7B 02 FF FF cmp word ptr [ebx+2],0FFFFh

Where do I go from here? I'm sure there are things to do that are outside my knowledge base. It works perfectly in debug mode.

Ed

Re: Cannot figure it out

Christian Graus11-Nov-02 17:19

Christian Graus

11-Nov-02 17:19

There is a good article here on CP about how to fool the debug version into thinking it's a release version, so you can catch these errors in the debugger.

Christian

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DalTXColtsFan11-Nov-02 12:53

DalTXColtsFan

11-Nov-02 12:53

Greetings all,

I have a question. I'm using Norm Almond's CLabel control on a Property Page. I want to allow the user to select some colors and then have a rectangle on the dialog with the color the user chose. It was working perfectly as a CDialog.

What's happening now is I'm trying to make that dialog a PropertyPage as part of a PropertySheet. Here are the changes I made to InitInstance:

BOOL CPropertySheetDemoApp::InitInstance()
{
// Standard initialization
// If you are not using these features and wish to reduce the size
// of your final executable, you should remove from the following
// the specific initialization routines you do not need.

/*CPropertySheetDemoDlg dlg;
m_pMainWnd = &dlg;
int nResponse = dlg.DoModal();
if (nResponse == IDOK)
{
// TODO: Place code here to handle when the dialog is
// dismissed with OK
}
else if (nResponse == IDCANCEL)
{
// TODO: Place code here to handle when the dialog is
// dismissed with Cancel
}*/

CPropertySheet mySheet;
CMyPropertyPage myDemoPage;
myDemoPage.m_lblTest.SetBkColor(RGB(1.0, 1.0, 1.0));
mySheet.AddPage(&myDemoPage);

mySheet.DoModal();

// Since the dialog has been closed, return FALSE so that we exit the
// application, rather than start the application's message pump.
return FALSE;
}

As you can see I just commented out the stuff to bring up the initial dialog and am trying to bring up the property sheet instead. The error I'm getting is a debug assertion failure in the UpdateSurface() method of the CLabel class. It seems to be complaining that the window hasn't been drawn or doesn't have an hWnd yet.

Any suggestions? I just want to be able to initialize the colors on the labels as they come up, and they may not always be the same colors.

I'd appreciate any suggestions!

Joe

CSocket::Receive (from more than one computer)

Walote11-Nov-02 10:47

Walote

11-Nov-02 10:47

Hi!!

I have a connection between two computers, that work's OK. Command NETSTAT show the ESTABLISHED status under this connection, but I need to receive from a third computer. On the 3rd computer, the NETSTAT command show the ESTABLISHED status too, but the CSocket::Receive from the server, can not listen from there...

what was wrong?

Thank's.... Walote

CString from a UI Thread

Anonymous11-Nov-02 10:25

11-Nov-02 10:25

Hello,
I have a UI thread and I do a PostMessage from the thread to the application with the lParam set as a CString.. in my receiving function i do a

LRESULT CMainFrame::OnMarkOffLine(WPARAM wParam, LPARAM lParam)
{
	CString* name = (CString*)lParam;
	CString strName = *name;
..SNIP........

but i am getting a access violation here...

CString::CString(const CString& stringSrc)
{
	ASSERT(stringSrc.GetData()->nRefs != 0); <-Here
	if (stringSrc.GetData()->nRefs >= 0)
	{
		ASSERT(stringSrc.GetData() != _afxDataNil);
		m_pchData = stringSrc.m_pchData;
		InterlockedIncrement(&GetData()->nRefs);
	}
	else
	{
		Init();
		*this = stringSrc.m_pchData;
	}
}

What am I doing wrong??

dabs11-Nov-02 10:39

dabs

11-Nov-02 10:39

There is nothing inherently wrong with the code you posted (although I would recommend that you replace the C-style typecast with a more appropriate C++ typecast but that's another matter altogether). Show us the code that sends (or posts) this message.

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Anonymous11-Nov-02 10:45

This seemed to fix it.. weird

11-Nov-02 10:45

Here's the PostMessage

PostMessage(this->GetMainWnd()->GetSafeHwnd(),UWM_OFFLINE,0,(LPARAM)&m_strDns);

Anonymous11-Nov-02 10:59

11-Nov-02 10:59

CString name = (LPCSTR)lParam;

instead of the

CString* name = (CString*)lParam

Re: Its not fixed

Anonymous11-Nov-02 11:26

11-Nov-02 11:26

Actually the error went away but the string contains garbage..

Dead | X|

Swinefeaster11-Nov-02 14:07

11-Nov-02 14:07

I know exactly what your problem is! Smile | :)

You can't use pointers to objects with a PostMessage(), because PostMessage() does not hang the calling thread and wait until the receiving thread processes the message, unlike SendMessage(). What happens is that the CString object in your calling thread gets destroyed before the receiving thread gets a chance to access the strings contents.

The solution to this is kind of a pain. You need to create a central map / list container that holds a bunch of strings, and then pass handles (or even pointers) to those strings in your messages. Then you delete the string once you receive the message, or perhaps after some time.

Hope this helps!

swine

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peterchen11-Nov-02 14:18

peterchen

11-Nov-02 14:18

When using PostMessage with non-primitive data types, alwaysuse a deep copy of the object - passing a reference to an object that might cease to exist before the message is handled is just asking for trouble:

CString * lp = new CString(m_strDns);
if (!PostMessage(...,...,..., (LPARAM) lp)) // message queue full, message not send:
  delete lp;

the error handler avoids a memory leak (although you might be tempted to retry posting the message if your handling would break down otherwise)

the message handler needs to delete the object again:

CString* name = (CString*)lParam;
_ASSERTE(name!=NULL)
CString strName = *name;
delete name;

This solution is IMO easier than the one suggested in the post above..

*) reason:

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Anonymous11-Nov-02 14:56

11-Nov-02 14:56

Thanks to both of you for your posts.. I had a feeling that the thread was exiting before the string could be accessed by my main app.. I went with the easier solution posted below..

Thanks again,
Rob

Swinefeaster13-Nov-02 13:28