Callback functions - C / C++ / MFC Discussion Boards

Re: nope

7-Aug-01 21:03

lol i just figured that out Smile | :)

thx anyways
Big Grin | :-D

Re: weird, i dun get if()?

Dean Goodman8-Aug-01 6:24

Dean Goodman

8-Aug-01 6:24

Also, you never initialize v to be 0 -- probably explains why v is always 75536.

Re: weird, i dun get if()?

17-Aug-01 10:48

Try initializing v to 0.

Programming the control panel

7-Aug-01 20:23

Can someone give me some tips on programming the systems control panels in code. Specifically the display control panel.

Thanks.

Re: LOGON32_LOGON_UNLOCK

8-Aug-01 0:45

use the platform SDK version

How do I show a short description of an item in a combo list?

7-Aug-01 12:28

I'm creating a program from which the user pick an item from a dropdown combo box then depend on what it is, display a short description in a text edit field, how can this be done? I'm pretty familar with the variables and classes and stuff, just need a way to do this... Please help.

Re: How do I show a short description of an item in a combo list?

Carlos Antollini7-Aug-01 16:09

Carlos Antollini

7-Aug-01 16:09

You need to use the CCombobox::GetItemData() method.
But you first need to add the strings in the ComboBox and Set the Itemdata of each string. For this you have the CComboBox::SetItemData.
When the user pick in the combox you can get the ItemData and with this value you can search for a associated string with that value.

Good Luck!!!!
Beer | [beer]

Carlos Antollini.

Callback functions

Jake Palmer7-Aug-01 11:52

Jake Palmer

7-Aug-01 11:52

I'm trying to use the function AVISave, which takes as a parameter a callback function:
AVISAVECALLBACK lpfnCallback
with the prototype:
LONG PASCAL SaveCallback(int nPercent)

When it comes to passing a function to another function, we leave the realm of any C++ that I understand. How do I call AVISave? And, where does the "Pascal" come from?
thanks,
Jake

Re: Callback functions

Andrew Peace7-Aug-01 13:03

Andrew Peace

7-Aug-01 13:03

I don't know the prototype for AVISave, but this is the general idea:

LONG PASCAL SaveCallback(int nPercent)
{
   UpdateProgress(nPercent);
}

void SaveAVIFile()
{
   AVISave(SaveCallback, /*the othe parameters here*/);
}

So really, in essence, you just treat the function as a variable.

Hope that helps,
> Andrew.

Re: Callback functions - Still not working

Jake Palmer8-Aug-01 7:19

Jake Palmer

8-Aug-01 7:19

This is what my code looks like, where AVISave takes a callback function as 3rd arg:
long PASCAL CBadClass::SaveCallback(int percent)
{
return AVIERR_OK;
}
...
bool CBadClass::Foo()
{
AVISave(...,SaveCallback, ...);
}
This gives me the compilation error:
error C2664: 'AVISaveA' : cannot convert parameter 3 from
'long (int)' to 'int (__stdcall *)(int)'
None of the functions with this name in scope match the target type

needless to say, I've got no ideas here Dead | X|

thanks,
Jake

Re: Callback functions - Still not working

Michael Dunn8-Aug-01 7:39

Michael Dunn

8-Aug-01 7:39

Your question is answered in the VC forum FAQ. See http://www.codeproject.com/useritems/cppforumfaq.asp#cpp_callbacks

--Mike--
http://home.inreach.com/mdunn/
"Make sure that if you are using a blow torch that you don't set anything on fire."
-- Chris Maunder

Re: Callback functions - STILL not working

Jake Palmer8-Aug-01 12:24

Jake Palmer

8-Aug-01 12:24

The ForumFAQ article has tons of good stuff, including telling me to make my callback function global or static, however I've tried it with each and still get the exact same error as before (see previous message). Dead | X|

So, something else is killing me, I guess...any more ideas?
thanks,
Jake

Re: Callback functions - STILL not working

Michael Dunn9-Aug-01 0:54

Michael Dunn

9-Aug-01 0:54

Your member function doesn't have the required prototype. It's

long PASCAL CBadClass::SaveCallback(int percent)

but AVISAVECALLBACK is defined as

typedef BOOL (FAR PASCAL * AVISAVECALLBACK)(int);

Change the return type of your function to BOOL. And BTW, FAR is obsolete and can be ignored, and PASCAL has been replaced by CALLBACK in Win32.

