MFC problem, nobody encounter this before!?

I need to pop up a messagebox in OnSelchangeCombo1 but the following code will cause MFC to hang! if your combo box is having a scrollbar and you right click on the scrollbar. :mad: :mad: :mad:

void CDialogTestDlg::OnSelchangeCombo1()
{
// TODO: Add your control notification handler code here

AfxMessageBox("Hello");
}



How to get around this stupid problem??

[ merged ]

:wave: :wave:

Hello!?

Any help ??

Or just tell me how to diable the right click on a scroll bar?

Thanks a lot for the reply. :D

:wave:
But., It seems there are still some misundertsandings here.

As i mentioned earlier (may be i am not clear), you see., When user drop down my combo box with scroll bar there, and as he is making a selection by clicking on one specific of the item, i pop up a warning message if he really want the selection. If he is ok (meaning he click on the "OK" button on the modal dlg) the selection is made and everything went smoothly. All this is done in the OnSelchangeCombo1 function.

No issue here., everything is purrfect. I pop up message box/modal box where i want it to, give the user appropriate warning if he want to continue and return normally.

Now, the problem. if the user drop down the combo box and do a RIGHT CLICK, yes it is "RIGHT CLICK", on the scroll bar beside any item in the combo box, this is equivalent to left click of the mouse for the item. The OnSelchangeCombo1 will thus get called. But this time, the dialog box get screwed up. I noticed that the problem could be due to the program is trying to display the context menu and modal dialog box at the same time??
You probably have noticed that, when you right click on a scroll bar, a context menu is pop up by default whenever there is a scroll bar.

So if i can pop up message smoothly if i left click on the combo box, why i can't pop up message if i do a right click?? In other words, it is perfectly legal for me to do some sanity check by poping up a modal box inside the function OnSelchangeCombo1 ( where CBN_SELCHANGE message is processed) before i proceed to anything., and of course this works. Since this works, there is no reason why the right click on scroll bar should failed because of the modal dlg box.

I hope you understand my point .. :D :D

... When user drop down my combo box with scroll bar there, and as he is making a selection by clicking on one specific of the item, i pop up a warning message if he really want the selection. If he is ok (meaning he click on the "OK" button on the modal dlg) the selection is made and everything went smoothly. All this is done in the OnSelchangeCombo1 function.
I think that Paul McKenzie was trying to give you the generally-accepted advice that you should do very little inside the notifications from a control. These notifications are not meant to allow extensive processing, or anything that might take more than a moment or two, or otherwise interfere with the message pump of the application. So, putting a MessageBox inside the notification is not a great idea.

If you need to perform extensive processing after the user has selected a new item, then post a user-defined message to yourself (using PostMessage) so that the message shows up at the end of the message queue. Perform the extensive processing inside the handler for the user-defined message.

As a further thought, maybe your problems are caused by the WM_CONTEXTMENU handler. Post the code from that handler too.

Mike

Well, why are you trying to display the context menu and modal dialog box at the same time? :confused:
None of the comboboxes in my applications shows me the context menu when I do a "RIGHT CLICK" on the combobox scollbar!

Hi,

The context menu is not displayed by me. I don't even know how to remove this context menu which is put there by default by MFC framework whenever there is a scroll bar. If your combo scroll bar doesn't show context menu at all without you doing anything, then i am pretty surprised.. i am using VC++ 6.0.

I will create a project and attached here in a while. Thanks for all the info.. :D :D

When posting a project, eliminate the unnecessary files such as *.aps, *.opt, *ncb, etc. The only files needed are the *.dsp, *.dsw, resource files, and source code.

Regards,

Paul McKenzie

hi mce ,
i run your project but when i right click on the scroll bar nothing happens.
i mean it does not hang. but simply do not respond. as right click on scrolll bar has not been handled. i am not sure.if this could be done by some Hooking of the commmon Controls events.

put straight.
this certainly does not hang. it just does not respond.

regards
Dingo

Ok, thanks for all the replies.

At lease i can confirm that this is part of the problem in MFC or at least something related to it.

And i am very convinced that some guys who provided the framework realized this issue and fix it in VC++ 7.0.

And to all the recommendations that i should not pop up message box in the handling of the OnSelchangeCombo1, i think really, this is something that need to be fixed by microsoft rather than asking the programmer not to do so in the message handling. After all, it is already allowed through left clicking, so why right clicking is not handled properly? This sounds more like a bug in the Microsoft. :D :D

And back to my original problem, if i were to remove all the message box in the OnSelchangeCombo1, i don't think my software tester and my boss will agree with me. Why? This is what they are telling me :-

The user make a selection in the combo box, and it pass through. Why the user is only informed/warned about the particular selection much later on?? rather than the moment the selection is made? If you were me, what would you say ? i need a valid reason to fight them off :D :D unless i tell them this is a bug in the Microsoft and i can't do anything better.

