C / C++ / MFC

C^hris L^osinger7-Aug-02 17:46

C^hris L^osinger

7-Aug-02 17:46

you can only export a class from a DLL if you make an MFC (or "extension") DLL. and, then you can only use the DLL version of MFC in the project.

Frown | :(

-c

WWJD? JWRTFM.
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Anonymous7-Aug-02 18:37

Anonymous

7-Aug-02 18:37

thx. Am I bound to use MFC... or can I also make my own classes (it's a network class here) a DLL?

Paul M Watt7-Aug-02 21:07

Paul M Watt

7-Aug-02 21:07

Chris Losinger wrote:
you can only export a class from a DLL if you make an MFC (or "extension") DLL.

That is not true. Create a new Win32 DLL project in VC++ and select the option to export some symbols, a plain C++ class will be exported.

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

C^hris L^osinger7-Aug-02 21:28

C^hris L^osinger

7-Aug-02 21:28

???

i've been wrong on this point for years.

is it that you can only export MFC object from an MFC DLL?

-c

Conservative:
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-- Leo C. Rosten

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Paul M Watt8-Aug-02 11:45

Paul M Watt

8-Aug-02 11:45

Chris Losinger wrote:
is it that you can only export MFC object from an MFC DLL?

Think that is correct, because you need to have the CWinApp object to work with. However, a MFC extension DLL is a special type of DLL that uses the MFC applications CWinApp object instead of creating its own.

Then there is a regular DLL that can export functions and C++ objects.

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

Re: Creating DLL from C++ class ... plugin DLLs?

Paul M Watt7-Aug-02 21:13

Paul M Watt

7-Aug-02 21:13

create a win32 DLL project in VC++, and select the option that "exports some symbols". That should get you started. Here is the syntax to export a class:

class __declspec(dllexport) CClass {
public:
CClass(void);
};

The problem with exporting C++ classes is when you decide to expand the class for version 2.0 of your software. If you have different versions of a DLL with different class specifications in each DLL, then your programs may not work properly unless they have the properly matching DLL versions. This is the problem that COM attempts to solve.

If you are creating a program that may have different versions, then you may want to consider using COM instead of exporting classes from a DLL. This is just a suggestion.

If you have any more questions feel free to ask.

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

Anonymous7-Aug-02 21:21

Anonymous

7-Aug-02 21:21

kilowatt wrote:
If you are creating a program that may have different versions, then you may want to consider using COM instead of exporting classes from a DLL. This is just a suggestion.

If you have any more questions feel free to ask.

thanks, I think I'm ready to start. Smile | :)

Currently I do not plan to use different versions of a class.

Another thing I might implement is checking for "plugin" DLLs (all in same format, but with different functionality, normal C is fine here). For example a file provider1.dll, provider2.dll, etc... if they exist I would like to use them? Winamp uses this kind of DLL "plugins", but I don't know how it works.

TrackPopupMenu & WM_MENURBUTTONUP

GregH7-Aug-02 17:31

GregH

7-Aug-02 17:31

Is there a way to programatically cancel/close a menu that was displayed using TrackPopupMenu?

I am displaying a menu using TrackPopupMenu. When that menu is rt-clicked, I handle the WM_MENURBUTTONUP message and create a new popup context menu by calling TrackPopupMenu with the TPM_RECURSE flag set. I would like all the menus to close when a selection is made from the context menu, but have not found a way to do so. Currently only the context menu is closed, not the original menu. Any ideas on how to force it to close as well?

Thanks,

Greg

Re: TrackPopupMenu & WM_MENURBUTTONUP

Michael Dunn7-Aug-02 17:40

Re: TrackPopupMenu & WM_MENURBUTTONUP

7-Aug-02 17:40

I believe sending a WM_CANCELMODE to the parent window of the menus will do the trick.

--Mike--
Just released - RightClick-Encrypt v1.3 - Adds fast & easy file encryption to Explorer
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GregH7-Aug-02 17:53

GregH

7-Aug-02 17:53

That did it. Thanks!

a very simple question.about removing starting bytes from a char*

nss7-Aug-02 17:28

Re: a very simple question.about removing starting bytes from a char*

7-Aug-02 17:28

I have a blob that i retreived in a char* buffer, and it has access header stuff for 78 starting bytes. I want to remove these. whats the simplest way of doing this. I know the total length. i tried:

//	CString tmpstr(pBuf);
//	tmpstr.TrimRight(lDataLength-78);
//	memcpy(pBuf,tmpstr,lDataLength-78);

but it crashes at the memcpy. The pBuf I got from doing :

SafeArrayAccessData(varBLOB.parray,(void **)&pBuf);

Its the first 78 bytes of pBuf I want to get rid of.