--Mike--
http://home.inreach.com/mdunn/
"Make sure that if you are using a blow torch that you don't set anything on fire."
-- Chris Maunder

Re: Callback functions - Still not working

Christian Graus8-Aug-01 12:40

Christian Graus

8-Aug-01 12:40

Well, for starters the parameter is a pointer to the callback function, so you might try &SaveCallback.

Christian

Secrets of a happy marriage #27:

Never go to bed if you are mad at each other. It's more fun to stay up and fight.

Exception handling

Frank Deo7-Aug-01 11:47

Frank Deo

7-Aug-01 11:47

Hello,

In my app, I've got a function that performes a calculation on a string entered by the user in an editbox. If the text formatting (encrypted data) isnt correct the function fails with an unhandled exception error.

I've tried try{} and catch{}, but they don't seem to "Catch" the error. How can I trap the error (or any exception for that matter) so that I can handle this error gracefully. Wink | ;)

Is there any way to find out exactly what type of CException (CFileException, etc) is being thrown?

Thanks,
Frank

Re: Exception handling

Andrew Peace7-Aug-01 11:54

Andrew Peace

7-Aug-01 11:54

It sounds to me either one of two things:

1. You haven't put your code in a try block:

try 
{
   // put your code here
}
catch (CMyException &e) 
{
   // put your error handler here
}

2. You're catching a different type than you threw. The best thing to do is to throw by value, catch by reference, as show below:

void MyFunc()
{
   throw CMyException();
}

void main()
{
   try
   {
      MyFunc();
   }
   catch (CMyExcetpion &e)
   {
      cout << "Error!";
   }
}

Alternatively, you could use catch (...) which catches all exceptions.

> Andrew.

Re: Exception handling

Frank Deo7-Aug-01 12:01

Frank Deo

7-Aug-01 12:01

Thanks Andrew...

I'll give catch(...) a try.

Frank

Using ATL objects in the project its created

Cem Kalyoncu7-Aug-01 11:36

Cem Kalyoncu

7-Aug-01 11:36

I have a big project that has 5 ATL simple object. The first one is called as Header. This Header module will contain a collection of other objects. But cannot create these objects in the same application(though I can create them in another VB application). Can you help me?
Thanks a lot,
Cem

CView and CFormView

Matt Newman7-Aug-01 11:17

Matt Newman

7-Aug-01 11:17

I have an MDI application using CView. I have a dialog that is setup as a CFormView. How can i show the CFormView as a child on command?

-Matt Newman Suspicious | :suss:

Re: CView and CFormView

Christian Graus8-Aug-01 12:41

Christian Graus

8-Aug-01 12:41

Why can't you just set it up as a dialog box ?

Christian

Secrets of a happy marriage #27:

Never go to bed if you are mad at each other. It's more fun to stay up and fight.

Re: CView and CFormView

Matt Newman8-Aug-01 17:43

Matt Newman

8-Aug-01 17:43

>Why can't you just set it up as a dialog box ?
Because this way the user can make it lose focus while the are working but don't have to close it.

-Matt Newman Suspicious | :suss:

Removing close button from wizard

7-Aug-01 10:51

Hi,

I use CPropertyPageEx to create Wizard, is there a way
to remove the close button on the upper right corner? thanks.

p.c.

Re: Removing close button from wizard

Frank Deo7-Aug-01 11:22

Frank Deo

7-Aug-01 11:22

Handle OnInitDialog in your CPropertySheetEx class.

This is how I've removed the maximize button (Or disabled it)...I believe you can do the same thing with the close button.

CMenu *pSysMenu = GetSystemMenu(FALSE);
ASSERT(pSysMenu != NULL);
VERIFY(pSysMenu->RemoveMenu(SC_MAXIMIZE, MF_BYCOMMAND));

Cheers,
Frank

Gumbercules? I love that guy!
Dr. Zoidberg

Avoiding multiple instances of an application.

John Uhlenbrock7-Aug-01 9:53

John Uhlenbrock

7-Aug-01 9:53

I've seen a few examples to avoid multiple instances of an application. In fact, there are a few of them here on code project. However, they all seem like a lot of code, when there is an easy solution like:

HANDLE hMutex = CreateMutex( NULL, TRUE, "MVD Load Utility" );

if( (hMutex == NULL)  ||  (GetLastError() == ERROR_ALREADY_EXISTS) )
{
  AfxMessageBox( "Two copies of this program are not allowed to run at the same time." );
  return FALSE;
}

Is there something wrong with this, I don't see why methods like this are necessary.

Re: Avoiding multiple instances of an application.

7-Aug-01 10:45

There is nothing wrong with that method and in fact, that is the most simple way possible.

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.