ATL / WTL / STL

Need to transfer a callback function pointer?

28-Jan-04 17:32

Thank you very much.

I will try it.

-Freehawk

freehawk26-Jan-04 13:40

26-Jan-04 13:40

Hello everyone:
I want to transfer a function pointer from a WTL project to a MFC dll.
Do I need to make the function as a CALLBACK function?
How to transfer it?

-Freehawk

Jörgen Sigvardsson27-Jan-04 8:51

27-Jan-04 8:51

Through a function call perhaps? How would you do it otherwise?

Just define the function pointer type in a header file which the MFC dll and WTL project has access to during compile time. And add a function in the MFC dll which can deliver the function pointer.

I.e.:

typedef void (*FuncPtr)(type, type2, type3);
void InstallFunctionCallback(FuncPtr fptr);

And implement InstallFunctionCallback accordingly in your MFC dll.

--
Try walking in my shoes. You stumble in my footsteps.

freehawk27-Jan-04 15:05

27-Jan-04 15:05

Thank you for the reply.

I finished it, but I have not made the function as a callback function.
could you tell me what difference is between a function and a callback function translated
to dll as a function pointer?

-Freehawk

Jörgen Sigvardsson27-Jan-04 21:05

27-Jan-04 21:05

freehawk wrote:
tell me what difference is between a function and a callback function translated
to dll as a function pointer?

There is no difference really. Callback is just a semantic label for programmers.

--
Try walking in my shoes. You stumble in my footsteps.

freehawk27-Jan-04 23:40

Allocate byte array in ATL server

27-Jan-04 23:40

Thank you for the reply.

I did it.

-Freehawk

C^hris L^osinger26-Jan-04 11:40

26-Jan-04 11:40

I need to allocate and fill a large block of bytes in an ATL object, then pass that memory back to the client, which can delete it when it wants to.

i tried this:

<br />
[id(3), helpstring("method MFIGetFrame")] HRESULT MFIGetFrame([in] ULONG FrameIdx, [out] unsigned char **FrameArray, [out,retval] ULONG* Retval);<br />

but the COleDispatchDriver wrapper returns DISP_E_BADVARTYPE, because it doesn't know what to do with the "unsigned char **" .

i've tried using:

[id(3), helpstring("method MFIGetFrame")] HRESULT MFIGetFrame([in] ULONG FrameIdx, [out] SAFEARRAY(unsigned char)*FrameArray, [out,retval] ULONG* Retval);<br />

but the compiler keeps giving me: "error C2061: syntax error : identifier 'tagSAFEARRAY'".

i'm using VS.Net, which seems to make everything twice as hard as it needs to be.

any ideas?

ClickPic | ImgSource | CheeseWeasle

Jörgen Sigvardsson26-Jan-04 13:03

26-Jan-04 13:03

First, if you are returning an array in COM/IDL, you need to make it "conformant". You do that by indicating the number of elements in your array. I.e.:

HRESULT MFIGetFrame([in] ULONG FrameIdx, [out] ULONG* ArraySize, [out, size_is(1, *ArraySize)] unsigned char** FrameArray, [out, retval] ULONG* Retval)

At least that's what Essential IDL by Martin Gudgin told me last night. Smile | :)

As for the SAFEARRAY business, have you tried importing oaidl.idl? import "oaidl.idl"; It should be imported by default if I'm not mistaken though. Unsure | :~

--
Try walking in my shoes. You stumble in my footsteps.

C^hris L^osinger26-Jan-04 13:18

26-Jan-04 13:18

Jörgen Sigvardsson wrote:
have you tried importing oaidl.idl? import "oaidl.idl";

i tried that. but the error is actually happening in the "__interface" section of the ATL object's .H header (not in the IDL). apparently VC7 puts the IDL stuff right in the .H file, instead of an external IDL... ?
and, i can't figure out how to do an import in that __interface section.

ClickPic | ImgSource | CheeseWeasle

Jörgen Sigvardsson26-Jan-04 13:06

26-Jan-04 13:06

Just out of curiosity.. if you are calling the object using COleDispatchDriver, why not call using the vtable instead? Or is the interface a pure dispinterface, and you cannot in any way make the interface dual?

--
Try walking in my shoes. You stumble in my footsteps.

C^hris L^osinger26-Jan-04 13:19

26-Jan-04 13:19

Jörgen Sigvardsson wrote:
why not call using the vtable instead?

never done that before. i've always used COleDispatchDriver (and the project i'm doing this for is designed to use them).

i'm about to scrap the whole COM/ATL thing and just go back to plain old C-interfaced DLLs. ATL is far more trouble than it's worth.

ClickPic | ImgSource | CheeseWeasle

Lim Bio Liong27-Jan-04 6:08

Lim Bio Liong

27-Jan-04 6:08

Hello Chris,

Don't give up yet, Chris Smile | :)

.

