UpdateData confusion - C / C++ / MFC Discussion Boards

John M. Drescher10-Jun-02 20:59

10-Jun-02 20:59

I use method 2 very much in my applications and it works good. However as pointed out MFC declares its maps in a per thread basis so if you create a view \ CWnd in a different thread than the main application thread you will probably run into many problems especially with removing the view. This problem almost made me move over to WTL / ATL but I was able to modify my application so that all views were created by the main thread.

John

Re: Worker Thread and Main Window

Alexandru Savescu10-Jun-02 7:15

Alexandru Savescu

10-Jun-02 7:15

arthivjii wrote:
From the worked thread I want to access the "Document" class of the MDI Application.

You should never do that! Never touch the GUI object from a different thread! If you step into the code you will see it crashes in the AssertValid function. Here are the comments from the MFC sources:

// Note: if either of the above asserts fire and you are
// writing a multithreaded application, it is likely that
// you have passed a C++ object from one thread to another
// and have used that object in a way that was not intended.
// (only simple inline wrapper functions should be used)
//
// In general, CWnd objects should be passed by HWND from
// one thread to another.  The receiving thread can wrap
// the HWND with a CWnd object by using CWnd::FromHandle.
//
// It is dangerous to pass C++ objects from one thread to
// another, unless the objects are designed to be used in
// such a manner.

You should post a message to the main window instead. For better understanding of the worker threads read Using worker threads

Best regards,
Alexandru Savescu

Re: Worker Thread and Main Window

arthivjii10-Jun-02 7:30

arthivjii

10-Jun-02 7:30

Hi,
Thanks a lot for the suggestions. I have now understood the mistakes which I was doing.

Thanks
Arthi Smile | :)

Re: Worker Thread and Main Window

Neville Franks10-Jun-02 10:04

Neville Franks

10-Jun-02 10:04

Alexpro wrote:
You should never do that! Never touch the GUI object from a different thread!

I can't agree with you here. There are lots of pitfalls doing GUI stuff from a Worker Thread but it is mostly all doable. The main problem is that MFC's handle map's are maintained on a per thread basis, so your worker thread can't access the CWnd from another thread. It still can use the hWnd to do GUI stuff and also under some circumstances use CWnd's.

I have a simple class I've written which attachs a CWnd* to the current worker threads message map. It is similar to CWnd::Attach() and resolves the MFC problems with ASSERT_VALID( this ). I make use of these techniques in ED for Windows (see sig), which uses threads extensively. If anyone wants a copy let me know.

Neville Franks, Author of ED for Windows. www.getsoft.com

arguments

Nnamdi Onyeyiri10-Jun-02 6:36

Nnamdi Onyeyiri

10-Jun-02 6:36

How (if possible) can you make a dialog app that can take command line parameters like a console app?

==================================================
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Re: arguments

C^hris L^osinger10-Jun-02 6:53

C^hris L^osinger

10-Jun-02 6:53

simple: just use _argc and _argv in your CWinApp's InitInstance, before the DoModal call that starts the dialog. use them just as you would use argv and argc in a command line app.

-c

Cheap oil. It's worth it!

ISEffects - effects for images

Reading Certificates from IE store

User 988510-Jun-02 6:41

User 9885

10-Jun-02 6:41

Do anyone know how to do this?

I tried CertOpenSystemStore with name "Other People", but could not get the certificate. It created another store with the same name. Now when I enumerate stores, I get two "Other People" stores.

Thomas George

modified 29-Aug-18 21:01pm.

UpdateData confusion

dazinith10-Jun-02 5:23

dazinith

10-Jun-02 5:23

ok.. part of my data validation on a dialog of mine checks to make sure a field isn't blank, if so the datavalidation fails and gives an error.. so heres my problem..

i have a button in the dialog which pops up another dialog and lets then choose a city in a state, when they hit ok it fills out some fields in the main dialog with the values from the citystate dialog.. like this..

UpdateData(true); // store values into variables
CCityStateDlg dlg;
if (dlg.DoModal() == IDOK)
{
m_strCity = dlg.m_strCity;
m_strState = dlg.m_strState;
UpdateData(false); // put variables into CEdit fields
}

my problem is that when UpdateData(true); gets called in the begining it causes my errors for blank fields to get called.. but if i don't call it then when i call UpdateData(false); it clears out the other fields in the dialog because the values in the fields were never put in the variables..

so is it ok to do this?

CCityStateDlg dlg;
if (dlg.DoModal() == IDOK)
{
CEdit* pCity = (CEdit*)GetDlgItem(IDC_CITY);
CEdit* pState = (CEdit*)GetDlgItem(IDC_STATE);
pCity->SetWindowText(dlg.m_strCity);
pCState->SetWindowText(dlg.m_strState);
}

and if so does that mean that UpdateData is pointless, or is it just not possible to use in this situation? Basicly i don't want to give the user the errors about blank fields when they click the button because they may fill out these other fields after they choose the city/state..

thanks for the help!

-dz

Re: UpdateData confusion

Joaquín M López Muñoz10-Jun-02 5:36

Joaquín M López Muñoz

10-Jun-02 5:36

I'd say your proposed solution is fine, given the constraints of your design. Ideally, you only call UpdateData(FALSE) when pressing the "Accept" button --during the lifetime of the dialog the data are supposed to inhabit the controls, and only at exit time are they transfered to the appropriate member variables.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: UpdateData confusion

Ed Gadziemski10-Jun-02 11:32

Ed Gadziemski

10-Jun-02 11:32

This is a little off-topic from your question and is a design issue instead, but why don't you use dropdown listboxes for city and state? Then you wouldn't have to deal with a second dialog.