Here is a very simple MFC project.
...
Just drop down the combobox and make a selection. Purrfect.

Then drop down again the combo box and try to right click on the scroll bar.. BOOM......... :D :D Ok, I've just tested your sanple on my Win XP SP2 PC with VC++6.0 SP6.
The result is the same as with comboboxes in all my applications.
There is no context menu at all! :cool:

As you may notice in the code, i can;'t see why i shouldn't pop up a dlg box inside the OnSelchangeCombo1? Or really there is a better way here to do what i want to achieve? Appreciate all feedback..................Note, that you are asking the user about "Do you really want to change selection" after this selection has been already changed! You cannot prevent this any way except by re-selecting the previously selected item.
In this case you have to save this information after the user chooses "Yes".

That is funny. I am using XP sp2, vc++ i think is sp6 too (though I am not sure how to verify the sp version of my vc++ 6).
You can see this information in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\6.0\ServicePacks key

My environment was VC6, SP5, WinXP Pro, and definitely exhibited the problem reported by mce.

But again, the problem is your own making:
And to all the recommendations that i should not pop up message box in the handling of the OnSelchangeCombo1, ... , it is already allowed through left clicking, so why right clicking is not handled properly? This sounds more like a bug in the Microsoft
It's not allowed through left clicking either. Don't pop up a message box in any of the notifications from a child control, or otherwise perform extensive processing, or anything that might take more than a moment or two, or otherwise interfere with the message pump of the application. So, putting a MessageBox inside the notification is not a great idea, whether a left click or a right click.

As Paul McKenzie stated, you have focused on a false solution, which doesn't work in your environment (at least), so why stick with it when better options exist. Post a message to yourself, as previously advised. The following works fine for me:
// in dialogTestDlg.h : header file

#define CM_SPECIAL_MESSAGE (WM_APP+1)

// ...

public:
LRESULT OnSpecialMessage(LPARAM lParam, WPARAM wParam);

// in dialogTestDlg.cpp : implementation file

// ...
BEGIN_MESSAGE_MAP(CDialogTestDlg, CDialog)
//{{AFX_MSG_MAP(CDialogTestDlg)
ON_WM_SYSCOMMAND()
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
ON_CBN_SELCHANGE(IDC_COMBO1, OnSelchangeCombo1)
ON_CBN_DROPDOWN(IDC_COMBO1, OnDropdownCombo1)
ON_MESSAGE(CM_SPECIAL_MESSAGE, OnSpecialMessage)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

// ...

void CDialogTestDlg::OnSelchangeCombo1()
{
// TODO: Add your control notification handler code here
int sel = m_CtrlCombo.GetCurSel();

if(sel != -1){

// save data about old and new selection into member variables, so that
// it can be used in the OnSpecialMessage handler

// naturally, wParam and lParam do not need to be zero. You can use special values for
//wparam and lparam to encode special meanings to the message

PostMessage(CM_SPECIAL_MESSAGE, 0L, 0L );

}

}

LRESULT CDialogTestDlg::OnSpecialMessage(LPARAM lParam, WPARAM wParam)
{
// posted to myself just after the user changes the selection in the combo box

int nRet = MessageBox(_T("Do you really want to change selection?"),"Warning",MB_YESNO);

if(nRet == IDYES){

//Set some value here

}

else{


//just restore the previous selection
}
return 0L;

}
Mike

SP6 for VS6 is free for download, BTW! No upgrade is needed. ;)

Run your app. Open the combobox and drop down the list. Use the down arrow on your keyboard to scroll down the list to the selection you want. Your messagebox will pop up on every item in the list. That's why it's a bad idea.Good point. If the user uses the keyboard to control the combo box, they will see that the program is being totally user-unfriendly and a hindrance to getting any work done.

To mce:

Does your boss and tester ever run their programs using the keyboard instead of the mouse? If not, let them try their idea using only a keyboard -- maybe that will finally convince them to drop this silly idea of popping up message boxes.

Regards,

Paul McKenzie

Agree with your opinion.

mce: I think it's better to use tooltip instead of message box

I don't see how that helps in this instance either.

Interesting!
I get context menu by right mouse click on the ListBox scrollbar, but not on the listbox part of the combobox!
Other version of common controls? :confused:
I am using IE 7.
What IE version are you using?

Interesting!
I get context menu by right mouse click on the ListBox scrollbar, but not on the listbox part of the combobox!
Other version of common controls? :confused:
I am using IE 7.
What IE version are you using?

I am using IE 6. But, i don think it is related to IE version. I have tried to run the application on Windows Vista with IE 7, and it display the same behavior.