>> ... i've always used COleDispatchDriver

Looks like your COM Server is meant to be IDispatch-based or dual interfaced. I did some experiments based on your sample code and came up with the following :

interface IMFIObject : IDispatch
{
[id(1), helpstring("method MFIGetFrame")] HRESULT MFIGetFrame([in] long FrameIdx, [out] VARIANT *pFrameArray, [out,retval] long* Retval);
};

In essence, I changed your second parameter from :

[out] unsigned char **FrameArray

and

[out] SAFEARRAY(unsigned char)*FrameArray

to :

[out] VARIANT *pFrameArray

This is how I implemented the method :

STDMETHODIMP CMFIObject::MFIGetFrame(long FrameIdx, VARIANT *pFrameArray, long *Retval)
{
// TODO: Add your implementation code here
LPBYTE lpbyToReturn = NULL;
SAFEARRAY* lpSafeArrayOfBytes = NULL;

lpbyToReturn = (LPBYTE)malloc(1024);

memset (lpbyToReturn, 'B', 1024);

// Wrap up lpbyToReturn in a SAFEARRAY.
CreateSafeArrayFromBytes
(
(LPBYTE)lpbyToReturn,
(ULONG)1024,
(SAFEARRAY**)&lpSafeArrayOfBytes
);

if (lpSafeArrayOfBytes)
{
// Note well that this function should always return a
// pointer to what is logically returned.
V_VT(pFrameArray) = VT_ARRAY | VT_UI1;
V_ARRAY(pFrameArray) = lpSafeArrayOfBytes;
}

if (lpbyToReturn)
{
free (lpbyToReturn);
lpbyToReturn = NULL;
}

*Retval = 1024;

return S_OK;
}

Here is a summary of what happens in the function :

1. I allocate an array of 1024 bytes and point to it via "lpbyToReturn". The number 1024 is not important. I simply wanted to "allocate and fill a large block of bytes in an ATL object" which is also what you wanted to achieve.

2. I then set all bytes in the array to the letter 'B'. This is done for verification purposes only.

3. I then create a SAFEARRAY and copy the data from the "lpbyToReturn" array to the SAFEARRAY.

4. I then take the second parameter "pFrameArray", which is a pointer to a VARIANT, and make it a valid VARIANT which holds a SAFEARRAY of BYTEs and make the VARIANT point to the newly created SAFEARRAY.

5. Note that I will now need to free the memory of the original array "lpbyToReturn". This is because the SAFEARRAY already contains the same BYTE values in "lpbyToReturn" .

6. Note that I do not free the SAFEARRAY because this is the memory block that is passed back to the client and the client is free to delete it whenever it wants to.

By the way, Chris, I've also supplied the source codes to CreateSafeArrayFromBytes() :

long CMFIObject::CreateSafeArrayFromBytes
(
LPBYTE lpbyBytes,
ULONG ulSize,
SAFEARRAY** ppSafeArrayReceiver
)
{
HRESULT hrRetTemp = S_OK;
SAFEARRAY* pSAFEARRAYRet = NULL;
SAFEARRAYBOUND rgsabound[1];
ULONG ulIndex = 0;
long lRet = 0;

// Initialise receiver.
if (ppSafeArrayReceiver)
{
*ppSafeArrayReceiver = NULL;
}

if (lpbyBytes)
{
rgsabound[0].lLbound = 0;
rgsabound[0].cElements = ulSize;

pSAFEARRAYRet = (SAFEARRAY*)SafeArrayCreate
(
(VARTYPE)VT_UI1,
(unsigned int)1,
(SAFEARRAYBOUND*)rgsabound
);
}

for (ulIndex = 0; ulIndex < ulSize; ulIndex++)
{
long lIndexVector[1];

lIndexVector[0] = ulIndex;

SafeArrayPutElement
(
(SAFEARRAY*)pSAFEARRAYRet,
(long*)lIndexVector,
(void*)(&(lpbyBytes[ulIndex]))
);
}

if (pSAFEARRAYRet)
{
*ppSafeArrayReceiver = pSAFEARRAYRet;
}

return lRet;
}

Now, over to client code. I made sure that my client code will also use the COleDispatchDriver class :

void CVCTestDlg::OnBnClickedButtonGetdynamicarrayfromobject()
{
// TODO: Add your control notification handler code here
IDispatch* pIDispatch = NULL;
COleDispatchDriver ole_disp_driver;
SAFEARRAY* pSafeArrayOfBytes = NULL;

m_spIMFIObject -> QueryInterface (IID_IDispatch, (void**)&pIDispatch);

if (pIDispatch)
{
long lRet = 0;
long lRet2 = 0;
BYTE byParamInfo[2 * 2 + 1];
VARIANTARG pVar;

VariantInit(&pVar);
VariantClear(&pVar);

ole_disp_driver.AttachDispatch(pIDispatch, FALSE);
sprintf ((LPTSTR)byParamInfo, TEXT("%s%s"), VTS_I4, VTS_PVARIANT);
ole_disp_driver.InvokeHelper(0x01, DISPATCH_METHOD, VT_I4, (void*)&lRet, byParamInfo, 1, &pVar);
pIDispatch -> Release();
pIDispatch = NULL;

pSafeArrayOfBytes = pVar.parray;
}

if (pSafeArrayOfBytes)
{
SafeArrayDestroy (pSafeArrayOfBytes);
pSafeArrayOfBytes = NULL;
}

return;
}

Notice that I defined a pointer to a SAFEARRAY object "pSafeArrayOfBytes" which will be filled by the MFIGetFrame() method which is of ordinal 0x01 in my example.