Re: UpdateData confusion

dazinith11-Jun-02 3:16

dazinith

11-Jun-02 3:16

Welp, i use the dialog in multiple places, and i haven't taken the time to figure out how to place a propertypage into a static frame inside of a dialog.. basicly i need to reuse this state/city picker in a few different dialogs for different reasons.. but it would be nice if it was just listed there.. maybe in a future version Smile | :)

-dz

Re: UpdateData confusion

dazinith11-Jun-02 3:17

dazinith

11-Jun-02 3:17

Welp, i use the dialog in multiple places, and i haven't taken the time to figure out how to place a propertypage into a static frame inside of a dialog (although ive seen it done in SPAPrefs on CP).. basicly i need to reuse this state/city picker (which does use dropdown listboxes) in a few different dialogs for different reasons.. but it would be nice if it was just listed there.. maybe in a future version Smile | :)

-dz

Re: UpdateData confusion

John M. Drescher10-Jun-02 21:13

John M. Drescher

10-Jun-02 21:13

dazinith wrote:
so is it ok to do this?
Yes it is ok to do that.

dazinith wrote:
and if so does that mean that UpdateData is pointless, or is it just not possible to use in this situation?

No you could have set a boolean and checked it in your DoDataExchange and used its value to bypass the data validation routines. UpdateData is not pointless it saves you from having to get, set and validate the dialog data yourself. I usually have several conditionals and some GetWindowText() and SetWindowText() in the DoDataExchange() and call UpdateData(TRUE) and UpdateData(FALSE) several times in my complex dialogs.

John

watch window in debug doesn't work

John Oliver10-Jun-02 5:12

John Oliver

10-Jun-02 5:12

Hello, I'm using VC++v6.

When I'm debugging, I cannot view any variable values in the watch window when I step through e.g.

NAME m_PathName
VALUE CXX0017:Error: symbol "m_PathName" not found

The variable is in scope and initialised, and i'm definately in debug mode. My variables window is also empty. I have used them successfully before but I can't figure out why not now.

Can anybody help, thanks,
John

Re: watch window in debug doesn't work

Joaquín M López Muñoz10-Jun-02 5:32

Joaquín M López Muñoz

10-Jun-02 5:32

Make sure you have the "Debug info" option switched on. If that doesn't work, exit VC++, delete all .ncb, .opt, .plg, .pch and .pdb files in your project and try again.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

How to Dynamically add an Item to Menu?

10-Jun-02 4:44

Hi,

I was wondering how could I dynamically add an item to a menu (or how to add a menu dynamically).
I appreciate your help.
Thanks.

Re: How to Dynamically add an Item to Menu?

Lanny Thompson10-Jun-02 4:59

Lanny Thompson

10-Jun-02 4:59

Hi,
I believe the MSDN library discs have a sample called DYNAMENU that shows how to dynamically add items to a menu.

Hope that helps,
Lan

Re: How to Dynamically add an Item to Menu?

Alexandru Savescu10-Jun-02 5:04

Alexandru Savescu

10-Jun-02 5:04

Use CMenu::InsertMenu

Best regards,
Alexandru Savescu

Re: How to Dynamically add an Item to Menu?

redeemer10-Jun-02 5:31

redeemer

10-Jun-02 5:31

Use InsertMenu()

BOOL InsertMenu(
HMENU hMenu, // handle to menu
UINT uPosition, // item that new item precedes
UINT uFlags, // options
UINT_PTR uIDNewItem, // identifier, menu, or submenu
LPCTSTR lpNewItem // menu item content
);

10-Jun-02 4:34

How can I send EMails from an MFC Project without MAPI functionality and without Doc/View Architecture???
Please send me some source Code!!!!! Cry | :((

Re: EMail

Mazdak10-Jun-02 4:46

Mazdak

10-Jun-02 4:46

Check this article:

CCmc v1.0 - A CMC Implementation

Mazy

"The more I search, the more my need
For you,
The more I bless, the more I bleed
For you."The Outlaw Torn-Metallica

Re: EMail

Ed Gadziemski10-Jun-02 11:41

Ed Gadziemski

10-Jun-02 11:41

Why, Mazy, you disobeyed the order to Send Source Code!!!! If he'd wanted a link, he would've asked you to Post Article Link!!! Smile | :)

Re: EMail

Mazdak10-Jun-02 18:51

Mazdak

10-Jun-02 18:51

Ed Gadziemski wrote:
Why, Mazy, you disobeyed the order to Send Source Code!!!! If he'd wanted a link, he would've asked you to Post Article Link!!!

Hey this is very common way in answering questions. Many times people don't ask foe link but after that when somebody give them some link they become glad for it.So why should I disobey. Frown | :(

Re: EMail

Ed Gadziemski11-Jun-02 2:03

Ed Gadziemski

11-Jun-02 2:03

That was a joke. You see, the person who wrote "Send Source Code!!!!" was making demands on CP members as if he were King or President. Similar to "You must do this. I command you." So, the joke was that you did not give him what he commanded. Sorry if I was not clear. Rose | [Rose]

How to capture the message of a subcontrol which was created dynamicly?

white jungle10-Jun-02 4:38

white jungle

10-Jun-02 4:38

I create a ListBox in a Dialog dynamically!I want to capture
the message LBN_SELCHANGE of the control ListBox,I create it like this:
m_ListBox.Create (WS_CHILD|WS_VISIBLE,rc,this,IDC_LIST_BOX);//CListBox m_ListBox
And I use the following code to check if the dialog capture
the message:
LRESULT CMyDlg::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
{
if(message==LBN_SELCHANGE)
{
AfxMessageBox ("LBN_SELCHANGE");
}
return CDialog::WindowProc(message, wParam, lParam);
}

But to my surprise,I found that it can capture the mesage only once,it occured at the begin of the program.after that ,it can't be captured.
How can solve the problem!
Thank you!

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