Thanks,
ns

Michael Dunn7-Aug-02 17:43

Wow!!!! Thanks a million!!

7-Aug-02 17:43

memmove ( pBuf, pBuf+78, DataLength-78 );

You need to use memmove() because the source and dest ranges overlap.

--Mike--
Just released - RightClick-Encrypt v1.3 - Adds fast & easy file encryption to Explorer
My really out-of-date homepage
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nss7-Aug-02 18:04

Re: Wow!!!! Thanks a million!!

7-Aug-02 18:04

Gosh! That was like magic!! I couldnt believe it when I used your memmove and my images showed up!!!!I cant thank you enough!!!!!
Big Grin | :-D

Christian Graus7-Aug-02 18:28

Christian Graus

7-Aug-02 18:28

I don't think you even need to do that. If you have a char * called szRodney and you want to skip the first four characters, then

char * szEy = szRodney+4;

should do it, just don't forget to delte szRodney and NOT szEy.

Christian

We're just observing the seasonal migration from VB to VC. Most of these birds will be killed by predators or will die of hunger. Only the best will survive - Tomasz Sowinski 29-07-2002 ( on the number of newbie posters in the VC forum )

Cats, and most other animals apart from mad cows can write fully functional vb code. - Simon Walton - 6-Aug-2002

Re: a very simple question.about removing starting bytes from a char*

[James Pullicino]7-Aug-02 22:03

[James Pullicino]

7-Aug-02 22:03

One way to do it is:

int bytestoskip = 78;<br />
void *pBuf;<br />
SafeArrayAccessData(varBLOB.parray,(void **)&pBuf);<br />
char *szStr = (char *)pBuf + bytestoskip;

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Re: a very simple question.about removing starting bytes from a char*

nss7-Aug-02 22:37

Re: a very simple question.about removing starting bytes from a char*

7-Aug-02 22:37

Great! But a nagging question. I'm new to pointers. Now ,I thought that when you declare something as char* you have to do a new to allocate memory before you can use it. Yet in the SafeArrayAccessData and also your *szStr, all we have is the pointer declaration, but no memory allocated for its contents. Sorry if this is an obvious question.
Thanks for the nifty suggestion.
ns

[James Pullicino]11-Aug-02 3:07

[James Pullicino]

11-Aug-02 3:07

A SafeArray has the data allocated somewhere in its internal buffer. When you call SafeArrayAccess Data, the interal buffer is locked and a pointer to it is returned to you. This means that you do not have to copy the data, but you'll have to keep the safearray locked. Remember to call SafeArrayUnaccessData when you're done with the pointer!

James

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Forgot Password?

Re: a very simple question.about removing starting bytes from a char*

nss11-Aug-02 3:18

11-Aug-02 3:18

Ah! Thank you! ns

Dumb Question

Nick Parker7-Aug-02 16:46

7-Aug-02 16:46

Ok, I work with VB professionally, however I am about to make the jump into working on a possible project using MFC (applaud later Smile | :)

). I know this may sound like a dumb question but if I wanted to have a button show what a dialog window to open a file I know in VB we use the CommonDialog component. What do you do for MFC? I was looking around and I can see that you can insert a resource but that wasn't very clear to me. Can someone point me in the right direction, thanks in advance?

Michael Dunn7-Aug-02 17:45

7-Aug-02 17:45

I think you're talking about the standard file open dialog? MFC has CFileDialog.

--Mike--
Just released - RightClick-Encrypt v1.3 - Adds fast & easy file encryption to Explorer
My really out-of-date homepage
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Nick Parker7-Aug-02 18:05

7-Aug-02 18:05

Michael Dunn wrote:
I think you're talking about the standard file open dialog? MFC has CFileDialog.

Thanks Mike,
That's exactly what I was looking for. Smile | :)

I tried to do

CFileDialog cf;
cf.ShowWindow();

but I get an error saying "'CFileDialog' : no appropriate default constructor available" Confused | :confused:

Michael Dunn7-Aug-02 18:25

7-Aug-02 18:25

RTFM

The CFileDialog constructor has one manadatory parameter, a BOOL indicating whether it's for opening (TRUE) or saving (FALSE). So something like:

CFileDialog dlg ( TRUE );
 
  if ( IDOK == dlg.DoModal() )
    {
    CString sSelectedFile = dlg.GetPathName();
    }

You use DoModal() to show a modal dialog.

--Mike--
Just released - RightClick-Encrypt v1.3 - Adds fast & easy file encryption to Explorer
My really out-of-date homepage
Sonork-100.19012 Acid_Helm