At the end of the function, I will actually delete the SAFEARRAY :

if (pSafeArrayOfBytes)
{
SafeArrayDestroy (pSafeArrayOfBytes);
pSafeArrayOfBytes = NULL;
}

I hope that the above code will be useful to you. Email me if you should want the full scource codes to the above sample. My email address is :

bllim@singnet.com.sg

Best Regards,
Bio.

C^hris L^osinger27-Jan-04 8:59

27-Jan-04 8:59

Wow, what a great response! Thanks!

ClickPic | ImgSource | CheeseWeasle

Problem compiling ATL minDependency Visual .NET 2003

Lim Bio Liong27-Jan-04 15:47

Lim Bio Liong

27-Jan-04 15:47

Hello Chris,

You're most welcome, Chris. I strongly believe that what you are trying to accomplish -is- achievable. Just remember to use OLE-Automation-compatible types for the parameters in your interface methods. Where all else fails, VARIANTs usually help.

Contact me again if you need further clarifications, Chris.

Best Regards,
Bio.

Wim Jans26-Jan-04 10:36

Wim Jans

26-Jan-04 10:36

Hello,

I have a problem compiling a project using the MinDependency option.
It gives me all kind of linke errors like these

<br />
Linking...<br />
LIBCMT.lib(crt0dat.obj) : error LNK2005: __osplatform already defined in atlmincrt.lib(atlinit.obj)<br />
LIBCMT.lib(crt0dat.obj) : warning LNK4006: __osplatform already defined in atlmincrt.lib(atlinit.obj); second definition ignored<br />
   Creating library .\ReleaseMinDependency/myproj.lib and object .\ReleaseMinDependency/myproj.exp<br />
LIBCMT.lib(crt0.obj) : error LNK2019: unresolved external symbol _main referenced in function _mainCRTStartup<br />
.\ReleaseMinDependency/myproj.dll : fatal error LNK1120: 1 unresolved externals<br />

Now, if I understand it correctly, this is because _ATL_MIN_CRT is defined.
I goto the project properties, set 'Minimize CRT usage in ATL' to No and 'Use of ATL' to Statically linked.

When I cross check with C/C++ Preprocessor I see _ATL_MIN_CRT is gone from the Inherited Values in the 'Preprocessor Definitions' property.

Now, when I compile and when the linkstep failed, I check the build.log and surprisingly I see the /D "_ATL_MIN_CRT" flag.
Did I do something wrong? Do other options (/GX) flag automatically add it to the cl.exe parameters?

Even when I check the C/C++ commandline in the project preoperties tab, it is not there.

Any clue?

Thanks

Wim

WTL Helper class: Message Map unused

peterchen26-Jan-04 9:00

peterchen

26-Jan-04 9:00

I'm trying to develop a WTL helper class, that does handle some extra messages, like this:

template <class BASE>
class CInplaceCtrl : public BASE
{
   BEGIN_MSG_MAP(CInPlaceCtrl<BASE>)
      MESSAGE_HANDLER(WM_KEYDOWN, OnInplaceEditKeydown)
      MESSAGE_HANDLER(WM_KILLFOCUS, OnInPlaceEditKillfocus)
      CHAIN_MSG_MAP(BASE)
   END_MSG_MAP()
   // ...
};

An instance is created as

CInplaceCtrl<CEdit> m_edInplace; // that's actually a dialgo class member
m_edInplace.Create( /* HWND of list control */, rect, ....); // in LVN_ITEMACTIVATE

The edit is created ok, but the message map seems not to be processed at all.
What to do?

Flirt harder, I'm a coder.

mlog || Agile Programming | doxygen

Re: WTL Helper class: Message Map unused

Jörgen Sigvardsson26-Jan-04 9:26

Re: WTL Helper class: Message Map unused

26-Jan-04 9:26

Try using DECLARE_WND_SUPERCLASS(_T("Your new class name"), _T("BASE class name")) and derive from CWindowImpl<CInplaceCtrl, BASE>.

That works when overriding the behaviour of system classes such as buttons, list views etc. Dunno if it works on a CWindowImpl-based class. I see no direct reasons it shouldn't though.

Also, remember that you're getting the first go at all events. If you intend to pass the event to the base class, either set the fourth argument (BOOL&) to FALSE, or call DefWindowProc() to let the base message map dispatch the event.

--
<british-accent>Pass the jam, would you?

peterchen26-Jan-04 9:44

peterchen

26-Jan-04 9:44

Thanks!
Works seemingly perfect without the DECLARE_WND_SUPERCLASS

really necessary?

Flirt harder, I'm a coder.

mlog || Agile Programming | doxygen

Re: WTL Helper class: Message Map unused

Jörgen Sigvardsson26-Jan-04 9:52